.If'w-I? '°.u-H J m . : IIEIMI\V'4 .....- ‘hgpbl‘lilli'v Ht ,.. t...“ m 1: . ..~. . :1) '* 7i LIBRARY Michigan State University This is to certify that the dissertation entitled - QTL ANALYSIS OF FRUIT COLOR AND ESTIMATION OF GENETIC DIVERSITY USING DNA MARKERS IN SWEET CHERRY (Prunus avium L.) presented by SUNETH SITHUMINI SOORIYAPATHIRANA has been accepted towards fulfillment of the requirements for the Ph.D degree in Plant Breeding, Genetics and Biotechnology Majér’ Profefis’ Signature 3%,: ”3 m 7 Date MSU is an Affirmative Action/Equal Opportunity Employer nu-u—--.-.-.-.-.-.-.—o-.-a-.-.-.->—---o-u-.--.-¢-.--.--.---.--.—a---.---.. -.-«-.--.-.--.-.-.-.--c-n--.--- PLACE IN RETURN Box to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 5/08 K:/Proleoc&Pres/CIRCIDateDue.indd QTL ANALYSIS OF FRUIT COLOR AND ESTIMATION OF GENETIC DIVERSITY USING DNA MARKERS IN SWEET CHERRY (Prunus avium L.) By Suneth Sithumini Sooriyapathirana A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Plant Breeding, Genetics and Biotechnology 2009 ABSTRACT QTL ANALYSIS OF FRUIT COLOR AND ESTIMATION OF GENETIC DIVERSITY USING DNA MARKERS IN SWEET CHERRY (Prunus avium L.) By Suneth Sithumini Sooriyapathirana Fruit color is an important indicator of sweet cherry fruit maturity and distinguishes two major market classes, e. g. yellow skin and fruit with a pink blush on the skin, and dark mahogany colored skin and flesh. Yet, within these extremes, there is a continuum of flesh and skin color types. The genetic control of skin and flesh color in sweet cherry was investigated using a QTL approach with a population derived from a cross between parents representing the two color extremes. Skin and flesh colors were measured from the progeny using a qualitative color card rating in 2006, 2007 and 2008. In 2008, color was also evaluated quantitatively for lightness (L*), redness (a*), and yellowness (b*). The skin and flesh color card ratings for the three years were significantly correlated (P<0.0001) and therefore only the 2008 data were used in the genetic analyses. Progeny segregations for the color measurements (card, L*, a*, b*) did not fit normal distributions; instead the distributions were skewed towards the skin color of the dark-skinned parent. A major QTL for skin and flesh color was identified on Linkage Group (LG) 3 and three other QTLs for skin and flesh color were identified on LGS, LG6 and LG8. However, the consistent significance of the QTL identified on LG3 suggests the presence of a major regulatory gene for fruit color development. The genetic diversity of sweet cherry (Prunus avium L.) germplasm historically used in the breeding programs of Pacific North West region in North America was studied in comparison to a subset of European sweet cherry landraces and a wild cherry (P. avium) selection to test the hypothesis of genetic founder effect that occurred when early settlers brought selected subset of sweet cherry germplasm from Europe to the New World. Pacific North West sweet cherry germplasm was defined as a set of 28 landraces, parents and released cultivars. A subset of seven European sweet cherry landraces and a single wild cherry selection were used for the comparison. The genotypic data for all 36 sweet cherry selections were recorded for 77 DNA markers. A total of 300 alleles were detected for 77 markers with an average of four alleles per locus. A total of 52 unique alleles were identified and 40 of them were not present in the Pacific North West sweet cherry germplasm. The 50% of the total alleles detected were rare alleles and 30% of the total rare alleles were not detected in the Pacific North West sweet cherry germplasm. The European landraces were distantly related at 25% of genetic dissimilarity value but Pacific North West sweet cherry parents and cultivars were separated only at 8% of genetic dissimilarity value showing the low level of diversity compared to European sweet cherry landraces and the wild cherry selection. This study shows that Pacific North West sweet cherry germplasm had been subjected to genetic founder effect and implies that the introduction of new germplasm from Europe is necessary to broaden the genetic diversity in the Pacific North West sweet cherry germplasm. COPYRIGHT SUNETH SITHUMINI SOORIYAPATHIRANA 2009 DEDICATION To my wife Chamila Kumari Pathirana ACKNOWLEDGEMENTS I am enormously grateful to my major professor Dr. Amy F. Iezzoni for accepting me to her research group, for her supervision, inspiration, courteous help and fmancial assistance throughout my study. I express my deepest gratitude to Dr. James F. Hancock for his guidance, motivation, friendliness and financial assistance. I am very grateful to Dr. J. Mitchell McGrath for his insight and teaching me the complex aspects of molecular biology and genomics. I thank and sincerely appreciate Dr. Dechun Wang for teaching me the statistical genetics and his directions throughout my research project. I appreciate and thank Audrey M. Sebolt for her expertise, help and kindness. I give special thanks to Peter W. Callow for his support, generosity and friendliness. I am very grateful to Dr. Janet M. Lewis and Karolyn A. Terpstra for offering me teaching assistantships. I appreciate the support rendered by Sue A. Hammar, Dr. Guorong Zhang, Dr. Veronica A. Vallejo, Dr. Guo-Qing Song and Travis L. Stegmeir. I am also grateful to the administrative staff, Lorri K. Busick, Rita M. House, Sherry M. Mulvaney, Joyce T. Lockwood and Sharon Roback for their support. I also thank all the faculty, staff and students of the Plant Breeding, Genetics and Biotechnology Graduate Program at Michigan State University for their support, guidance and companionship throughout my graduate student life. I sincerely thank Dr. S. H. P. Parakrama Karunaratne and Dr. Preminda Sarnaraweera, Faculty of Science, University of Peradeniya, Sri Lanka for their vi motivation, advices and granting study leave for me to undertake graduate research studies at MSU. I warmly thank my wife, Chamila Kumari Pathirana for her unwavering support, guidance, motivation and patience. Her constant nurture and inspiration were the key forces behind my success. I dedicate this thesis to Chamila for her love and affection. Finally I graciously mention and thank my wife Chamila and our two little sons, Saritha Hansana and Ranuga Sanhitha, for keeping my life happy and pleasant. vii TABLE OF CONTENTS LIST OF TABLES ................................................................................................... x LIST OF FIGURES ................................................................................................. xiii LITERATURE REVIEW ....................................................................................... 1 GENETICS OF FRUIT SKIN AND FLESH COLOR IN SWEET CHERRY ..... 2 Importance of fruit color in cherry industry .................................................. 2 Variability of fruit color in sweet cherry ...................................................... 2 Genetics of fruit color in sweet cherry .......................................................... 3 Fruit color pigments in sweet cherry ............................................................ 3 Factors affecting color development in sweet cherry ................................... 3 Variability of fruit color in apple .................................................................. 4 Genetics of fruit color in apple ..................................................................... 4 Biochemistry and molecular genetics of fruit color in apple ........................ 5 Fruit color studies in other rosaceous crops .................................................. 6 Chapter one: Goal ......................................................................................... 8 LTERATURE CITED .................................................................................. 9 GENETIC DIVERSITY IN SWEET CHERRY GERMPLASM .......................... 13 Background ................................................................................................... 13 Origin and geographical range ...................................................................... 13 Genetic diversity ........................................................................................... 14 Breeding ........................................................................................................ 1 5 Chapter two: Goal ......................................................................................... 16 LITERATURE CITED ................................................................................. 17 CHAPTER ONE: QTL ANALYSIS OF FRUIT SKIN AND FLESH COLOR IN SWEET CHERRY (Prunus avium L.) ................... 19 INTRODUCTION ............................................................................................... 20 MATERIALS AND METHODS ........................................................................ 22 Plant material ................................................................................................ 22 Fruit sampling and evaluation ....................................................................... 22 Statistical analysis for color measurements .................................................. 26 QTL analysis ................................................................................................. 26 RESULTS AND DISCUSSION ......................................................................... 28 Color data ...................................................................................................... 28 Color development ........................................................................................ 33 Data distribution ............................................................................................ 35 viii QTL analysis ................................................................................................. 42 QTL haplotypes ............................................................................................ 52 Epistasis ........................................................................................................ 61 CONCLUSION ................................................................................................... 71 LITERATURE CITED ....................................................................................... 72 CHAPTER TWO: GENETIC DIVERSITY ANALYSIS OF SWEET CHERRY (Prunus avium L.) CULTIVARS USING DNA MARKERS .................................................................... 75 INTRODUCTION .............................................................................................. 76 MATERIALS AND METHODS ....................................................................... 78 Plant materials .............................................................................................. 78 DNA extraction and genotyping ................................................................... 78 Data analysis ................................................................................................. 79 RESULTS AND DISCUSSION ........................................................................ 82 Unique and rare alleles ................................................................................. 82 Allele diversity and cultivar heterozygosity ................................................. 82 Genetic diversity structure ............................................................................ 106 Graphical genotypes for sweet cherry cultivars ........................................... 109 A panel of cultivars for SNP discovery for P. avium ................................... 144 Related studies on genetic diversity in Prunus ............................................ 147 Marker polymorphism .................................................................................. 151 A panel of DNA markers for P. avium DNA fingerprinting ........................ 154 Use of DNA markers for diversity studies ................................................... 154 CONCLUSION ............................................................................................ 156 LITERATURE CITED ................................................................................. 157 ix LIST OF TABLES Table 1.1: Description of the color card categories for fruit skin color in sweet cherry used for QTL analysis ................................................................. 24 Table 1.2: Description of the color card ratings for fruit flesh color in sweet cherry used in the QTL analysis .............................................................. 25 Table 1.3: Pearson’s correlation coefficients for skin color 1 (SCl), skin color 2 (SC2), and flesh color (FC) card readings from the NY X EF progeny in 2006, 2007 and 2008 ............................................................. 30 Table 1.4: Pearson’s correlation coefficients for skin color 1 (SCI), skin color 2 (SC2) and flesh color (FC) card and L*, a*, and b* values for NY >< EF progeny evaluated in 2008 .............................................................. 31 Table 1.5: Means and standard deviations for skin color 1 (SCI), skin color 2 (SC2), and flesh color (FC) values for EF and NY in 2008 .................... 32 Table 1.6: The progression of fruit skin and flesh color over harvest data for blush and mahogany classes of NY54 x EF progeny for year 2008 ....... 34 Table 1.7: Summary statistics and heritability of color data for year 2008 ............. 41 Table 1.8: QTLs for color card values, L*, a* and b* for SC], SC2 and FC identified in the NY >< EF F1 population in 2008 data ............................ 44 Table 1.9: Definitions of parental haplotypes for five QTL regions on linkage groups 3, 5, 6 and 8 ................................................................................... 55 Table 1.10: Card and a* of skin color 1 (SCI), Card and b* of skin color 2 (SC2) and Card, L8 and b* of flesh color (F C) of different genotype classes for the major QTL on linkage group 3 at 53.7 cM. Numbers in parenthesis are the number of progeny individuals ........................... 56 Table 1.11: L* and b* of skin color 1 (SCI), L* and a* of skin color 2 (SC2) and a* of flesh color (FC) of different genotype classes for the minor QTL on linkage group 3 at ~21.0 cM. Numbers in parenthesis are the number of progeny individuals ............................... 57 Table 1.12: b* of skin color 1 (SCI) of different genotype classes for the QTL region on linkage group 6. Numbers in brackets are the number of progeny individuals ................................................................................ 58 Table 1.13: a* of flesh color (F C) of different genotype classes for the QTL region on linkage group 5. Numbers in brackets are the number of progeny individuals ................................................................................ 59 Table 1.14: a* of flesh color (FC) of different genotype classes for the QTL region on linkage group 8. Numbers in brackets are the number of progeny individuals ................................................................................ 60 Table 2.1: The Prunus avium groups, selections (wild, Non-PNW and PNW), their parents, origins, number of unique alleles (U A) and % of heterozygous loci (H) ............................................................................. 85 Table 2.2: The relative abundance of alleles with differing frequencies detected for 77 DNA markers ................................................................ 87 Table 2.3: The percentage of heterozygous loci (H) per linkage group .................... 88 Table 2.4: The possession of marker-alleles by sweet cherry selections - LG1 ........ 89 Table 2.5: The possession of marker-alleles by sweet cherry selections - LG2 ........ 90 Table 2.6: The possession of marker-alleles by sweet cherry selections - LG3 ........ 91 Table 2.7: The possession of marker-alleles by sweet cherry selections - LG4 ........ 92 Table 2.8: The possession of marker-alleles by sweet cherry selections - LG5 ........ 93 xi Table 2.9: The possession of marker-alleles by sweet cherry selections - LG6 ........ 94 Table 2.10: Table 2.11: Table 2.12: Table 2.13: Table 2.14: Table 2.15: The possession of marker-alleles by sweet cherry selections - LG7 ...... 95 The possession of marker-alleles by sweet cherry selections - LG8 ...... 96 The panel of selections/individuals for SNP detection in P. avium ....... 146 The comparison of number of alleles per SSR marker and heterozygosity (H) of three SSR between sweet and flowering cherries ................................................................................................... 148 The number of alleles detected for sweet and tart cherries for 6 SSR markers ........................................................................................... 150 Heterozygosity (H) and Polymorphic Information Content (PIC) of DNA markers used in the study ............................................................. 153 xii Figure 1.1: Figure 1.2: Figure 1.3: Figure 1.4: LIST OF FIGURES A-L Progeny frequency distribution of color traits measured in 2008 (A) SCI card. (B) SC2 card. (C) PC card. (D) SCI L*. (E) SC2 L*. (F) FC L*. (G) SCI a*. (H) SC2 a*. (1) PC a*. (J) SCI b*. (K) SC2 b*. (L) FC b*. EF and NY parental values are shown. A—D Locations of QTLs for color card and L*, a* and b* values for SCI (darkest location of the fruit skin), SC2 (lightest location of the fruit skin) and F C (flesh color) using the multiple QTL mapping method. The variability explained by QTL (R2%) is shown after the trait name of each QTL. 1-LOD and 2-LOD support intervals of each QTL are marked by thick and thin bars, respectively. Blank bars represent QTLs for color card QTLs. Black bars represent QTLs for L*. Bars filled with one sided hatch lines represent QTLs for a*. Bars filled with two sided hatch lines represent QTLs for b*. Only linkage groups including the QTLs are presented. (A) Linkage group 3, (B) Linkage group 5, (C) Linkage group 6, (D) Linkage group 8. LOD scores and the percentage variability explained by the QTLs (R2) are presented in the Table 1.8 ................................................................................. Locations of QTLs on LG3 for color card data of 2006, 2007 and 2008 for SCl (darkest location of the fruit skin), SC2 (lightest location of the fruit skin) and FC (flesh color) using the multiple QTL mapping method. Blank bars represent QTLs. 1-LOD and 2- LOD support intervals of each QTL are marked by thick and thin bars, respectively. The percentage variability explained by the QTL (R2) and the level of QTL significance in number of stars (***: LOD value significant at P < 0.05 genome wide, **: LOD value significant at P < 0.1 genome wide, * : The LOD value significant at P <0.05 individual linkage group wide, based on 1000 permutation tests) are shown with the QTLs. .......................... A-E. The two-way inter genomic region interactions between the major QTL and the minor QTL regions on LG3 (A) Inter loci interaction for SCl L* between PR41 and Ma066a (B) Inter loci interaction for SCl b* between PR41 and Ma066a (C) Inter loci interaction for SC2 L* between PR41 and Ma066a (D) Inter loci interaction for SC2 a* between PR41 and Ma066a (E) Inter loci interaction for F C a* between PR41 and Ma066a. Means denoted by same letter within each graph are not significantly different at xiii ...... 36 ...... 45 ...... 50 Figure 1.5: Figure 2.1: Figure 2.2: Figure 2.3: Figure 2.4: P < 0.05 (done using Least Squares Means, General Linear Model SAS 9.1). Units: L*, a* and b* (colorimeter reading) ............................ 63 A-C. The two-way inter genomic region interactions between the major QTL region on LG 3 and the other QTLs on LGs 5, 6 and 8. (A) Inter loci interaction for F C a* between PR41 on LG 3 and PS1H3 on LG8. (B) Inter loci interaction for PC a* between PR41 on LG 3 and BPPCT026 on LG5 (C) Inter loci interaction for SCI b"‘ between PR41 on LG 3 and UDP96-001 on LG6 Means denoted by same letter within each graph are not significantly different at P < 0.05 (done using Least Squares Means, General Linear Model SAS 9.1). Units: L*, a* and b* (colorimeter reading) ................................................................................................... 67 The number of unique and shared alleles identified in the three groups of sweet cherry used in the study; PNW: 28 cultivars historically used and released in the Pacific North West sweet cherry breeding programs, Non-PNW: seven sweet cherry cultivars from Europe that have not been used in the PNW sweet cherry breeding programs and Wild: one forest (mazzard) cherry (Prunus avium) selection (N Y54) ........................................................... 86 A-H. The different alleles for the markers and their relative presence in all the linkage groups for 36 sweet cherry selections {wild cherry (gray bar), PNW (white bar) and non-PNW (black bar) groups}. The arrows show the alleles that do not exist in the PNW sweet cherry cultivars and the names of the cultivars are indicated near the arrows. A: linkage group (LG) 1, B: LG2, C: LG3, D: LG4, E: LG5, F: LG6, G: LG7, H: LG8 .................................. 97 Dendrogram resulting from marker allele based genetic distance analysis of 36 sweet cherry selections. Cluster analysis used McQuitty linkage, Absolute Correlation Coefficient Distance (Minitab 15) ............................................................................................ 107 Figure 2.4: A-H Graphical genotypes for 36 sweet cherry cultivars. Eight linkage groups for each cultivar are shown with two homologous chromosomes for each linkage group. The marker positions in centi Morgan (cM) and marker names are shown on the left. In each cell, the allele in base pairs is shown for the SSR and gene based (PR markers and the allele name in xiv number is shown for the S-locus. 558 indicates a confirmed null allele and 8 indicates an unconfirmed null allele. “ -” represents the missing data. The blank cells represent the gaps in the linkage groups. (A) Linkage group 1, (B) Linkage group 2, (C) Linkage group 3, (D) Linkage group 4, (E) Linkage group 05, (F) Linkage group 6, (G) Linkage group 7, (H) Linkage group 8. Each linkage group has four pages of GGT to represent 36 sweet cherry selections in four separate pages. Page 1 for each linkage group: Wild cherry (N Y54) and non-PNW sweet cherry cultivars, Page 2 for each linkage group: second subset of PNW sweet cherry cultivars, Page 3 for each linkage group: third subset of PNW sweet cherry cultivars, Page 4 for each linkage group: fourth subset of PNW sweet cherry cultivars ................................................... 111 XV LITERATURE REVIEW GENETICS OF FRUIT SKIN AND FLESH COLOR IN SWEET CHERRY Importance of fruit color in cherry industry Fruit color is one of the most important traits in determining consumer demand in sweet cherry (Prunus avium L.). Dark mahogany colored sweet cherries are preferred in North America (Turner 2008) and Europe (Werrnund and Feame 2000) and blush colored sweet cherries are preferred in Asia (Miller et al. 1986). The color of fi'uit skin and flesh is also important to determine the maturity level of fruits (Facteau et al. 1983). Breeding for sweet cherry cultivars with desired fruit colors is challenging, because, the underlying genetics of skin and flesh color traits have not been studied in detail. Variability of fruit color in sweet cherry The phenotypic diversity of fruit skin and flesh color of sweet cherry is very high. Fruit skin and flesh colors range from dark mahogany skin and flesh (e. g. cultivar “Bing”) and yellow skin and flesh (e.g. cultivar “Gold”). There are blushed fruit cultivars with red/mahogany shades in yellow background and yellow flesh (e.g. cultivar “Rainier”). The classification of sweet cherry skin and flesh into color classes is dependent upon the level of fruit maturity. Dark skinned fruits get darker with time and their flesh follows the same pattern of the color development in skin. In blushed fruits, the red shades get more prominent in the skin and the flesh color remains unchanged with maturity. Genetics of fruit color in sweet cherry Classical genetic approaches were used to understand the genetics of fruit color in sweet cherry and postulated that the skin color is controlled by one major factor (Aa) and one minor factor (Bb) and incomplete dominant epistasis was also suggested for the interaction between A and B. Factor A was also proposed to be responsible for controlling the flesh color (F ogle 1958 and Schmidt 1998). The data from European breeding populations supported this genetic model (Hedtrich 1985; Georgiev 1985; Rodrigues et al. 2008; and Tobutt and Boskovic 1996). Fruit color pigments in sweet cherry The color of cherries, either sweet or tart (P. cerasus L.) is mainly due to anthocyanins. Red sweet cherry cultivars mainly contain Cyanidin-3-0-rutinoside (95% of total anthocyanin) and cyanidin-3-0-g1ucoside. Red sour cherry cultivars such as ‘Balaton’ and ‘Montmorency’ have mainly Cyanidin-3-0-glucosylrutinoside and cyaniding-3-0-rutinoside and minor quantities of cyanidin-3-0-glucoside. The blush cultivars have carotenoids such as beta-carotene (Mulabagal et al. 2009). Factors affecting color development in sweet cherry Fruit skin and flesh color is affected by environment to a certain degree. The environmental effect on the color development is higher in blush cherries than in dark mahogany colored cherries. Application of gibberellic acid has no significant impact on the fruit color in cherry (Horvitz 2003). In blush sweet cherries, UV light stimulates the anthocyanin synthesis (Arakawa 1993). This explains the fact that the blush cherries that are located inside the canopy are less colorful than the cherries on the outer canopy, as leaves absorb most of the UV light before reaching the interior canopy. Variability of fruit color in apple The fruit color of apple (Malus x domestica) is well studied, and as apple and cherry belong to the same family, Rosaceae, the recent advancements of fruit color genetics in apple are applicable to study the fruit color genetics in sweet cherry. Apple skin color has a wide array of phenotypic diversity ranging from green, yellow and dark purple. The shaded combinations of different colors can also be seen. Lancaster (1992) reported that combinations of carotenoids, chlorophyll and anthocyanins determine the various skin colors in apple. Genetics of fruit color in apple The postulated mechanisms for genetics of skin color in apple are not in common agreement. A single dominant gene model was suggested for dark red skin (Brown 1992 and Crane and Lawrence 1933). Klein (1958) found that anthocyanin stripes of apple skin color are controlled by one major gene. White and Lespinasse (1986) suggested two complementary genes, A and B. Later Lespinasse et al. (1988) proposed a three major gene model for determination of apple skin color. Schmidt (1988) postulated additional modifying factors. Biochemistry and molecular genetics of fruit color in apple The molecular studies on apple color genetics had started in the late 20th century. A RAPD marker was found to be linked to apple skin color (Cheng et al. 1996). Apple has Cynidin 3- O-galactoside as the major form of anthocyanin (Lancaster 1992, Tsao et al. 2003). Many genes associated with the anthocyanin biosynthetic pathway have been cloned from apple fruit skin; flavonone 3-hydroxylase (F3 H), dihydroflavonol reductase (DF R), anthocyanin synthase (ANS) and UDP-glucose flavonoid 3-Oglucosyltransferase (UFGT) (Honda et al. 2002, Kim et al. 2003). These genes have found to be light induced and highly expressed in red apple skins. Takos et al. (2006), Espley et al. (2007) and Ban et al. (2007) have shown that one or two MYB transcription factors are playing the central role in apple fruit skin color genetics. MdMYBA, a cDNA encoding a putative R2R3-MYB protein (Ban et al. 2007), regulated anthocyanin biosynthesis in apple skin, has a huge similarity to MdMYBl which was independently discovered by Takos et al. (2006). The only marked difference is that these two genes are differentially expressed at young stages of the fruit growth. Another MYB gene, MdMYBI 0 found by Espley et al. (2007) that has some significant differences in expression relative to MdMYBA or MdMYBI. Ban et al. (2007) speculated that there would be at least two MdMYB loci active in anthocyanin biosynthesis in apple skin. Polymorphism at the MdMYBa has been mapped to Linkage Group 9 in apple ‘Delicious’ (Ban et al. 2007). Chagne et al. (2007) found that red flesh and foliage color of apple co-segregated. The allele controlling the red color has been named as Rni, has been mapped along with MdMYBI 0 to a single locus Linkage Group 9 in apple. The expression of these MYB genes are UV light defendant and low temperature induced. Espley et al. (2009) showed that a rearrangement in the promoter region of MdMYBI 0, a microsatellite like structure with tandem repeats of 23-bp sequence caused red phenotype in apple flesh and foliage. This motif is a target for the MdMYBIO protein itself and hence provides an autocatalytic regulation. This autocatalytic regulation ensures the accumulation of MdMYBI 0 protein and accumulation of anthocyain throughout the plant. The MdMYB transcription factor closely interacts with bHLH, another transcription factor that regulates anthocyanin biosynthetic pathway genes. The specific genes targeted by transcription factor complexes in apple have not been found. In Arabidopsis and grapes, such targets have been reported (Borevitz et al. 2000, Tohge et al. 2005, Kobayashi et al. 2002). The molecular genetic information of these studies has an immense importance in studying the fruit color genetics of sweet cherry. Fruit color studies in other rosaceous crops Compared to the color work in apple, the skin color of peach and other rosaceous fruits has not been studied in detail. Fruit skin and flesh color of peach has very high phenotypic diversity; yellow to red skin and white to red flesh. Connors (1920) described that an allele, Y, that controls white flesh is dominant to yellow (y) flesh in peach. Beckman et a1. (2005) found allele, h, (highlighter) suppresses red color. The genetic correlation between Y and h is not known. Beckman and Sherman (2003) showed full red phenotype is controlled by fr. Dark red flesh is determined by a single gene, bf (Werner et al. 1998). Skin color trait has been mapped to linkage group six (Dirlewanger et al. 2004, Yamamoto et al. 2001). Peach color is mainly due to carotenoids and beta carotene is the main form of carotenoid followed by beta-cryptoxanthin (Gil et al. 2002). The correlation between carotenoid accumulation and the expression of carotenogenic genes in Japanese Apricot (P. armem'aca L.) has been established (Kita et al. 2007). Phytoene synthase-1 and lycopene B-cyclase expression is required for carotenoid accumulation. Decrease in lycopene e-cyclase expression and increase in lycopene B-cyclase causes a metabolic shift from synthesis of B-e-carotenoid to synthesis of B, [3 carotenoid with ripening progresses. Ethylene is important for the primary induction of Phytoene synthase-1. Kassim et al. (2009) mapped the polymorphisms of several transcription factors and candidate genes of anthocyanin biosynthetic pathway to QTLs in raspberry, Rubus idaeus L., another important rosaceous fruit species. The genetics of fruit color in rosaceous crops is a fast developing area and the advancements in apple, peach, apricot and raspberries could be applied to understand the fruit color genetics of other rosaceous crops such as sweet cherry. Chapter One: Goal The aim of the Chapter One was to identify the genomic regions that are associated with fruit skin and flesh color in sweet cherry. This study was the first attempt to utilize the Quantitative Trait Loci (QTL) approach to dissect the genes related to fruit color in cherry. The expected results would enable us to understand the genetic mechanisms of fruit color in cherry and will be useful in marker assisted breeding for sweet cherry varieties with desired fruit colors and to further unravel the molecular genetic basis of fruit color in sweet cherry. LITERATURE CITED Arakawa O (1993) Effect of ultraviolet light on anthocyanin synthesis in light-colored sweet cherry, cv. Sato Nishiki. 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Plant Journal 49:414—427 Facteau TJ, Chestnut NE, Rowe KE (1983) Relationship between fruit weight, firmness, and leaf/fruit ratio in Lambert and Bing sweet cherries. Can J Plant Sci 63:763—765 Fogle HW (1958) Inheritance of fruit color in sweet cherries {Prunus avium). J Heredity 49:294—298 Georgiev VS (1985) Some results with sweet cherry breeding in the research institute for fruit growing in Kustendil, Bulgaria. Acta Hortic 169:73—78 Gil MI, Tomas-Barberan FA, Hess-Pierce B, Kade, AA (2002) Antioxidant capacities, phenolic compounds, carotenoids, and vitamin C contents of nectarine, peach and plum cultivars from California. J Agric Food Chem 50:4976—4982 Hedtrich RT (1985) Sweet cherry breeding at the Swiss Federal Research Station I. Results of fruit characters and flowering period inheritance. Acta Hortic 169:51—62 Honda C, Kotoda N, Wada M, Kondo S, Kobayashi S, Soejima J, Zhang Z, Tsuda T, Moriguchi T (2002) Anthocyanin biosynthetic genes are coordinately expressed during red coloration in apple skin. Plant Physiol Biochem 40:955—962 Horvitz S, Godoy C, Lopez-Camelo AF, Yommi A (2003) Application of gibberellic acid to ‘Sweetheart’ sweet cherries: effects on fruit quality at harvest and during cold storage. Acta Hortic 628:31 1—3 16. 10 Kassim A, Poette J, Paterson A, Zait D, McCallum S, Woodhead M, Smith K, Hackett C, Graham J (2009) Environmental and seasonal influences on red raspberry anthocyanin antioxidant contents and identification of quantitative traits loci (QTL). Mol Nutr Food Res 532625—634 Kim SH, Lee JR, Hong ST, Yoo YK, An G, Kim, SR (2003) Molecular cloning and analysis of anthocyanin biosynthesis genes preferentially expressed in apple skin. Plant Sci 165:403—413 Kita M, Kato M, Ban Y, Honda C, Yaegaki H, Ikoma Y, Moriguchi T (2007) Carotenoid accumulation in Japanese apricot (Prunus mume Siebold & Zucc.): molecular analysis of carotenogenic gene expression and ethylene regulation. J Agric Food Chem. 55:3414—20 Klein LG (1958) The inheritance of certain fruit characters in apple. J Am Soc Hortic Sci 72: 1-14 Kobayashi S, Ishimaru M, Hiraoka K, Honda C (2002) MYB related genes of the Kyoho grape (Vitis labruscana) regulate anthocyanin biosynthesis. Planta 15: 924—933 Lancaster JE (1992) Regulation of skin color in apples. Crit Rev Plant Sci 10:487—502 Lespinasse Y, Fouillet A, Flick JD, Lespinasse J M, Delort F (1988) Contributions to genetic studies in apple. Acta Hortic 224:99—108 Miller DC, Casavant KL, Buteau RJ (1986) An analysis of Japanese consumer preferences for Pacific Northwest and Japanese sweet cherries. Research Bulletin XB Washington State University, Agricultural Research Center. pp1—15 Mulabagal V, Lang GA, DeWitt DL, Dalavoy SS, Nair MG (2009) Anthocyanin content, lipid peroxidation and cyclooxygenase enzyme inhibitory activities of sweet and sour cherries. J Agric Food Chem. 57:1239—46 Rodrigues LC, Morales MR, Femandes AJ B and Ortiz JM (2008) Morphological characterization of sweet and sour cherry cultivars in a germplasm bank at Portugal. Genet Resour Crop Evol 55:593—601 11 Schmidt H (1988) The inheritance of anthocyanin in apple fruit skin. Acta Hortic 224:89— 97 Schmidt H (1998) On the basis of fruit color in sweet cherry. Acta Hortic 468277—81 Takos AM, Jaffe FW, Jacob SR, Bogs J, Robinson SP, Walker AR (2006) Light-induced expression of a MYB gene regulates anthocyanin biosynthesis in red apples. Plant Physiol 142:1216—1232 Tobutt KR, Boskovic R (1996) A cherry gene database. Acta Hortic 410:147—154 Tohge T, Nishiyama Y, Hirai MY, Yano M, Nakajima J, Awazuhara M, Inoue E, Takahashi H, Goodenowe DB, Kitayama M, Noji M, Yamazaki M, Saito K (2005) Functional genomics by integrated analysis of metabolome and transcriptome of Arabidopsis plants over-expressing an MYB transcription factor. Plant Journal 422218-235 Tsao R, Yang R, Young J C, Zhu H (2003) Polyphenolic profiles in eight apple cultivars using high-performance liquid chromatography (HPLC). J Agric Food Chem 21 :6347—6353 Turner J, Seavert C, Colonna A, Long LE (2008) Consumer sensory evaluation of sweet cherry cultivars in Oregon, USA. Acta Hortic 795:781—786 Wermund U, Feame A (2000) Key challenges facing the cherry supply chain in the UK. Acta Hortic 536:613—624 Werner DJ, Creller MA, Chaparro JX (1998) Inheritance of blood flesh in peach. HortScience 33: 1243—1246 White AG, Lespinasse Y (1986) The inheritance of fruit color in apple (Malus pumila Mill.). Agronomic 6: 105—108 Yamamoto T, Shimada T, Imai T, Yaegaki H, Haji T, Matsuta N, Yamaguchi M, Hayashi T (2001) Characterization of morphological traits based on a genetic linkage map in peach. Breed Sci 51 :271—278 12 GENETIC DIVERSITY IN SWEET CHERRY GERMPLASM Background The cherry is one of the most important temperate fruit crops in the world. There are two types of cherries. Sweet cherry (Prunus avium L.), is eaten fresh and its wild forms (i.e. mazzards) are used as a timber source and sour cherry (Prunus cerasus L.) is mainly used in processed food products. 375,000 hectares (Ha) of sweet cherry (with 1,896,000 Metric tons (Mt) of fruit harvest) and 248,000 Ha of tart cherry (with 1,035,000 Mt of fruit harvest) are grown worldwide (FAO 2005). The cost of production for cherry is quite high and various breeding programs around the world are operating to produce improved cultivars (Iezzoni 2008). The breeding for improved cultivars is dependent upon the successful introgression of desired traits from the land races and wild relatives of cherry. Origin and geographical range Sweet and sour cherries were originated in Central Asia (Vavilov 1951) and slowly spread to parts of Europe. The natural range of cherries includes temperate regions of Europe and south eastern Russia (Hedrick et al. 1915). Today, sweet cherry is cultivated in more than 40 countries representing temperate to subtropical climates. However, sour cherry is less widely spread compared to sweet cherry, and mainly grown in Europe and USA. (Dirlewanger et al. 2007). 13 Genetic diversity The genetic diversity of sweet cherry is represented by wild forest cherries (i.e. mazzards), land races, cultivars, plant materials available from the crosses from the breeding programs, other related species (i.e. sour, ground and duke cherries) and other wild cherry species in family Rosaceae. Much of the genetic diversity is available from the wild forms and landraces from the center of origin. The introgression of these exotic germplasm to Pacific North West sweet cherry breeding is important to produce improved cultivars. However, understanding the genetic distance between exotic and Pacific North West sweet cherry gerrnplasms is important for successful introgression. Sweet cherry is strictly self-incompatible, which promotes 100% out breeding (de Nettancourt 2001), thus, very high genetic heterozygosity is expected within the germplasm. However, vegetative propagation through grafting has fixed heterozygosity within cultivars, limiting the chance events of increasing the diversity in orchards. The genetic diversity of sweet cherry has been examined for various objectives but none of the studies were aiming to find the genetic distance between Pacific North West and European sweet cherry cultivars (Brettin et a1. 2000; Dirlewanger, et al. 2002). The most studied area of the genetic diversity in sweet cherry is the diversity of S-alleles. Sonneveld et al. (2003), De Cuyper et al. (2005), Wunch and Hormaza (2004) and Vaughan et al. (2008) reported 31 S-alleles (S 1 -S7, 59-532) in sweet cherry. 14 Breeding Breeding is quite slow compared to other rosaceous fruit crops like apple and peach. The main breeding goals for sweet cherry is large fruit size, high fruit quality, short juvenile phase, self compatibility, rain cracking resistance and pest and disease resistance (Dirlewanger et al. 2007). Even though the classical breeding programs are slow, many cultivars have been made available to the growers and breeders to use them as parent materials. However, these cultivars are selections from the natural populations or just one generation away from the wild progenitors (Iezzoni et al. 1990). The long generation time, self incompatibility and small number of seeds per cross, make cherry breeding a difficult task. Recently, marker assisted breeding was introduced to address some of the difficulties in breeding but it is still in the developing phase. The most important accomplishment in sweet cherry breeding has been the introduction of self compatibility through mutational breeding (Lewis and Crowe 1954) and the ability to genotype cultivars for S-alleles by using DNA fingerprinting to select and grow sufficient number of polleniser-trees in the cherry orchards. 15 Chapter Two: Goal The aim of the Chapter Two was to assess the genetic diversity of Pacific North West sweet cherry germplasm in comparison to a set of European sweet cherry land races and a wild cherry selection which have not been introduced to the Pacific North West sweet cherry breeding. This study used allele data from 77 DNA markers, identified unique alleles and constructed graphical genotypes for all the Prunus avium selections used. The future marker assisted breeding programs and genetic diversity studies on Prunus will be immensely benefited from the findings of this study. 16 LITERATURE CITED Brettin TS, Karle R, Crowe EL, Iezzoni AF (2000) Chloroplast inheritance and DNA variation in sweet, sour and ground cherry. J Heredity 91 :75—79 De Cuyper B, Sonneveld T, Tobutt KR. 2005 Determining self-incompatibility genotypes in Belgian wild cherries. Mol Ecol 14:945—955 de Nettancourt D (2001) Incompatibility and incongruity in wild and cultivated plants, Springer, Berlin Dirlewanger E, Claverie, J, Wunsch A, Iezzoni AF (2007) Cherry. Genome Mapping and Molecular Breeding in Plants. Vol 4: fruits and nuts, Ed. Kole C, Springer p. 104—1 18 Dirlewanger E, Cosson P, Tavaud M, Aranzana J, Poizat C, Zanetto A, Arus P, Laigret F (2002) Development of microsatellite markers in peach [Prunus persica (L.) Batsch] and their use in genetic diversity analysis in peach and sweet cherry (Prunus avium L.). Theor Appl Genet 105:127—138 F A0 (2005) Food and Agricultural Organization of the United Nations. http://faostat.fao.org/site/336/default.aspx Hedrick UP (1915). The history of cultivated cherries. In: Hedrick UP, Howe GH, Taylor OM, Tubergen CB, Wellington R (eds) The Cherries of New York. JB Lyon company, State Printers, Albany, NY pp 3964 Iezzoni AF (2008) Cherries. Temperate Fruit Crop Breeding. Ed: Hancock J F, Springer p. 151—176 Iezzoni A, Schmidt H, Albertini A (1990) Cherries (Prunus spp), in Genetic resources of temperate fruit and nut crops. Eds. Moore JN, Ballington JR Jr, Int Soc Hortic Sci. Wageningen, The Netherlands p. 111—173 17 Lewis D, Crowe LK (1954) Structure of the incompatibility gene. IV Types of mutation in Prunus avium L. Heredity 8:357—363. Sonneveld T, Tobutt KR, Robbins TP (2003) Allele-specific PCR detection of sweet cherry self-incompatibility (S) alleles S] to S 16 using consensus and allele-specific primers. Theor Appl Genet 107:1059—1070 Vaughan SP, Boskovic RI, Gisbert-Climent A, Russell K, Tobutt KR (2008) Characterization of novel S-alleles from cherry (Prunus avium L.). Tree Genet Genomes 4:531—541 Vavilov NI (1951) The origin, variation, immunity and breeding of cultivated plants. Ronald, New York Wunsch A, Hormaza J I (2002) Molecular characterisation of sweet cherry (Prunus avium L.) genotypes using peach [Prunus persica (L.) Batsch] SSR sequences. Heredity 89:56—63. 18 CHAPTER ONE QTL ANALYSIS OF FRUIT SKIN AND FLESH COLOR IN SWEET CHERRY (Prunus avium L.) 19 INTRODUCTION Sweet cherry exhibits a continuous range of fruit skin and flesh colors from the dark mahogany color skinned and fleshed types, to those that have yellow skin with a red blush and yellow flesh. This variation in sweet cherry fruit skin and flesh color is used to classify different market types and to determine fruit maturity (Facteau et al. 1983). For example, dark mahogany cherries such as ‘Bing’ are favored in the majority of markets (Miller et al. 1986; Lyngstand and Sekse 1995; Wermund and F earne 2000; Crisosto et al. 2003, Turner et al. 2007); however, blushed skinned and yellow fleshed sweet cherries such as ‘Rainier’ are preferred in Asia. Despite the importance of fruit skin and flesh color in sweet cherry, the genetic control is not well understood. Fogle (1958) and Schmidt (1998) concluded that red skin color is dominant to yellow and proposed the presence of one major (A/a) and one minor gene (B/b) that exhibit epistasis. A/a was also suggested to control flesh color where A- and aa would confer mahogany and yellow flesh, respectively. The dominance of mahogany over yellow was supported by data from European breeding populations (Hedtrich 1985; Georgiev 1985; Rodrigues et al. 2008; and Tobutt and Boskovic 1996). However, collectively these studies also suggested that the genetic control of cherry skin and flesh color must involve additional minor genes to account for the wide range in color (from light yellow, pinks, reds, to dark mahogany). 2O To further investigate the genetic control of fruit skin and flesh color in cherry, an existing sweet cherry linkage mapping population that was segregating for these traits, and the available linkage map (Olmstead et al. 2008) were used for QTL analysis. The mapping population was a pseudo testcross between the blush and yellow fleshed Emperor Francis (EF) and dark mahogany skinned and fleshed New York 54 (NY). To facilitate a QTL approach, fruit color was quantified using L*, a* and b* color metrics where L* represents lightness, a* represents red/greenness, and b* represents blue/yellowness. This L*, a* and b* colorimetric system has been used to quantify color pigments in sweet cherries (Crisosto et al. 2003, Clayton and Biasi 2003, Usenik et al. 2005), other Prunus species (Gil et al. 2002, Kita et al. 2007) and many other plant samples to include apple (Espley et al. 2007), tomato (Sacks and Francis 2001), and wheat (Zhang et al. 2008). The objective of this study was to determine the genetic control of fruit skin and flesh color in sweet cherry utilizing a QTL approach. 21 MATERIALS AND METHODS Plant material The QTL analysis was based on a sweet cherry mapping population of 190 pseudo-testcross progeny individuals (~equal numbers from reciprocal crosses) from a cross between a landrace variety ‘Emperor Francis’ (EF), and a wild ‘mazzard’ sweet cherry ‘New York 54’ (NY). A subset of 94 progeny individuals from this population were grafted onto Giesla® 6, a semi-dwarfing precocious rootstock, to provide a clonal replicate. Both the original seedling population and the grafted subset were planted at the Michigan State University Clarksville Horticultural Research Station, Clarksville, Mich., USA. In 2006 and 2007 all the evaluations were from fruits fi'om the original seedlings. However, in 2008 a spring freeze killed the majority of the flowers on trees of the original population, and fruits were only evaluated from a subset of 94 individuals planted in a grafted plot that did not undergo freeze damage. This entire plot of 94 individuals was netted one week prior to fruit harvest to protect the ripening fruit from bird damage and an electric fence was installed around the perimeter of the plot to deter raccoons. Fruit sampling and evaluation Five fruits (one to four on the original seedlings if fewer fruit were available) were sampled from the trees. Fruit maturity was judged by observing the luster or dullness of the appearance of cherry fruit skin. However, because of the difficulty in judging maturity, each progeny individual was harvested multiple times, approximately 22 twice a week for a maximum of four harvest times. The data from the multiple harvests of each tree were compared using ANOVA to identify the maximum color potential to be used in QTL analysis. In all three years, color card readings were recorded from the darkest location of the fi'uit skin (skin color 1, SCI), lightest location (skin color 2, SC2) and flesh color (FC). Nine (0-8) and five (1-5) color card categories were used to qualitatively measure skin color and flesh color respectively (Table1.1 and Table 1.2). Color card categories for skin color were defined according to colors previously identified for the Sweet Cherry Maturity Index which was manufactured by Colorcurve Systems, Inc (, East Lansing, Mich.) and color chips from The Flower Council of Holland (FCH), Leiden, The Royal Horticultural Society (RHS), London. Color card categories for flesh color were defined according to Washington State University’s Sweet Cherry Flesh Color Index and The FCH Leiden, The RHS, London. SCI, SC2, and FC were quantitatively evaluated for lightness (L*), redness (a*), and yellowness (b*) using a spectrophotometer (CM-2002, Minolta, Tokyo, Japan). L* measures the range from black (lower values) to white (higher values), a* measures the range from red (higher values) to green (lower values), and b* measures the range from blue (lower values) to yellow (higher values). 23 Table 1.1: Description of the color card categories for fruit skin color in sweet cherry used for QTL analysis Correspondent Color card Color Color classification in RHS color category categorya description . Color Chartb m sweet cherry maturity index3 0 Translucent - White — 155 D 1 Pale yellow - Yellow — 10 A 2 Orange - Grayish orange — 170 D 3 Light red - Red — 39 A 4 Red 1 Grayish red — 179 A 5 Dark red 2 Grayish red — 181 A 6 Light mahogany 3 Grayish purple — 183 A 7 Mahogany 4 Grayish purple — 187 B 8 Dark Mahogany 5 Grayish purple— 187 A aSweet Cherry Maturity Index, Agricultural Engineering Department, Michigan State University, East Lansing, MI 48824. Manufactured by Colorcurve Systems, Inc. Color card categories 1-3 were not included as this Index was developed for dark colored cherries. bThe flower council of Holland, Leiden; The Royal Horticultural Society (RHS), London 24 Table 1.2: Description of the color card ratings for fruit flesh color in sweet cherry used in the QTL analysis Color card category in the Color description Color classification in RHS sweet cherry flesh color Color Chartb indexa 1 Clear to pale yellow Yellow — 11 A 2 Pale pink Red — 37 A 3 Red Grayish orange - 170 D 4 Mahogany Grayish red — 182 A 5 Dark mahogany Grayish purple — 187 A 3‘Washington State University’s Sweet Cherry Flesh Color Index bThe flower council of Holland, Leiden; The Royal Horticultural Society (RHS), London 25 Statistical analysis for color measurements The descriptive statistics of the color data were calculated using the Univariate procedure of SAS version 9.1 (SAS Institute 2006). The differences in color measurements between the two parents were compared using a t-test (P < 0.05). Pearson correlations for SCI, SC2, and PC using the color card data for 2006, 2007 and 2008 and the L* a* and b* data from 2008 were calculated using the CORR procedure of SAS version 9.1 (SAS Institute 2006). In 2008, estimates of broad-sense heritability were calculated from those seedlings for which measurements were taken from both the original seedling and the grafted replicate using an analysis of variance (ANOVA) Broad- sense heritability was estimated by using variance components with the formula, 2 2 2 2 2 . . . 2 . H =O'g / (O'g +6ng / 1‘), where 0'g IS the genetlc variance of progeny, 0'ng IS the interaction variance between progeny and plot, and r is the number of plots (i.e. seedling plot and grafted replicate). QTL analysis A consensus map of the two individual maps, NY and EF (Olmstead et al. 2008) was used for the QTL analysis. The consensus linkage map has a total of 197 markers, including 102 simple sequence repeat (SSR) markers, 61 amplified fragment length polymorphism (AFLP) markers, 27 gene-derived markers, and 7 sequence related amplified polymorphism (SRAP) markers. QTL analysis was done using MapQTL 5.0 (Van Ooijen 2004). Kruskal Wallis nonparametric test, interval mapping (IM), and multiple QTL mapping (MQM) were performed for each trait. In MQM, the markers closest to the peak of the QTL detected by IM were used as cofactors. The LOD 26 thresholds were estimated with 1,000 permutation tests for each trait. The QTLs with LOD values higher than the genome wide threshold at P < 0.05 were considered most significant, but QTLs with LOD values higher than genome wide threshold at P < 0.1 and QTLs with LOD values higher than individual linkage group level at P < 0.05 were also reported. QTLs with differing thresholds were reported as the use of phenotypic data that are not normally distributed, can result in unusually high LOD thresholds (Li et al. 2006 and Buil et al. 2005) leading to some real QTLs undetected. The linkage maps and QTL positions were drawn using MapChart (Voorrips 2002). 27 RESULTS AND DISCUSSION Color data Color card readings for SCI, SC2, and FC from the individuals in the linkage mapping population were significantly correlated across all three years (P < 0.0001) (Table 1.3) indicating that there was minimal inter-year variation in color. For 2008, the color card, L*, a* and b* values from the 94 seedlings in the clonally replicated mapping population subset were all significantly correlated for both skin (SCI and SC2) and flesh color (FC) (P < 0.0001; Table 1.4). In particular, color card readings for SCI, SC2, and FC exhibited strong significant negative correlations to L* and b*. This reflects increases in darkness (- L*) and increases in blueness (- b*) in the dark mahogany fruit types. The significant correlations across the three fruit measurements suggest that there is a common genetic mechanism controlling skin and flesh color. For skin color (SCI and SC2), a* was negatively correlated with the color card data; however, for PC, a* and the card color data were positively correlated. This suggests that a different genetic mechanism may contribute to the variation in a* in the skin versus the flesh. EF and NY exhibited significantly different color values for all traits except for SC2 a* (Table 1.5). This similarity between the two parents for a* reflects the fact that redness is not so important in lighter side (non blush or yellow) of EF. Collectively these 28 results indicate that the red — green vector (a*) alone, does not adequately describe the quantitative variation in the cherry fruit and skin color. 29 Table 1.3: Pearson’s correlation coefficients for skin color 1 (SCI), skin color 2 (SC2), and flesh color (FC) card readings from the NY X EF progeny in 2006, 2007 and 2008 Trait 2006 vs. 2007 2006 vs. 2008 2007 vs. 2008 3C1 0.80a(138)b 0.78 (85) 0.84 (89) SC2 0.77 (138) 0.79 (85) 0.85 (89) FC 0.88 (138) 0.82 (80) 0.91 (85) aall the values are significant at P < 0.0001 b . . . . . The number of 1nd1v1duals in each comparison. 30 Table 1.4: Pearson’s correlation coefficients for skin color 1 (SCI), skin color 2 (SC2) and flesh color (F C) card and L*, a*, and b* values for NY >< EF progeny evaluated in 2008 = a “a == a a z 8 8 a g 8 8 9. g a a 8 0.87K SCI card -0.90 -0.90 0.95 -0.84 -0.63 -0.91 0.88 -0.84 0.49 -0.86 SCI L* 0.90 0.97 -0.84 0.86 0.49 0.88 -0.73 0.72 -0.34 0.80 SCI a* 0.96 -0.90 0.86 0.70 0.92 -0.86 0.82 -0.36 0.88 SCI b* -0.89 0.88 0.56 0.92 -0.79 0.78 -0.37 0.85 SC2 card 088 -0.63 -0.93 0.90 -0.85 0.49 -0.88 SC2 L* 0.44 0.94 -0.76 0.76 -0.38 0.81 SC2 a* 0.61 -0.77 0.68 -0.34 0.70 SC2 h* -0.86 0.83 -0.43 0.90 FC card 087 0.53 089 PC L* -0.48 0.89 FC a* -0.37 xAll the values are significant at P < 0.0001. Each comparison represents 1861 to 1865 individual fruits 31 Table 1.5: Means and standard deviations for skin color 1 (SCI), skin color 2 (SC2), and flesh color (FC) values for EF and NY in 2008 Tissue Traitz EFy NY SCl 8.0 b (0.0) Card 3.5 a (0.9) L* 47.4 a (5.1) 27.3 b (0.9) a* 35.4 a (2.9) 7.0 b (2.8) b* 21.7 a (3.0) 0.6 b (0.6) SC2 Card 1.3 a (0.5) 7.8 b (0.4) L* 69.1 a (6.0) 27.7 b (1.1) a* 7.0 a (10.3) 9.0 a (4.0) b* 35.3 a(5.7) 1.3b(1.1) FC Card 1.0 a (0.0) 4.8 b (0.4) L* 40.8 a (5.5) 20.7 b (2.6) a"‘ 3.8 a (1.6) 9.7 b (3.7) b* 26.7 a (1.9) 2.6 b (1.6) y Means denoted by same letters in the same row are not significantly different at P < 0.0001. ZUnits: card (color card categories), L*, a* and b* (colorimeter reading) 32 Color development In 2008, the pattern of skin and flesh color development for the parents and progeny were evaluated over four harvest dates to identify the colorimetric values that best represented the maximum color potential of each individual. The skin color metrics for dark mahogany fruits and flesh color metrics of all the fruits exhibited little differences across all four harvest dates (Table 1.6). However, for EF, the majority of the skin color values were significantly different among the four harvest dates. The changes in the EF skin measurements indicated that the fi'uit skin was becoming less yellow and this change was accompanied by a significant increase in the red blush on the fruit by the last harvest date. However, the flesh color of EF did not exhibit a parallel increase in red pigmentation. Instead, the EF flesh color remained yellow highlighting the importance of carotenoid pigments in the EF blush type cherries compared to the anthocyanin pigments in the red fleshed cherries. Due to the different final colors between the blush and mahogany cherry types, the progression of color development across harvest date was evaluated using separate groups of seedlings that represented these two color classes. The overall trend was for decreases in L*, a* and b* and increases in card values over time (Table 1.6) that represented a darkening of the fruit skin and flesh. The minimum L*, a* and b* and maximum card values for each seedling were used in the QTL analysis as it represented the maximum color maturity for each seedling. 33 Table 1.6: The progression of fruit skin and flesh color over harvest data for blush and mahogany classes of NY54 x EF progeny for year 2008 . S # Fruit color class Location COM" metric June 20 June 23 June 26 June 30 Blush SCl Card 4.75 a 5.0 b 5.4 c 5.3 c L* 37.3 a 35.1 b 33.8 c 33.5 c a* 28.4 a 26.1 b 24.2 c 21.7 d b* 13.2 a 10.8 b 9.8 c 8.4 d Mahogany SCI Card 7.8 a 7.9 b 7.9 b 7.9 b L* 29.2 a 28.7 b 28.0 c 28.4 c a* 12.6 a 9.6 b 7.3 c 5.7 d b* 2.0 a 1.3 b 0.9 c 0.6 d Blush SC2 Card 3.03 a 3.8 b 3.8 b 4.1 c L* 47.5 a 43.6 b 42.9 b 41.2 c a“ 22.5 a 24.8 b 23.0 c 23.5 c b* 20.1 a 18.0b 16.9b 15.1 c Mahogany SC2 Card 7.6 a 7.8 b 7.7 b 7.8 b L* 29.5 a 29.2 a 28.5 b 29.0 b a* 14.1a ll.4b 9.2c 8.1d b* 2.9a I.8b l.8b 1.5b Blush PC Card 1.5 a 1.1 b 1.1 b 1.2 b L* 33.4 a 35.8 a 35.7 a 35.8 a a* 4.3 a 3.4 b 4.4 c 4.4 c b* l7.3a 15.1 b 16.5c 15.4d Mahogany FC Card 4.2 a 4.4 b 4.5 b 4.4 b L"‘ 21.8a 2I.Ia 21.4a 21.6a a* 11.7 a 8.0 b 7.8 b 8.6 c b* 4.6 a 2.4 b 3.6 c 3.7 c sMeans followed by different letters within the same row are significantly different at P < 0.05 across the rows. The least square (LS) means are shown here (calculated from General Linear Model Procedure) #Harvest days for 2008 fruiting season, growing degree days calculated from January 1, 2008 with a base temperature of 4.4 C (June 20: 723.2, June 23: 763.8, June 26: 811.3 and June 30: 872.9) and SUnits: card (color card categories), L*, a* and b* 34 Data distribution The pattern of the data distribution was examined for the minimum L*, a* and b* and maximum card values of all the individuals for 2008 data. The progeny values for all the color traits were not normally distributed (Figure 1.1) and the Kolmogorov-Smimov Normality Coefficients (KS) were all significant (P < 0.01) (Table 1.7). In addition, the color card and F C L* and b* distributions in particular suggested a 9:7 ratio characteristic of a two locus interaction. These skewed distributions were consistent with the suggestion of Fogle (195 8) and Schmidt (1998) that there is at least one major gene controlling the genetic variation in fruit color and possible epistasis. Transgressive segregants were identified for SC2 a* and F C a* whereas for all the other color traits, the progeny had phenotypic values intermediate to the parents. For SC2 a* and F C a* there was an abundance of progeny individuals that had redness values above that of the red fi'uited NY parent. The transgressive segregants identified for SC2 and F C a* were consistent with the correlation results that suggested a* in the skin and flesh is under different genetic control than the color measured by the color card, L* and b*. Broad sense heritability estimates (H2) for all the traits except SC2 a* were higher than 0.80 (Table 1.7). This suggests that the intensity of the red blush on the skin of the light colored cherries may be more sensitive to environmental conditions than the overall skin and flesh color. In particular, the intensity of the red blush is was reduced on fruit from the original seedling block, possibly due to less light interception and slightly immature fruit, compared to the fruit harvested from the clonal orchard where the netting permitted us to harvest fruits at optimum maturity. 35 Figure 1.1: A-L Progeny frequency distribution of color traits measured in 2008 (A) SC1 card. (B) SC2 card. (C) FC card. (D) SCI L*. (E) SC2 L*, (F) F C L*, (G) SCI a*. (H) SC2 a*. (1) PC a*. (J) SC 1 b*. (K) SC2 b*. (L) FC b*. EF and NY parental values are shown. 36 Fig 1.1 Cont. A: Skin Color 1 Card B: Skin Color 2 Card 1,50, , *--NY54 a l 5401 .2 3307 “5 l .20) 201..- ._..m, .- 4 5 1 2 3 6 7 8 Color card category C: Flesh Color Card Number of Individua S 8 o l l 3 Color card category 37 Fig 1.1 Cont. D:3SOkin Color 1 Lightness (L*) a a 5 .2 £20 -. 7777777777777777777777777 a l “a ‘ NY54 EF 1.. L ., E10 2 0.1:: II: lllIl , ‘ . ,m ‘ 18 20 22 24 26 28 30 32 34 36 38 40 41 Lightness (L*) E: Skin Color 2 Lightness (L*) “30‘ E f NY54 E 1 £20 1 5 1 g . 5103 , , 7 g 1 l 1 z 0 111...“, III] II“ llllll llllll “H .11, .. -Jl. 15 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 Lightness (L*) F: Flesh Color Lightness (L*) 30..., .2 5 IE ~520er E NY54 ’5 . EF 5- 1 .810» E .1 ” 2 II II 0111.11,.11111 8,II.1;.51.:.mflll II“... 14 16 20 22 26 28 32 35 38 8Lightness (L*) 38 Fig 1.1 Cont. G. azfikin Color 1 Redness (a*) I , , , , :Oil EF III:..1.I.J.IIIIIII,.I.L. 1 15 17 19 21 23 25 27 29 1Redness (a*) _ n—- o M (I! Number of Individuals H: Skin Color 2 Redness (a*) N O NY54 l 151 I Number of Individuals Illlalll II 1 1. I l I l -5 -11357911131517 23 Redness(a*) I: Flesh Color Redness (a*) 25 l NY54 N O p—o M —. O ‘_._l 1 A 24. Number of Individuals LII F1 1:1 ‘ll 1""; .~ 5‘1: , 1:1, ‘ 5 ’2‘» LI! ’1’ T' '7” 'I" ' 'T '1 0 1 2 3 4 5 6 7 8 9 10 11 Redness (a*) O 39 Fig 1.1 Cont. J: ggin Color 1 Yellowness (b*) ‘ NY54 A O N O i l l 0 . I-I.n.m.lfil.n.fllllll.fl..._fln,fll.n-._nfl,n,i , ,2-..-, ., 0 2 4 6 8101214161820212325272931 Yellowness (b*) Number of Individuals 0 K: Skin Color 2 Yellowness (b*) £1 NY54 3 £40 .2 E301 h-I 320 - .8 EF 5101 w . _ . J1 0.1rmlfllurmm, ,II.. 012 3 4 5 6 7 8 91011121314151617181920 Yellowness (b*) L: Flesh Color Yellowness (b*) 50,1 ,. 5 £ a E40 NY54 .2 '6 E. '0- O E ,. EF 5 - + I -1012 3 5 7 8 9101112131415161718 Yellowness(b*) 40 Table 1.7: Summary statistics and heritability of color data for year 2008 Broad Mean Kolmogorov-Smirnov Color 3 3 Tissue (Standard sense Minimum Maximum Normality Coefficient metric . . . h Deviation) "'mb'my (KS)*** 2 (H ) SCI Card 6.6 (1.5) 0.96 2.0 8.0 0.1 L"I 31.4 (4.2) 0.82 17.9 54.1 0.2 a“ 15.9 (9.9) 0.95 0.7 42.3 0.1 b* 5.5 (5.7) 0.90 -0.5 34.3 0.2 SC2 Card 5.8 (2.2) 0.95 1.0 8.0 0.2 L” 36.0 (9.4) 0.89 15.0 99.2 0.2 a" 16.4 (9.1) 0.74 -5.1 38.1 0.1 b* 9.2 (8.9) 0.96 -0.4 45.9 0.2 PC Card 2.8 (1.8) 0.98 1.0 5.0 0.2 L“ 28.6 (8.3) 0.94 3.6 61.9 0.1 3* 6.7 (3.9) 0.86 -0.5 22.3 0.1 b* 9.7 (7.1) 0.96 -0.9 30.9 0.1 $Units: card (color card categories), L* (lightness), a* (red/greenness) and b* (yellow/blueness) (colorimeter readings) *** KS is significant at P < 0.01. Significant KS indicates the deviation from normality. 41 QTL analysis For 2008 color card and L*, a* and b* data, significant QTLs detected for SC] card, SCI a*, SC2 card, SC2 b*, FC card, FC L* and FC b* on linkage group (LG) 3 at 53.7 cM and the average variability (R2) explained by these QTLs was 87.2% and ranged from 78.4 % for SC2 b* to 94.7% for FC L* and F C b* (Table 1.8, Figure 1.2A) indicating that there is a major QTL on LG3 at 53.7 cM for anthocyanin pigmentation. Significant QTLs for five other color metrics were also located on LG3, however the predicted peak positions ranged from 12.8 cM for PC a* to 40.8 for SC2 a*. The average R2 for these QTLs was 25.6% and ranged from 13.5% for SC2 L* to 44% for PC a* (Table 1.8, Figure 1.2A). This suggests that there is at least one additional color QTL located on LG3. To test whether the major QTL on LG3 was significant in 2006 and 2007, QTL analysis was done for these two years using the color card data for SC], SC2 and FC and (Figure 1.3). Significant QTLs detected for SCI card, SC2 card and FC card for 2006 and 2007 data on linkage group (LG) 3 at 53.7 cM as in 2008 data. The average R2 for these color card QTLs were 85.6% and ranged from 73.8% for 2007 SC2 card and 93.8% for 2007 PC card. The identification of a QTL on LG3 at 53.7 cM for two additional years validated our finding that there is a major fruit color QTL on that genomic location. For the 2008 color card and L*, a* and b* data, three more significant color QTLs were identified, one for SCI b* and two for F C a*. For SC 1 b*, a QTL was detected on 42 LG6 with an R2 of 42.8% (Table 1.8, Figure 1.2C). For FC a*, two additional QTLs were detected on LG5 and LG8 (Table 1.8, Figures 1.2 B and D). The QTL on LG5 and LG8 explained 18.7% and 44.0% of the phenotypic variation, respectively. The identification of additional QTLs for FC a* is consistent with phenotypic data that suggested PC a* reflected a different color pattern compared to the other color metrics. 43 Table 1.8: QTLs for color card values, L*, a* and b* for SCI, SC2 and FC identified in the NY X EF F1 population in 2008 data QTL Peak position (closest 118:1: :2:ng ggfigge marker and T x E bin map LOD R2b posrtlona) SCI Card 3 53.7 (PR41, 3:37) 13.3* 87.3 L* 3 21.0 (UDP97-403, 3:12) 4.87”” 21.2 3* 3 53.7 (PR41, 3237) 7.9* 80.0 b* 3 21.0 (UDP97-403 3:12) 60*" 26.0 b* 6 15.0 (UDP96-001 ~6Z25) 4.1"I 42.8 SC2 Card 3 53.7 (PR41, 3:37) 135* 87.5 L* 3 21.0 (UDP97-403 3212) 3.0* 13.5 8* 3 40.8 (UDP98-416) 3.9”“ 23.3 13* 3 53.7 (PR41, 3237) 7.7** 78.4 FC Card 3 53.7 (PR41, 3237) 28.1* 94.7 L"K 3 53.7 (PR41, 3237) 11.2* 86.2 a* 3 12.8 (EAC-MCTA-360) 35* 20.8 3* 5 27.8 (EAT-MCCC-285 ~5221) 3.2* 18.7 3* 8 83.3 (PSIH3 — unknown) 4.5'” 44.0 I)" 3 53.7 (PR41, 3237) 13.7* 87.9 aQTL peak position is expressed in cM and the closest marker and T X E bin map position is indicated in bracket. QTLs were estimated using multiple QTL mapping (MQM) method of MapQTL 5.0 sz, percentage of phenotypic variation explained by the QTL *** The LOD value significant at P < 0.05 based on 1000 genome wide permutation tests ** The LOD value significant at P < 0.1 based on 1000 genome wide permutation tests * The LOD value significant at P <0.05 based on 1000 individual linkage group wide permutation tests 44 Figure 1.2: A-D Locations of QTLs for color card and L*, a* and b* values for SCI (darkest location of the fruit skin), SC2 (lightest location of the fruit skin) and FC (flesh color) using the multiple QTL mapping method. The variability explained by QTL (R2%) is shown after the trait name of each QTL. l-LOD and 2-LOD support intervals of each QTL are marked by thick and thin bars, respectively. Blank bars represent QTLs for color card QTLs. Black bars represent QTLs for L*. Bars filled with one sided hatch lines represent QTLs for a*. Bars filled with two sided hatch lines represent QTLs for b*. Only linkage groups including the QTLs are presented. (A) Linkage group 3, (B) Linkage group 5, (C) Linkage group 6, (D) Linkage group 8. LOD scores and the percentage variability explained by the QTLs (R2) are presented in the Table 1.8 45 Fig 1.2 Cont. A L G3 / EPPCU5090 I—q AMPAIOI T\ MA034 / UDAp-429 :, MA066a EAC-MCTA-98 UDP97-403 \ EAC-MCTA-l65 ‘\ PMS30 ‘\ BPPCT039 ‘\ EAC-MCTA-79 :~ EPDCU3083 \ UDP98-416 :\ EMPaS12 \ CPDCT037 ~~ EPPB4221-PR41 2. Ma039a IQ EAA-MCTT-525 PR1 10 73.3 79.3 \ 80.8 / EAT-MCTC-SSO _/ EMPA014 _\ EMPaS02 89.4 N U, EAT-MCCC-350 Q‘ EPPCU9994-PR74 [:1-I 9133138 fl-I lHOS r[IDS 46 1:1-1 P193138 (HOS L I "[238 ; \ \ \ \521 \n \ra \ \ 8 \ \ \ \ \ \ \ §m \S \19 N \ I-rj l 69 69 if; 8: =- 2 F ‘7 Fig 1.2 Cont. B LG5 0.0 7.7 12.8 20.7 IIIIII I 75.5 1 1 t / \ \ (ITlll 8 EPPCU096 1 EPPCU9168 MEI-EM1-850 BPPCT026 EAT-MCCC-278 UDP96-0 19 EPPCU0863-PR84 BPPCT037 EMPaS 1 1 EAA-MCAC-440 CPDCT028 PR90 EAA-MCAC-340 EPDCU5 1 83 PR26 EPPB42 1 6-PR5 1 EPPB4230 CPDCT022 BPPCT014 47 9331 Fig 1.2 Cont. LG6 0.0 PR85 4.0 EPPCU3855-PR72 9.5 MEI-EM2-575 1 1.9 EMPaSOl 16.5 UDP96-001 19.2 EAT-MCTC-375 25.3 \g/ BPPCT008 28.3 Ma014a 31.9 — PR127 33.3 \ / EAA-MCCC-I60 35.7 e/ EAC-MCTA-225 37.8 \r/ CPPCT029 37.9 \—/ UDA-47l 39.6 \—/ nBPPCT006 40.3 \:/ EMPA004 43.0 \ / CPSCT029 44.7 \P/ EAT-MCTC-272 449 /=\ BPPCT009 48.5 \ / CPPCT023 50.1 \:/ EgggU2828 EPPCU3090 ——I Ill 1111 ll] EAA-MCAC-420 EAA-MCCC-I30 UDAp-4 1 3 ‘/ EAT-MCCC-IOO / UDP98-021 \ EPPB4227 / MaO40a PrPFT / PR93 EPPCU4092-PR56 / EAC-MCTA-350 / EAT-MCTC-I42 \ EAC-MCTA-185 82.4 CI 18:: PR121 48 QIDS Fig 1.2 Cont. D LG8 EAA-MCAA-398 4.3 \_/ EAA-MCCT-280 pchgms49 8:5 /"‘\ EAA-MCCT-225 EAA-MCCC-l 32 EPPCU4726 33.4 \r = EAA-MCCT-410 / CPPCT006 PR25/22 \ EPDCU3516 33.7 /—~ 34.6 / \ EAA-MCAA-322 4; .U‘ / l 4:. \0 be I ll Ur 1.» \O \[ I / EAA-MCAC-258 / MA023a :/ EAT-MCTC-425 _/ EAA-MCTT-315 __\ EAT-MCTC-188 EAA-MCCC-425 \ EAT-MCTC-3l2 EAT-MCTC-330 EAT-MCTC-315 PR27 MEI-EM2-475 78.3 PSIH3 87.3 104.1 EAA-MCCT-345 111.3 EAT-MCTC-S 10 121.9 MEI-EM2-570 49 \ EAA-MCAC-430 MD201 a 93d Figure 1.3: Locations of QTLs on LG3 for color card data of 2006, 2007 and 2008 for SCI (darkest location of the fruit skin), SC2 (lightest location of the fruit skin) and FC (flesh color) using the multiple QTL mapping method. Blank bars represent QTLs. 1- LOD and 2-LOD support intervals of each QTL are marked by thick and thin bars, respectively. The percentage variability explained by the QTL (R2) and the level of QTL significance in number of stars (***: LOD value significant at P < 0.05 genome wide, **: LOD value significant at P < 0.1 genome wide, * : The LOD value significant at P <0.05 individual linkage group wide, based on 1000 permutation tests) are shown with the QTLs. 50 LG3 0.0 wo~ EPPCU9994-PR74 6,7 \_/ EPPCU5090 AMPAIOl _\ MA034 18.9 \ / UDAp-429 MA066a EAC-MCTA-98 UDP97-403 _\ EAC-MCTA-165 29.9 /_\ PMS30 _\ BPPCT039 _\ EAC-MCTA-79 EPDCU3083 /'l\ UDP98-416 44.0 /2\ EMPas12 \ CPDCT037 50.7 ’T\ EPPB4221-PR41 MaO39a /C\ EAA-MCTT-SZS / \ PR110 EAT-MCTC-550 73.3 79.3 \ 80.8 / _/ EMPA014 "\ EMPaSOZ 89.4 N U/ EAT-MCCC-350 N N “N §as§383§§ \reoo sesamsgga infinmwinOE NO geez-sgann o 99”” mflawfifi-j-r-r aaaaaaere go \000 \O E’opafidPHN-fl seriouboPOPPS J**~O*J****** gei- ** 51 QTL haplotypes To further investigate the allele effects of the color QTLs, the progeny individuals were sorted by their parental QTL haplotypes that were defined by the allelic states of at least two linked markers (Table 1.9). The choice of the two markers to represent the QTL haplotype was based on the fact that they should flank the QTL and at least one marker should be heterozygous in one parent. For example, the NY and EF QTL haplotypes for the QTL on LG 3 at 53.7 cM were defined by the alleles for AFLP marker, EAC-MCTA- 79 and SSR, MaO39a located at 35.6 cM and 54.2 cM, respectively. EAC-MCTA-79 is heterozygous in NY and homozygous in EF. To facilitate the genetic notation, other allele (i.e. cannot see in the gel and can be considered as a null allele) was designated as ‘$$’ following the format used for FlerTL (Bink et al. 2008), a sofiware used in pedigree based QTL analysis using multiple populations. Only EF is heterozygous for MaO39a. For the two QTLs on LG3 and LG6, there were four parental QTL haplotypes (a, b, c and d) as each parent was heterozygous for haplotypes. However, for LG5 and LG8 there were three parental QTL haplotypes as NY was homozygous for the LG5 QTL haplotype and EF was homozygous for the LG8 haplotype. The progeny color trait means were then calculated for each of the QTL haplotypes. For example, for the QTL on LG3 at 53.7 cM, four progeny classes were defined as “ac”, “ad”, “be”, and “bd” and the trait means were calculated from 29, 23, 23, and 14 progeny individuals, respectively (Table 1.10). Those progeny individuals that 52 received the LG3 “a” haplotype from NY had intensified color, most notably it increased darkness (card) and reduced redness (a*) in SCI, increased darkness (card) and increased blueness (b*) in SC2 and increased darkness (card and L*) and increased blueness (b*) in FC as many of the fruits were approaching mahogany color in both skin and flesh. The lighter colored fruit had the LG3 “b” haplotype from NY. As NY has dark mahogany skin and flesh, this finding for the major QTL on LG3, supports the prior observation that mahogany fruit (skin and flesh) is dominant to yellow fi'uit. Both EF and NY were heterozygous for the SC] L*, SCI b*, SC2 L*, SC2a* and PC a* QTL haplotypes on LG3 at ~21.0 cM (Table 1.11). Those progeny received “a” haplotype from NY had increased darkness (L*) and increased blueness (b*) in SCI and increased lightness (L*) and reduced redness (a*) in SC2. But the same haplotype “a” increased the redness (a*) in PC suggesting that flesh color is under different genetic control. Both EF and NY were also heterozygous for the SCI b* QTL haplotype on LG6 (Table 1.12). Those progeny that received the “d” haplotype from EF had a reduced b* value (increased blueness) compared to those that received the “c” haplotype. However, this effect was only present for those individuals that had the “b” haplotype from NY, not the “a” haplotype. This suggests that the QTL alleles on LG6 may interact. For the FC a* QTLs on LG5 and LG8 only one of the parents was heterozygous. NY was homozygous for the PC a* QTL haplotype on LG5 (Table 1.13). Therefore the 53 6‘ 9, trait means were calculated from those progeny individuals that received either the c or “d” haplotypes from EF. Those progeny individuals that received the “c” haplotype from EF had increased redness compared to those progeny that received the “d” haplotype. EF was homozygous for the PC a* QTL haplotype on LG8 (Table 1.14). Therefore the trait means were calculated from those progeny individuals that received either the “a” or “b” haplotype from NY. The presence of the “a” haplotype as opposed to the “b” haplotype was associated with an increase in red color. 54 Table 1.9: Definitions of parental haplotypes for five QTL regions on linkage groups 3, 5, 6 and 8 Linkage group Parent Haplotype Molecular marker EAC-MCTA-79 MaO39a NY a 79" 170 3 at 53.7 cM b my 170 EF c $$ 220 d $$ 170 MA066a BPPCT039a NY a 149 138 3 at ~21.0 cM b 142 133 EF c 142 145 d 142 138 BPPCT026 UDP96-019 NY a 164 202 5 EF c 164 205 d 170 202 EMPaSOl UDP96-001 NY a 228 129 6 b 222 131 EF 0 228 129 d 232 115 MD201a PS1H3 NY a 250 280 8 b 230 270 EF 0 230 270 xAllele fragment size in bp y$$z Confirmed null allele for marker, EAC-MCTA-79 55 Table 1.10: Card and a* of skin color 1 (SCI), Card and b* of skin color 2 (SC2) and Card, L8 and b* of flesh color (F C) of different genotype classes for the major QTL on linkage group 3 at 53.7 cM. Numbers in parenthesis are the number of progeny individuals . b Color Metric Halo e p typ a SCI SC2 FC Combination Card a* Card b* Card L* b* ac(29) 7.3a 8.2a 6.8a 4.0a 3.5a 21.0a 4.5a ad(23) 7.3a 7.2a 6.9a 3.0a 3.7a 21.2a 3.7a be (23) 6.2 b 15.0 b 5.2 b 9.8 b 2.1 b 27.8 b 9.9 b bd(14) 6.7b 13.6 b 6.0 b 6.8 b 2.3 b 25.7 b 8.9 b Means denoted by the same letters within column are not significantly different at P < 0.05 (done using Least Squares Means, General Linear Model SAS 9.1) aa, b, c, and d are the haplotypes as defined in Table 1.9 bUnits: card (color card categories), L*, a* and b* (colorimeter reading) 56 Table 1.11: L* and b* of skin color 1 (SCI), L* and a* of skin color 2 (SC2) and a* of flesh color (FC) of different genotype classes for the minor QTL on linkage group 3 at ~21.0 cM. Numbers in parenthesis are the number of progeny individuals Color Metricb Haplotype a SCl SC2 F C Combination L* b* L* a* a* ac (14) 27.3 a 0.3 a 26.4 a 4.7 a 4.4 a ad (32) 28.7 a 2.9 b 31.4 b 7.2 b 3.6 a be (13) 30.4 a 4.8 b 32.1 b 9.2 b 2.4 b bd (09) 29.9 a 3.9 b 32.2 b 14.2 b 1.6 b Means denoted by the same letters within column are not significantly different at P < 0.05 (done using Least Squares Means, General Linear Model SAS 9.1) aa, b, c, and d are the haplotypes as defined in Table 1.9 b . . . . Unrts: card (color card categorres), L*, a* and b* (colorrmeter readlng) 57 Table 1.12: b* of skin color 1 (SCI) of different genotype classes for the QTL region on linkage group 6. Numbers in brackets are the number of progeny individuals Color Metricb Haplotype SCl Combinationa b* ac (20) 2.7 a ad (30) 3.1 a be (18) 3.2 a bd (18) 2.2 a Means denoted by the same letters within column are not significantly different at P < 0.05 (done using Least Squares Means, General Linear Model SAS 9.1) aa, b, c, and d are the haplotypes as defined in Table 1.7 bUnits: card (color card categories), L*, a* and b* (colorimeter reading) 58 Table 1.13: a* of flesh color (F C) of different genotype classes for the QTL region on linkage group 5. Numbers in brackets are the number of progeny individuals Color Metricb Haplotype FC Combinationa 3* ac (33) 3.7 a ad (38) 2.8 a Means denoted by the same letters within column are not significantly different at P < 0.05 (done using Least Squares Means, General Linear Model SAS 9.1) 21a, c, and d are the haplotypes as defined in Table 1.7 bUnits: card (color card categories), L*, a* and b* (colorimeter reading) 59 Table 1.14: a* of flesh color (F C) of different genotype classes for the QTL region on linkage group 8. Numbers in brackets are the number of progeny individuals Color MetricF Haplotype a F C Combination 3* ac (31) 3.0 a bc (33) 3.5 a Means denoted by the same letters within column are not significantly different at P < 0.05 (done using Least Squares Means, General Linear Model SAS 9.1) ‘1a, b, c, and d are the haplotypes as defined in Table 1.7 bUnits: card (color card categories), L*, a* and b* (colorimeter reading) 60 Epistasis The bimodal pattern of some of the progeny distributions suggested the possibility of epistasis. To investigate this further, the major QTL on LG3 at 53.7 cM was considered as the major factor and the QTLs on LG3 at ~21.0 cM, LGs 5, 6 and 8 were considered separately as the second factor. The trait values for the different allelic states were determined using markers from the QTL peak positions. The mean SCI L* and SC2 L* values for genotypic classes defined by PR41 (the marker selected to represent major QTL on LG3) and Ma066a (the marker selected to represent minor QTL on LG3) were not different indicating there is no epistatic interaction for SCl L* and SC2 L*. The mean SCI b* values for PR41 genotypes when Ma066a was homozygous were greater than the mean SCI b* values for PR41 genotypes when Ma066a was heterozygous. This indicates the epistatic interaction for SCI b* between major and minor QTLs on LG3. The mean SC2 a* was highest for those progeny individuals that were heterozygous for PR41 and Ma066a and lowest for those progeny individuals that werehomozygous for PR 41 and heterozygous for Ma066a. This suggests a possible epistatic interaction for SC2 a* between major and minor QTLs on LG3. The mean FC a* values for PR41 genotypes when Ma066a was heterozygous were greater than the mean PC a* values for PR41 genotypes when Ma066a was homozygous. This indicates the epistatic interaction for SC 1 b* between major and minor QTLs on LG3 (Figure 1.4). 61 The mean F C a* values for those progeny individuals that were heterozygous for PR41 (a marker near the LG3 QTL peak) were similar, irrespectively of differences in the QTL allelic states for LG8 and LG5. However, for those progeny that were homozygous for PR41, the allelic states for PS1H3 (LG8 PC a* QTL) and BPPCT026 (LG5 PC a* QTL) did result in different color outcomes. This suggests that there may be an epistatic interaction between the QTL(s) on LG3 and the QTLs on LG5 and LG8. In contrast, for the LG6 SC 1 b* QTL, a maximum trait value was obtained for those progeny that had the 131 and 129 bp alleles for UDP96-001, irrespective of the allelic state at the PR41 locus (Figure 1.5). 62 Figure 1.4: A-E. The two-way inter genomic region interactions between the major QTL and the minor QTL regions on LG3 (A) Inter loci interaction for SC] L* between PR41 and Ma066a (B) Inter loci interaction for SC] b* between PR41 and Ma066a (C) Inter loci interaction for SC2 L“ between PR41 and Ma066a (D) Inter loci interaction for SC2 a* between PR41 and Ma066a (E) Inter loci interaction for FC a* between PR41 and Ma066a. Means denoted by same letter within each graph are not significantly different at P < 0.05 (done using Least Squares Means, General Linear Model SAS 9.1). Units: L*, a* and b* (colorimeter reading) 63 Fig 1.4 Cont. A 32.0 SCl L* 16.0 5 0.0 LGO3: PR41 ; 1 LGO3: Ma066a; 5.0 T SCl b* 2.5 ' 304" 29.83 a .__ 4 . 337/337 337/312 337/337 337/312 1 1 142/142 142/149 1‘ Allele/fragement (bp) 111—1 0.0 LGO3: PR41; LGO3: Ma066a; 337/337l337/312 337/337‘ 337/312 142/142 142/149 Allele/fragment (bp) 64 Fig 1.4 Cont. a 33.9 C 34-0 7 28.2 a SC2 L* 1 1 17.0 1 1 0.0 1 ‘7 1 fi—V “1 LGO3zPR41; 337/337 1 337/337 1 337/312 ; LGO3: Ma066a: 142/142 1 142/149 Allele/fragme nt (bp) D 14.0 ~ SC2 a* 1 a 1 8.2 7.0 '1 5.4C 0.0 , — ~ 1 - 1 LGO3: PR41;1 337/337 i LGO3: Ma066a; 1 337/312 1 337/337 1 337/312 ; 142/142 Allele/fragme nt (bp) 1 1 142/149 65 29.7 6.7 Vi 1 Fig 1.4 Cont. E 5.0 * FC a* 2.2 1.7 4.1 0.0 1 : 1 1 LGO3:PR41; 337/337 1 337/312 1 337/337 J LGO3: Ma066a;1 142/142 66 3.8 337/312 1 142/149 Allele/fragme nt (bp) Figure 1.5: A-C. The two-way inter genomic region interactions between the major QTL region on LG 3 and the other QTLs on LGs 5, 6 and 8. (A) Inter loci interaction for PC a* between PR41 on LG 3 and PSIH3 on LG8. (B) Inter loci interaction for PC a"‘ between PR41 on LG 3 and BPPCT026 on LG5 (C) Inter loci interaction for SC] b* between PR41 on LG 3 and UDP96-001 on LG6 Means denoted by same letter within each graph are not significantly different at P < 0.05 (done using Least Squares Means, General Linear Model SAS 9.1). Units: L*, a* and b* (colorimeter reading) 67 A U E U11 1 L008. PSIH3; 270/270 270/280 270/270 1 270/280 1 LOW-PR41; 1 337/337 337/312 Allele/fragment (bp) 3 3.8 - 4'0 7 2.8a 3.1a 3.08 FC a* U U 1:1 2.0 - 0.0 Q - , 1 LGDS:BPPCF026;1 164/164 1 164/170 ‘ 164/164 1 164/170 11303: PR41; 337/337 337/312 Allele/fragme nt (bp) B C" C 40 b 4'0 23212,7a25a 4.0b 27a 34 SC1b* 1 ' ' ' 210 1:1 1:1 1:1 H H 15¢ 1 o tn tn ox : as 1 tn . tn 1 ex N v—' v— N N '-‘ F‘ N [(1)62UDP96-001;.: C 1 C : C C 1C C 1C 1 ON 1 ON 1 I—I 1 v—( o 1 a 1 .— ,._1 1 2 1 2 2 2 1 2 1 2 1 2 2 1 WWW“; 337/337 337/312 Allele/fmgme nt (bp) 68 Identification of QTLs for fruit skin and flesh color in sweet cherry is important for marker assisted breeding and to discover the underlying genes. Two previous studies by Fogle (1958) and Schmidt (1998) showed that, skin and flesh color in sweet cherry is a major genie trait. The bimodal pattern of data distribution for fruit color and the higher presence of mahogany skinned and red fleshed individuals in the segregating progenies are in agreement with the these studies. But higher heritability values for all the color metrics except red-green vector of lighter side of the blush cherries (SC2 a*), explain the very high genetic control of the fruit color in sweet cherry. However, this study suggests that minor genes may also control the variation for skin and flesh color in this cross. The higher correlation between skin and flesh color is in agreement with Fogle (1958) and Schmidt (1998). However, SC2 a* is not correlated to any other color metric. In blush fruits, SC2 a* is not very important as this location is yellow in color. But in mahogany color fruits, a* is important but less important compared to lightness/darkness (L*) and yellowness/blueness (b*) as the visual color is very dark blackish purple and that kind of color is more explained by L* and b*. This implies that SC2 a* is more subjected to environmental effects than any other color vector. The color development pattern of the skin and flesh with fruit maturity was in agreement with the previous study by Usenik et al. (2005) except in our study we observed that redness, a*, is also decreasing with time. However, Usenik’s study didn’t include any blush varieties and segregating populations, but the dark varieties he used, 69 Van, Sunburst and Elisa have different a* development compared to our dark fruited variety, NY54. The QTL analysis for fi'uit skin and flesh color in sweet cherry is challenging because the frequency distributions significantly deviate from normality. This has two consequences on the LOD score estimations; an increased Type 1 error rate and the inflated LOD values to levels where they cannot be compared between the different traits (Buil, 2005). The present study encountered these two problems and the MapQTL 5.0 manual (Van Ooijen, 2004) suggested that single marker analysis-Kruskalis Wallis Test could be used to verify the QTLs derived under such conditions. The QTLs presented in this paper were verified with that procedure but care must be taken when interpreting the inflated LOD scores for QTLs. The detection of a major QTL on LG3 for all the color metrics suggest that, pigmentation is controlled by a major gene on LG3. Four other QTLs on LGs 3, 5, 6 and 8 suggest that genetic control of mm color is also controlled by other genes with minor effects. However, very high R2 values for QTLs on LG3 suggest that the QTL on LG3 is the major gene. Previous studies suggested an epistatic interaction between one major and one minor gene. The present study is in agreement with those hypotheses and also suggested that the epistatic interactions would be more complex with different allelic states. 70 CONCLUSION This study identified a major QTL for skin and flesh color of sweet cherry on LG 3 and four minor QTLs on LG3, LG5, LG6 and LG8. The genomic regions and parental haplotypes in the QTL regions will serve as a basis for future fine mapping and candidate gene studies designed to determine the genetic change underlying the color QTL. In breeding perspective, this QTL information will expedite the production of sweet cherry varieties with desired skin and flesh colors. 71 LITERATURE CITED Bink MCAM, Boer MP, ter Braak CJ F, Jansen J, Voorrips RE, van de Weg WE (2008) Bayesian analysis of complex traits in pedigreed plant populations. Euphytica 161:85—96 Buil A, Dyer TD, Almasy L, Blangero J (2005) Smoothing of the bivariate LOD score for non-normal quantitative traits. BMC Genet 6 (Suppl 1):Sl 11 Clayton M, Biasi WV, Agar IT, Southwick SM, Mitcham EJ (2003) Postharvest quality of 'Bing’ cherries following preharvest treatment with hydrogen cyanamide, calcium ammonium nitrate, or gibberellic acid. HortScience 38:407—411 Crisosto CH, Crisosto GM, Metheney P (2003) Consumer acceptance of Brooks and Bing cherries is mainly dependent on fruit SSC and visual skin color. Postharvest Biol Tech 28: 1 59—167 Espley RV, Hellens RP, Puterill J, Kutty-Amma S, Allan AC (2007) Red coloration in apple fruit is due to the activity of a MYB transcription factor, MdMYBIO. Plant Journal 49:414—427 Facteau TJ, Chestnut NE, Rowe KE (1983) Relationship between fruit weight, firmness, and leaf/fruit ratio in Lambert and Bing sweet cherries. Can J Plant Sci 63:763—765 Fogle HW (1958) Inheritance of fruit color in sweet cherries {Prunus avium). J Heredity 49:294—298 Georgiev VS (1985) Some results with sweet cherry breeding in the research institute for fruit growing in Kustendil, Bulgaria. Acta Hortic 169:73—78 Gil M1, Tomas-Barberan FA, Hess-Pierce B, Kade, AA (2002) Antioxidant capacities, phenolic compounds, carotenoids, and vitamin C contents of nectarine, peach and plum cultivars from California. J Agric Food Chem 50:4976—4982 Hedtrich RT (1985) Sweet cherry breeding at the Swiss Federal Research Station I. Results of fruit characters and flowering period inheritance. Acta Hortic 169:51—62 72 Kita M, Kato M, Ban Y, Honda C, Yaegaki H, Ikoma Y, Moriguchi T (2007) Carotenoid accumulation in Japanese apricot (Prunus mume Siebold & Zucc.): molecular analysis of carotenogenic gene expression and ethylene regulation. J Agric Food Chem. 55:3414—3420 Li M, Boehnke M, Abecasis GR, Song PX (2006) Quantitative trait linkage analysis using Gaussian copulas. Genetics 173:2317—2327 Lyngstad L, Sekse L (1995) Economic aspects of developing a high quality sweet cherry product in Norway. Acta Hortic 379:313—320 Miller DC, Casavant KL, Buteau RJ (1986) An analysis of Japanese consumer preferences for Pacific Northwest and Japanese sweet cherries. Research Bulletin XB Washington State University, Agricultural Research Center. pp1—15 Olmstead JW, Sebolt AM, Cabrera A, Sooriyapathirana SS, Hammer S, Iriarte G, Wang D, Chen CY, Van Der Knapp E, Iezzoni AF (2008) Construction of an intra-specific sweet cherry (Prunus avium L.) genetic linkage map and synteny analysis with the Prunus reference map. Tree Genet Genomes 4:897—910 Rodrigues LC, Morales MR, Artur Joao Bartolo Femandes AJ B and Ortiz JM (2008) Morphological characterization of sweet and sour cherry cultivars in a germplasm bank at Portugal. Genet Resourse Crop Evol 552593—601 Sacks EJ and Francis DM (2001) Genetic and environmental variation for tomato flesh color in a population of modern breeding lines. J Am Soc Hortic Sci 26:221—226 Schmidt H (1998) On the basis of fruit color in sweet cherry. Acta Hortic 468:77—81 Tobutt KR, Boskovic R (1996) A cherry gene database. Acta Hortic 410: 147—1 54 Turner J, Seavert C, Colonna A, Long LE (2008) Consumer sensory evaluation of sweet cherry cultivars in Oregon, USA. Acta Hortic 795:781—786 Usenik V, Kastelec D, Stampar F (2005) Physicochemical changes of sweet cherry fruits related to application of gibberellic acid. Food Chemistry 90:663—671 73 Van Ooijen J W (2004) MapQTL® 5, sofiware for the mapping of quantitative trait loci in experimental populations. Kyazma BV, Wageningen, Netherlands Voorrips RE (2002) MapChart®: Software for the graphical presentation of linkage maps and QTLs. J Heredity 93:77—78 Wermund U, Feame A (2000) Key challenges facing the cherry supply chain in the UK. Acta Hortic 536:613—624 Zhang W, Chao S, Manthey F, Chicaiza O, Brevis JC, Echenique V, Dubcovsky J (2008) QTL analysis of pasta quality using a composite microsatellite and SNP map of durum wheat. Theor Appl Genet 11721361-1377 74 CHAPTER TWO GENETIC DIVERSITY ANALYSIS OF SWEET CHERRY (Prunus avium L.) CULTIVARS USING DNA MARKERS 75 INTRODUCTION Sweet cherry (Prunus avium L.), belonging to family Rosaceae, is an important temperate fruit crop. P. avium originated in central Asia and Europe where wild cherry, also P. avium, is an important timber tree. The wild cherries, landraces and improved cultivars represent the genetic diversity of P. avium (Iezzoni et al. 2008). Early settlers brought sweet cherry seeds and budwood to the New World from Europe. Most probably they would have brought a small number of selected land races from Europe. Early settlers in the New World selected the best sweet cherry seedlings such as “Bing” and landraces such as “Lambert” from the original material for the large scale planting. The advanced selections and the original material of sweet cherry brought to the New World represent the sweet cherry germplasm in the Pacific North West (PNW) region in North America. The PNW sweet cherry germplasm therefore, may have undergone genetic founder effect when early settlers selected seeds and budwood from the natural habitat to carry with them. Previous studies suggested that the PNW sweet cherry germplasm may have a narrow genetic base. The low genetic polymorphism was reported by Stockinger et al. (1996) and Gerlach and Stosser (1997) with randomly amplified polymorphic DNA (RAPD) markers, and Beaver et al. (1995) and Granger (1993) with isozyme markers. But no studies have been conducted to assess the genetic founder effect with more comprehensive simple sequence repeat (SSR) and gene based markers. If the genetic founder effect could be assessed with DNA markers with reference to the current genomic information of P. avium, it would provide a strong platform for germplasm enhancement and crop improvement of sweet cherry and tart cherry (P. cerasus), for whom P. avium was one of the two parents. We took the advantage of DNA markers and 76 linkage maps available from various studies for Prunus avium and other Prunus species (Clarke and Tobutt 2003; Dirlewanger et al. 2002; Joobeur et al. 1998; Dirlewanger et al. 2004; Olmstead et al. 2008) which could be used to estimate and visualize the genetic diversity at genome level. In the present study, the DNA polymorphisms among PNW sweet cherry germplasm (defined by 28 landraces and cultivars historically used and released in PNW region) (abbreviated as PNW from this point onwards), seven European sweet cherry land races which were not used in PNW sweet cherry breeding (abbreviated as non-PNW from this point onwards) and one wild cherry selection (New York 54) from Germany were compared using DNA markers to test the hypothesis of genetic founder effect in PNW sweet cherry germplasm. The specific objectives of this study were to, 1. Assess the genetic founder effect in PNW sweet cherry germplasm, diversity and genomic relationships among PNW, non-PNW and wild sweet cherry germplasm groups. 2. Examine the level of heterozygosity and allele diversity across the cherry genome. 3. Define a subset (panel of six individuals) of P. avium selections for single nucleotide polymorphism (SNP) detection to develop high throughput DNA markers. 4. Recommend a panel of few DNA markers that can effectively be used for in-house P. avium DNA fingerprinting purposes without any ambiguity. 77 MATERIALS AND METHODS Plant materials Thirty-six P. avium selections were chosen for the study that represented PNW sweet cherry germplasm (defined by 28 landraces and cultivars historically used and released in PNW breeding programs), seven European sweet land races which were not used in PNW sweet cherry breeding and one wild cherry selection (New York 54) (Table 2.1). Leaves were collected from trees growing at Michigan State University’s Clarksville Horticultural Research Station, Clarksville, Michigan and the North West Horticultural Research Station, Traverse City, Michigan or Washington State University’s Irrigated Agricultural Research Center, Prosser, Washington. Immature and actively growing leaf samples were collected from all the selections in early spring, placed immediately in dry ice, moved to the laboratory and frozen for 24 hours at 80 0C. The frozen leaf samples were freeze dried for 48 to 72 hours and stored at -20°C until DNA extraction. DNA extraction and genotyping DNA was extracted using the cetyl trimethylammonium method described by Stockinger et al. (1996). PCR conditions were as in Olmstead et al. 2008 except for the EMPA and EMPAS markers, where, touch-down PCR temperature profile was used (Clarke and Tobutt 2003). The S-locus was genotyped using the S-RNase allele-specific 78 primers, S1 -S6 (Sonneveld et al. 2001), S7-Sg and 8.2 (Sonneveld et al. 2003). The gene or expression sequence tag (EST) based markers (PR markers) were genotyped according to the method described by Olmstead et al. (2008). SSR markers were size separated in 6% denaturing poly acrylamide gels and visualized using silver stain (Bio-Rad Laboratories, Hercules, CA, USA). The S-RNase and PR markers were resolved in 4% agarose gels. Data analysis The different alleles for each marker were identified by fragment base pair (bp) size for SSR and PR markers and as nominal data for the S—locus. Some of the sweet cherry selections were related, e. g. parents or grandparents, and the marker genotypes for these individuals were checked to verify that these genotypes were consistent with the pedigree relationships (see Table 2.1 for pedigree information). Additionally, three populations were available from the crosses between New York 54 (N Y54) and Emperor Francis (EF) (NY x EF: 190 individuals, Olmstead et al. 2008), Powdery Mildew Resistant-l (PMRl) and Rainier (PMRl x Rainier: 108 individuals), PMRl and Bing (PMRl x Bing: six individuals) and PMRl and Van (PMRl x Van: five individuals) (Olmstead 2001). These crosses were used to validate the inheritance pattern of the alleles and to detect the presence of null alleles. The confirmed null alleles were designated as $8 and unconfirmed null alleles which potentially could be homozygous were designated as $ following the format used for FlerTL® (Bink et al. 2008). The markers, whose putative alleles showed inconsistent segregation patterns, duplicate or multiple loci, or stutter bands/smears were not included in the analysis. 79 The unique alleles (UA) for each cultivar and for PNW and non-PNW groups were identified. The percentage of heterozygous loci (% H) for each sweet cherry selection was calculated as the proportion of heterozygous loci out of total number of marker loci scored for that cultivar. The frequency of each allele of marker (p,) was calculated and used to estimate heterozygosity (H) and polymorphic information content (PIC) for the 77 DNA markers. The H and PIC were calculated as explained in Botstein (1980) and Shete et al. (2000) using the following formula: Pi is the frequency of 14" allele, and n is the number of alleles. H =1— :piz i=1 n n—l n PIC = 1-21912 -1 2 21712ij 1 i=1 i=1 j=i+l The allele frequencies were classified to identify the rare alleles and to see their presence or absence in the PNW sweet cherry germplasm. Allele data were converted to the binary format (1: presence of the allele and O: absence of the allele for a given P. avium selection) and a dendrogram was constructed using the UPGMA method of McQuitty linkage (McQuitty and Koch 1975) and Absolute Correlation Coefficient Distance (Minitab 15.0) to show the genetic relatedness among the 36 selections. 80 The distribution of alleles for marker loci along the linkage groups of P. avium (Olmstead et al. 2008) was examined to identify the genomic areas where non-PNW and wild type alleles were detected. The %H for all the linkage groups were examined for PNW, non-PNW and wild P. avium groups. The graphical genotypes (GGT) for all the linkage groups (LG) of all 36 selections were illustrated to visually represent the alleles of all the loci across the sweet cherry genome. 81 RESULTS AND DISCUSSION Unique and rare alleles A total of 300 alleles were identified for 77 DNA markers from the 36 sweet cherry selections (Table 2.2 and Figure 2.1). 52 unique alleles (UA) (an allele only found in a single sweet cherry selection) out of 300 alleles were identified, 40 of which were not detected in the PNW sweet cherry germplasm. The wild selection, NY54, had the highest number (13) of UA followed by the European landraces, Ambrunus (had nine UA) and Cristobalina (had six UA) (Table 2.1). The higher presence of UA outside the PNW sweet cherry germplasm support our hypothesis that PNW sweet cherry germplasm had been undergone the genetic founder effect when early settlers brought sweet cherry germplasm to the New World. The frequency for all 300 alleles showed that rare alleles (those alleles with frequency of less than 0.20) were more common (147) and notably 44 out of the 147 alleles (30%) were absent in the PNW sweet cherry germplasm (Table 2.2 and Figures 2.1 and 2.2). The 30% absence of rare alleles also validates the hypothesis of genetic founder effect in PNW sweet cherry germplasm. Allele diversity and cultivar heterozygosity A total of 256, 253 and 112 alleles were detected in PNW, non-PNW and wild sweet cherry groups respectively. All three groups shared 31% of total alleles detected) (Figure 2.1). PNW and non-PNW group shared 74% of total alleles showing that they 82 were evolutionary more related than their individual relationships to wild cherry. The PNW and non-PNW groups shared 32% of total alleles with wild cherry (Figure 2.1). The percentage of heterozygous loci (%H) was highest in EF. This bias resulted from the initial marker screening to identify allele polymorphism was based on EF and wild cherry, NY54 (Olmstead et al. 2008). However, all the %H values for the other 34 selections and groups were not significantly different (Table 2.1) (statistical analysis is not shown). This is due to the facts that P. avium maintain higher level of genetic heterozygosity through the reproductive mechanism of self incompatibility and the heterozygosity for cultivars with no progeny or pedigree data available cannot be exactly determined due to the presence of possible null alleles. Therefore, the cultivar %H is not a good parameter to test the hypothesis of genetic founder effect. The % H for individual linkage groups (LG) of PNW, non-PNW and wild P. avium groups were also compared and only LG8 for PNW and non-PNW had lower level of H compared to other LGs and also compared to the LG8 of NY54 (Table 2.3). This could lead to the hypothesis that LG8 may contain many important agronomic traits and therefore, subjected to more intense selection in the processes of domestication and breeding (Table 2.3). A total of 44 alleles were detected from the eight European landraces and wild cherry which were not present in the PNW sweet cherry germplasm (Tables 2.1, 2.4-2.11 and Figure 2.1). The genomic locations of these 44 alleles were identified and their distribution among the eight P. avium linkage groups were graphically displayed along with other alleles (Figure 2.2). A total of l 1, 7, 5, 4, 5, 7, 2 and 3 alleles which were 83 novel to PNW sweet cherry breeding germplasm were detected on LGs 1, 2, 3, 4, 5, 6, 7 and 8 respectively. These allele numbers indicate that LGs l to 6 has undergone the genetic founder effect than that of LGs 7 and 8. In figure 2.2 on each LG, the names of European landraces or NY54 which provide the novel alleles are shown. LGs 1, 2 and 6 showed that UA were widely spread along the LGs. Implying the missing DNA diversity as a whole LG8. LGs 7 and 8 were least diverse in terms of UA. Only wild cherry, NY54 and Katalin brought UA to LG7, and NY54, l9-21B and Eugenia brought UA to LG8. 84 Table 2.1: The Prunus avium groups, selections (wild, Non-PNW and PNW), their parents, origins, number of unique alleles (UA) and % of heterozygous loci (H) Group Selection Parent 1 Parent 2 Origin UA H Class H Wild NY54 U3 U Germany 13 49.4 49.4 l9-2 l B U U Ukraine 1 36.9 Ambrunes U U Spain 9 50.1 Cristobalina U U Spain 6 39.4 1:311” Eugenia U U Nb_ Europe 4 54.9 46-5 Katalin U U Hungary 4 43.8 Krupnoplodnaya U U Romania 1 50.6 Windsor U U N. Europe 2 49.8 Emperor Francis U U N. Europe 4 79.8 Benton Stella Beaulieu USA 0 57.4 Bing Black-Republican U USA 0 63.7 Brooks Rainier Early-Burlat USA 0 48.6 Chelan Stella Beaulieu USA 0 49.0 Chinook Bing Gil-Peck USA 0 52.2 Glacier Stella Early-Burlat USA I 50.8 Lambert U U USA 1 45.2 Lapins Van Stella USA 0 50.9 Napoleon U U Germany 0 59.1 Newstarc U U Canada 0 49.7 PC7147-009 Stella U USA I 49.3 PC7903-002 PC7147-4 PC7 146-1 1 USA 0 49.6 PC8007-002 Glacier Cashmere USA 0 43.6 PNW PMR-l u U USA 0 42.7 53:6 Rainier Bing Van USA 0 58.1 Regina Schneiders Rube Germany 4 54.9 Same V-l 6U l4U U Canada 0 51.] Schmidt U U Germany 0 69.3 Schneiders U U Germany 0 52.2 Selah P8-79 Stella USA 0 47.4 Stellac Lambert JI242U Canada 0 63.3 Summitc Van Sam Canada 0 39. l Sweetheartc Van Newstar Canada 0 51 .4 Tieton Stella Early-Burlat USA I 56.9 Ulster Schmidt Lambert USA 0 55.3 Vanc Empress-Eugenie U Canada 0 58. 1 Vice Bing Schmidt Canada 0 52.1 aU: Unknown, bN: Northern, cConsidered as PNW germplasm (closely related to other PNW selections) 85 Figure 2.1: The number of unique and shared alleles identified in the three groups of sweet cherry used in the study; PNW: 28 cultivars historically used and released in the Pacific North West sweet cherry breeding programs, Non-PNW: seven sweet cherry cultivars from Europe that have not been used in the PNW sweet cherry breeding programs and Wild: one forest (mazzard) cherry (Prunus avium) selection (N Y54) 86 Table 2.2: The relative abundance of alleles with differing frequencies detected for 77 DNA markers Number of alleles of each Number Of alleles class that are not present in Allele frequency class within each class PNW <0.20 147 44 0.20 - <0.40 77 0 0.40 - <0.60 50 0 0.60 - <0.80 22 0 0.80 - <1.00 4 0 Total number of alleles 300 44 87 Table 2.3: The percentage of heterozygous loci (H) per linkage group Number LG of loci PNW Non-PNW Wild (N Y54) Total per LG 1 13 54.8 50.6 30.8 48 2 12 50.5 34.4 58.3 38 3 9 68.9 54.7 22.2 52 4 8 43.4 44.9 37.5 36 5 11 60.6 62.8 50.0 51 6 9 60.2 53.1 66.7 39 7 10 61.3 49.0 70.0 61 8 5 27.4 35.0 60.0 28 Total 77 53.4 48.1 49.4 44 88 Table 2.4: The possession of marker-alleles by sweet cherry selections - LGI Map Position M k Allele Number of selections If Number of selections possesing the (cM) ar er (bp) possesing the allele allele is less than 3, selection names 0.0 CPPCTOI6 171 13 ISO 22 188 4 190 l Katalin 198 1 Regina 200 ] Ambrunus 204 l Katalin 208 l6 1 .0 EMPAOOI 1 3 5 l Cristobalina MS I PC7147-009 150 5 155 I] 158 l PMR-l 160 I3 I65 2| 37.8 EMPAOOS 225 l Cristobalina 240 4 245 I7 255 27 45.1 EPDCUSIOO 184 7 I95 2 EF, Schmidt I98 7 202 1 Cristobalina 47.7 UCD-CH3l I45 24 150 12 155 7 I65 12 l 70 l Krupnoplodnaya 50.0 PR33 244 25 250 2 Windsor, Sam 266 24 63 .6 PCeGA59 184 28 190 26 64.9 CPSCT027 204 33 216 5 218 23 220 l Ambrunus 85.1 PMS67 I48 26 160 9 162 4 165 22 88.1 PRIOI 146 l NY54 152 36 158 6 l06.6 CPPCTOl9 180 3] I86 8 188 l Ambrunus I90 1 EF 110.0 EMPAOI l 240 32 245 12 250 l Ambrunus 116.0 EPPB42 l 3 132 l EF 140 34 I46 5 Table 2.5: The possession of marker-alleles by sweet cherry selections - LGZ Map Position Marker Allele Number of selections If Number of selections possesing the (cM) (bp) possesing the allele allele is less than 3, selection names 0.0 MA069a 105 l Wnidsor 120 36 126 I4 I30 I Lambert 1.5 CPSCT038 I90 32 I92 9 204 I0 4.] UDA-059 134 28 138 8 I I BPPCTO34 225 I8 235 I2 250 2 Schmidt, Ulster 255 I6 12.7 MA005c I90 26 I98 25 I58 UDAp-46I 159 I5 I78 32 23.7 BPPCTOOZ I68 I NY54 I84 36 185 9 186 14 32.4 MA007a 93 I NY54 104 I9 110 I0 I I6 22 I26 I Cristobalina 40.7 U DA-005 2 I 8 35 222 22 224 I 46.4 UCD-CHIZ 175 26 I80 I I I82 8 I86 I I9-2 I B 190 4 I92 I I 55.7 PCeGA34 135 I2 I43 9 I45 I NY54 155 I EF I65 I NY54 59.7 CPSCTO37 I90 7 195 I3 2 IO 32 90 Table 2.6: The possession of marker-alleles by sweet cherry selections - L03 Map Position Marker Allele Number of selections If Number of selections possesing the (CM) (bp) possesing the allele allele is less than 3, selection names 0.0 EPPCU599O 185 27 195 28 0.1 PaClTA4 I40 29 143 27 23.2 PMS30 I32 4 I42 24 152 7 I62 7 I70 7 175 17 25.8 BPPCT039 128 I Cristobalina 134 15 -.. 138 14 140 2 Ambrunus, Regina I45 23 32.4 EPDCU3083 145 24 153 26 34.1 UDP98-416 200 I8 210 33 39.4 CPDCTO37 145 6 1 5 5 1 Cristobalina 158 2 Ambrunus, Windsor 160 10 165 8 I70 25 47.5 MA039a I70 34 216 l l 220 4 222 1 Regina 72.6 EMPAOM 220 I Ambrunus 225 10 230 27 232 3 Cristobalina, Napoleon, Lambert 233 8 234 4 235 8 91 Table 2.7: The possession of marker-alleles by sweet cherry selections - LG4 Map Position Marker Allele Number of selections If Number of selections possesing the (cM) (bp) possesing the allele allele is less than 3, selection names 0.0 EPPCU3664 I 15 II 122 31 125 6 130 9 6.4 EMPAOIS 220 14 222 13 225 1 NY54 240 9 13.1 AMPAIIO 135 34 138 14 33.8 BPPCT040 120 1 1 125 12 128 1 EF 1 30 l Cristobalina I35 9 145 17 45.0 UDP97-402 1 18 I NY54 I22 I NY54 126 3 Cristobalina, EF, Stella I30 5 138 6 50.0 M 12a 180 33 185 10 190 l Eugenia 59.5 UDA-037 423 5 425 l l 431 20 73.7 UDA-027 135 36 137 16 92 Table 2.8: The possession of marker-alleles by sweet cherry selections - LGS Map Position Marker Allele Number of selections lf Number of selections possesing the (cM) (bp) possesing the allele allele is less than 3, selection names 0.0 EPPCUO961 I46 20 148 27 150 15 7.7 EPPCU9168 162 13 I64 8 I68 25 20.7 BPPCT026 164 24 170 17 I78 5 I86 14 38.4 UDP96-019 202 22 205 22 47.4 BPPCT037 137 5 142 13 145 15 148 18 155 4 157 1 Windsor 49.0 EMPaS] 1 68 16 78 22 88 3 NY54, 19-21B, Ambrunus 108 4 112 10 61.9 EPDCU5183 120 20 125 2 Cristobalina, Schneiders 140 4 145 I Krupnoplodnaya 150 8 65.0 CPDCT016 150 16 160 33 70.5 EPPB4230 253 9 254 7 255 1 Ambrunus 256 24 260 7 73.4 CPDCT022 145 3 NY54, Regina, Tieton 150 19 155 l I 158 l Ambrunus 165 7 175 6 75.5 BPPCT014 190 22 192 3 Eugenia, EF, Schmidt 195 — kl! 93 Table 2.9: The possession of marker-alleles by sweet cherry selections - LG6 Map Position Marker Allele Number of selections If Number of selections possesing the (cM) (bp) possesing the allele allele is less than 3, selection names 0.0 EMPaSOI 222 5 228 27 232 18 240 1 Glacier 4.5 UDP96-001 110 1 Ambrunus 115 7 129 28 131 15 13.5 BPPCT 008 90 8 97 31 100 4 36.6 CPPCT023 170 7 I71 5 44 EPPCU3090 172 25 NY54 180 1 185 27 50.8 UDP98-021 102 27 112 24 118 1 NY54 51.3 EPPB4227 120 1 Tieton 125 1 NY54 130 19 I35 32 145 4 59.4 MA040a 210 20 215 1 Eugenia 225 '12 240 6 66.8 S-Rnase S-1 9 S-2 6 S-3 18 S-4 21 S-5 2 Krupnoplodnaya, PC7903-002 S-6 3 NY54, Ambrunus, Eugenia S-7 1 Eugenia S-9 10 S-12 2 Katalin, Schneiders 94 Table 2.10: The possession of marker-alleles by sweet chen'y selections - LG7 Map Position Marker Allele Number of selections If Number of selections possesing the (cM) (bp) possesing the allele allele is less than 3, selection names 0.0 CPPCT022 245 25 250 26 252 3 NY54, Chinook, Regina 13.1 UDAp-407 205 15 215 30 217 2 PC8007-002, PMR—I 14.0 CPSCT026 178 17 180 5 14.5 UDAp-401 260 21 265 14 270 5 295 7 15.5 EPDCU2931 132 15 146 3 Napoleon, Windsor, Lambert 148 5 150 1 Katalin 152 23 160 1 NY54 30.3 CPPCT033 145 10 148 12 149 4 150 13 152 3 EF, Schmidt, Vic 158 3 164 13 38.2 PMS2 130 8 142 22 146 24 165 4 42.4 PS8e08 172 8 181 27 186 17 45.0 PCHCMS2 670 18 730 28 49.6 EPDCU3392 110 12 I 15 I6 123 7 129 20 135 5 95 Table 2.11: The possession of marker—alleles by sweet cherry selections - L08 Map Position Marker Allele Number of selections lf Number of selections possesing the (cM) (bp) possesing the allele allele is less than 3, selection names 0.0 pchgms49 1 56 35 168 I 1 170 3 Benton, Chelan, Tieton 173 2 13.4 EPPCU4726 160 34 I62 2 24.4 CPPCT006 188 4 190 29 204 1 Regina 206 2 NY54, 19-21B 208 14 54.6 MD201a 230 34 250 6 80.8 PSlH3 270 34 272 5 275 9 280 1 NY54 285 1 Eugenia 96 Figure 2.2: A-H. The different alleles for the markers and their relative presence in all the linkage groups for 36 sweet cherry selections {wild cherry (gray bar), PNW (white bar) and non-PNW (black bar) groups}. The arrows show the alleles that do not exist in the PNW sweet cherry cultivars and the names of the cultivars are indicated near the arrows. A: linkage group (LG) 1, B: LG2, C: LG3, D: LG4, E: LG5, F: LG6, G: LG7, H: LG8 97 Fig 2.2 Cont. A: Linkage group 1 14bbp 116.0 cM 140bp F _ EPPB4213 132m) . 110.0 cM 32222 E‘— Ambr‘fm‘ EMPAOII 240bp 1 - 190bp 106.6 cM 188bp—i é—Ambrunus CPPCT019 186bp_. 180bp :— - _:1 88.1 cM PR 101 $3? 1.__.L . -1 146bp ,- :NY54 85.1 cM }232P 1:, “ PMS67 160bp_ 14ng E . 64. 9 cM 3233p h <——Ambrunus 1 CPSCT027 2166‘” E 18313" — ' p — 1 63.6 cM GA59 184bp— _ 50.0 cM PR33 32222 .3— ' 244bn - - ___1_7_0bp 1 <— Krupnoplodnaya 165bp ,- 37898‘1131 12331-1: - p "—21:- 145bp l—F J 202b *—-Cristobalina 45.1 CM 198153;: EPDCUSIOO 1951:1511: l84bp :- 25 5bp _ 37-8 CM 245bp _ I EMPAOOS _ 240bp 1 :2 225bp é—Cristobalina 165bp 3 1601311 1.0 CM 158bp EMPAOOI 155.121). 150bp _____ <— Cristobalina 204pr” 4—Katalin 0.0 CM 28%)?) <—-Ambrunus CPPCW #19011: {—181.11 188bp 180bp 3 l7lbp 1 IF! 1 _ __ . 0 10 20 3O 40 lNon-PNW alleles El PNW alleles fl Mazzard alleles Number of alleles 98 Fig 2.2 Cont. B: Linkage group 2 59.7 CM 3222;: _ — CPSCT037 1 90bp “165bp“; 4—NY54 55.7 cM 155bp_____ PCeGA34 145bp ‘1- <—NY54 '143bp —:1 l35bp _: ..,1?2b12. ' 190bp 46-4 0M ' 186bp 4—19-21B UCD-CH12 182bp 180bp 175bp — n 40.7 cM 3.2.2.41)me UDA-OOS 222bp 218bp - , 126bp I <—Crist0balina 32.4 cM “6131’. . ' MA007a 3110bp 104bp ,— J 93bp ”h <—NY54 l86bp ‘-:I 23'7 CM 185bp -: BPPCT002 184bp " n 168bp MS—NY54 15.8 cM 178122, UDAp461 159bp h: 12.7 CM 4 198bp T— 1 MA005c 190bp % 111111111 255bp _:m 11.0 CM 2501319 :1 BPPCT034 235bp F: 225bp 4.1cM _l38bp_ :1 UDA-059 134bp — 204bp h: 1.5 cM 7 192bp_ :18: CPSCT038 190bp . 0.0 cM ”Ob? F’ M 069 126bp _ _:1 a a 120bp. ; m 105bp F‘—Windsor 4| 1 1 4‘ 0 10 20 30 4O INon-PNW alleles El PNW alleles I Mazzard alleles Number Of alleles 99 Fig 2.2 Cont. C: Linkage group 3 72.6 cM EMPA014 I 47.5 cM MaO39a J 39.4 cM 11----..-..---.. CPDCT037 15312423- 4——Ambrunus $13:pr <-——'Cristobalina 145bp . 34.1 cM 121.9212- i UDP98-416 200bp J- I 32.4 cM 111153131311- ‘ EPDCU3083 l45bp ‘ " ' 1-1.4.5991) ' 25.8 cM __ 11410191311 BPPCT039 1128911.. 1111-: 134bp J 128bpw 4—Cristobalina 12§b8 ' 1170581- 23.2 cM __.1.62.bp---:' PMS30 3135321212 E 114% 1 '13sz E 0.1cM PaClTA4 5313.12.11i i 40bp 4- I 0.0 cM 111125119111,— ' EPPCU5990 185bp _ 11" 0 10 20 30 40 I Non-PNW alleles E1 PNW alleles Mazzard alleles Number of alleles 100 Fig 2.2 Cont. D: Linkage group 4 7326M Wl37bp _:::1 43lbp _:1 59'5CM 425bp ‘3 UDA-037 3. 4 423bp 190bp I<—-Eugenia 50'0 CM 185bp -:1 M12a ...... , 180bp — J 138bp :1 130bp 4: 45.0 cM - UDP97-402 1126b!) .3 122bp m<———NY54 118bp HRH—NY54 145bp -:m l35bp -: 33,8 cM 130bp I"—'Cristobalina BPPCT040 128bp :1 125bp 7-: 13.1cM 138bp -: AMPA110 135bp — i 240bp i:m 6-4 CM 225bp STE—NY54 EMPAOlS ~ EPPCU3 664 0.0 cM l25bp — 1‘1pr -: 0 10 20 30 40 INon-PNW alleles El PNW alleles I Mazzard alleles Number Of alleles 101 Fig 2.2 Cont. E: Linkage group 5 75557 1333" r BPPCT014 190bp _ _ 175bp :n 165bp -: 73'4 CM 158bp I<-—Ambrunus CPDCT022 155bp -: 150bp _ I 145bp :Il 260bp_ I: 256b _ II 70.5 CM ”2551): i4—Ambrunus EPPB4230 254bp 4.: 25%;; :m 65.0 cM 160pr24 I CPDCT016 150bp _:ml 150bp :11: 61.9 CM 423:: ”I é—Krupnoplodnaya EPDCU5183 125131) :1 12%;; T I 112bp :2 .1.08bp F33 49-0 CM , 88bp -l‘—NY54,19-21B,Ambrunus 68bp -: 157bp ls—Windsor 4155bp -:l 474 cM l48bp ,, —:mm BPPCT037 _ 145bp 1-:I 1421,97: 137bp I: 38.4 cM 205bp 7 — 1 UDP96-019 202bp ‘ 5557777 1861313 —:1 20.7 cM ,178bp #2 BPPCT026 “170bp I: 164bp 7.7 cM 123? :— W" P,.-:' EPPCU9168 162bp :4 0.0 cM 150pr I: EPPCUO961 .148bp . “1.. 146bp — I y 0 10 20 30 40 Number of alleles INon-PNW alleles D PNW alleles I Mazzard alleles 102 Fig 2.2 Cont. F: Linkage group 6 .5-12 F3 S-9 -: S-7 I<——Eugenia 66.8 cM Sf6 .- ‘—— NY54, Ambrunus, Eugenia S—Rnase S-5 I] S-4 -_ fl S-27 —1111 s-1 i: 240bp 44': 59.4 cM 225bp .2111 Ma040a 21 prg 1 I ‘——Eugenia 210bp 1- *1 .. 1.4.5.152 :2 51.3 cM .1352?» ‘ EPPB4227 .130bP .1 I“ .I.21.5_b_p_..1-<-—NY54 l20bp 121 50.8 cM 1181’? .im T—NY54 UDP98-021 ”1712,1594: fl 102bp _; *1 44.0 cM 1 18,51,313. —: fl EPPCU3090 _ 1,80bp I ‘—NY54 l72bp [1 m 36.6 cM 17lbp Fm CPPCT023 170bp —m 13.5 CM . lOObpr :1 BPPCT008 97bp 1 fl 90bp 131bp‘ —:m 4.5 CM 129bp — W UDP96-001 ”115bp " :: 110bp Ih—Ambrunus 240bp :1 00 cM 232bp E EMPASO] 228bp ., ii 111 222bp 4 , . 0 10 20 30 40 Number of alleles I Non-PNW alleles D PNW alleles ll Mazzard alleles Fig 2.2 Cont. G: Linkage group 7 135bp E 49.6 cM 129bp 1 ' EPDCU3392 123138—31 115bp 110bp -: 45.0 cM 730bp ‘ - PCHCMS2 H670bp 4244 cM 441486bp : P88e08 1811’10 . .111. 172bp -: 165bp -: 38.2 cM 146bp — 1 PMSZ l42bp 130bp —m 4164bp4 I:1 1581,51) I- 303 cM 15sz :' CPPCT033 150bp -: 149bp _] 11.58.61 -:7 145bp —: 160bp Il<—NY54 .15.pr — 4 15.5 CM 44150bp I4—Katalin EPDCU2931 1481915 F: 146bp4_-:] 132bp —:I 295bp 44:: 14.5 cM 270bp Cm UDAp-40l 265bp -: 260bp - 1 14.0 cM 180bp -:m CPSCT026 l78bp ———-‘—‘——m 13.1cM 217"? :’ UDAp-407 2151’? _ " 205bp _:m 0.0 cM 2521’? 1:“ CPPCT022 2501913 . 245bp 4 _: 4 4 0 10 20 3O 40 Number of alleles I Non-PNW alleles D PNW alleles I Mazzard alleles 104 Fig 2.2 Cont. H: Linkage group 8 285bp I_Eugenia 280bp l+—NY54 80.8 cM PS1H3 E7_51_me-::l 272bp I: 270158 - 54.6 CM 2501),) u MD201a .1 .3 250515 I I 208bp - I 206913 .4—NY54, 19-2113 24.4cM . CPPCTOO6 204bp J 190bp ‘- 4 188bp I] 13.4 cM EPPCU4726 0.0 cM pChgms49 0 10 20 30 40 Number of alleles INon-PNW alleles El PNW alleles I Mazzard alleles 105 Genetic diversity structure The phylogenetic relationships among the 36 cherry selections were determined using the data from the 77 DNA markers (Figure 2.3). At ~75% of genetic similarity value, the selections could be classified into 8 clusters (A-H). The clusters A and D exclusively represent European selections. NY54, a wild cherry is genetically dissimilar from all the other ones studied and has 70% genetic similarity to two Spanish landraces, Cristobalina and Ambrunus. NY54, Cristobalina and Ambrunus as a single cluster (cluster A) were separated from the rest of the cultivars at 40% of genetic dissimilarity value. The cluster E contains Vic, whose parents are Schmidt and Bing. In this study, Vic clustered with Schmidt. The clusters B, C, G and H include PNW sweet cherry breeding germplasm. Grouping of two European selections, Windsor and Eugenia that do not have any known pedigree relationship to the PNW cultivars, with clusters C and B, suggest the close genetic relationship of these selections to the parents that have been used in the PNW sweet cherry breeding. 106 Figure 2.3: Dendrogram resulting from marker allele based genetic distance analysis of 36 sweet cherry selections. Cluster analysis used McQuitty linkage, Absolute Correlation Coefficient Distance (Minitab 15) 107 Similarity 100.00 86.83 73.65 60.48 (A) NY54 Ambrunes Cristob alina J (B) BF Eugenia Lapins .. Sweetheart—} — Rainier Van I Selah Bing — Nap ole on - :— Chinook Lambert Newstar J l — Stella Ulster PC7147-009 Summit I — Sam ,.___Windm_ (D) Katalin Schneiders I Renae... (E) l9-2lB Schmidt-———l Vic-———J F Krupnoplod 4 IIIIENIIZIIImImagflolgHII G Benton ( ) Glacier ] PCSN'LOOZ 7 Brooks (H) Tieton I 108 Graphical genotypes for sweet cherry cultivars The genetic diversity analysis used DNA markers that covered all eight sweet cherry linkage groups. Thus it was possible to visualize the linkage group heterozygosity for the 36 sweet cherry selections and present it as graphical genotypes (GGT) (Figure 2.4). The GGT illustrate the marker alleles for the eight linkage groups using the map positions from the consensus linkage group based on the data of Olmstead et al. (2008). The GGT can be used to search for those selections that have marker alleles that are 4 linked to favorable QTL alleles. For example, Zhang et al. (2009) identified two QTLs for fruit size on LG2 and LG6 segregating in the NY54 x EF mapping population. r BPPCT034 was found to be linked to the LG2 fruit size QTL. In our study four alleles were identified for BPPCT034 (PIC of 0.6) indicating that this would be a good marker candidate for fine mapping and validation of the QTL. EPPCU3090 on LG6 was associated with the second QTL identified. In our study three alleles were identified for EPPCU3090 (PIC value of 0.4) therefore, it is also a useful marker to further investigate the LG6 fruit size QTL. Similarly the GGT could be correlated to mapped genes and QTLs to get more insight for the marker haplotype information which will be useful in marker assisted breeding and future functional genomic studies. The only drawback in these GGT is that the exact allele phase (i.e. coupling and repulsion) for markers for some P. avium selections cannot be represented as for those selections; marker data for segregating progeny populations are not available. GGT for sweet cherry cultivars show the allelic states and genomic landscape with respect to studied DNA markers and the consensus linkage map positions. However, 109 few mapped QTL are available to fully utilize this resource. The extensive phenotyping for important traits in multiple years and locations is necessary to assign breeding values to the linked alleles and marker allele haplotypes. This will allow the GGT to be used in marker assisted breeding and comparative genomics in family Rosaceae. 110 Figure 2.4: A-H Graphical genotypes for 36 sweet cherry cultivars. Eight linkage groups for each cultivar are shown with two homologous chromosomes for each linkage group. The marker positions in centi Morgan (cM) and marker names are shown on the left. In each cell, the allele in base pairs is shown for the SSR and gene based (PR markers and the allele name in number is shown for the S-locus. $$ indicates a confirmed null allele 6‘ 9, and $ indicates an unconfirmed null allele. represents the missing data. The blank cells represent the gaps in the linkage groups. 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V O oOmO momOmSO smorObnOAOU o O V1w9OnOD mwOmDUDAOmO OMOOwanOm OmmV/OAO V<1O1O0waO OOOmDUAOAOmO Jamew ONO. mNV Vdm O.Vm V.Nm w.mN N.mN (we) uopysod dew g g V 9981M 982w away—:5 "0 .280 V.N ME. 123 mmO hmO a mmO mmO NNO mmO an mmO hmO m mmO a mmO mmO mmO mmO m OmV m OmV m mNV m OmV 1 1 mNV OmV m mNV 1 MNV mNV 1 OOO 1 owO OwO mwO 1 owO OwO OOO 1 OwO 1 OOO mwO 1 OOO 1 1 1 1 1 1 1 1 1 1 1 ONO 1 1 1 wOO NNO mmO mVO mNO mmO mNO mVO 1 1 m mmO m OmO mNO mmO mVO mVO mVO mmO me a mmO a mmO m mmO mmO me mmO me mmO me mmO mmO mmO 1 ONN NNN OVN ONN NNN 1 OVN 1 1 1 NNN 1 1 1 mNN OVN mOO NNO NNO OmO NNO mNO NNO mNO mOO NNO mOO NNO NNO mNO OmO NNO mNO «a mm M W W X mo w. W a m m. 1w rm 9 Q0 10+ 0.. . A w. «d. 0 m1 9 0.. m WW 0 m m m. m. m. W. m. 8 m nr w 8 mm \1NO1O NOVSOAOQD OVO1O102OnOmO OO OO< m OOOmO VccmDUAOnOmO Jaxxew 5mm mdm Odm O.mV w.mm O.mO 9. 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