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EVALUATECN AND SELECTION OF CARROT
BREEDING MATEREAL FOR SUGAR CONTENT,

DEY MATTER AND $OLUBLE SOLQDS

Thesis for the Degree of M. S.
MICHEGAN STATE UNIVERSITY

Bruce Charles Carlton
1958

EVALUATION AND SELECTION OF CARROT BREEDING MATERIAL

FOR SUGAR CONTENT, DRY MATTER AND SOLUBLE SOLIDS

BRUCE CHARLES CARLTON

AN ABSTRACT

Submitted to the College of Agriculture, Michigan State University of
Agriculture and Applied Science in partial fulfillment of
the requirements for the degree of

MASTER OF SCIENCE

Department of Horticulture

1958

Approved %n/v

BRUCE CHARLES CARLTON ABSTRACT

Analysis of dried carrot roots forsoluble solids, sugars, and dry
matter content showed much more variation between individual roots with-
in a variety than between variety means. The extreme ranges within varie-
ties indicate that, through inbreeding and hybridization, it should be pos-
sible to develop uniform varieties with levels of dry matter and sugar con-
tents approximating the extremes observed. In individual roots the highest
dry matter content observed was 13. 3 and the lowest was 7. 7 per cent,
while total sugars ranged from 6. 41 to l. 92, and soluble solids from 9. O
to 4. 5 per cent on a fresh weight basis.

Correlation coefficients and regressions show that both dry matter
and total sugars can be estimated with reasonable accuracy from soluble
solids as determined by the refractometer. By this method, rapid and
efficient selection of carrot breeding material for dry matter and total

sugars can be accomplished.

EVALUATION AND SELECTION OF CARROT BREEDING MATERIAL

FOR SUGAR CONTENT, DRY MATTER AND SOLUBLE SOLIDS

By

BRUCE CHARLES CARLTON

A THESIS

Submitted to the College of Agriculture, Michigan State University of
Agriculture and Applied Science in partial fulfillment of
the requirements for the degree of

MASTER OF SCIENCE

Department of Horticulture

1958

ACKNOWLEDGEMENTS

The author wishes to express his gratitude and thanks to the
many people who have helped with this project. Special thanks are due
Dr. C. E. Peterson for his guidance in planning the project, Dr. E. J.
Benne of the Department of Agricultural Chemistry for his assistance
in the formulation of chemical procedures, Dr. Stanley K. Ries of
the Department of Horticulture, and Dr. G. B. Wilson of the Depart-
ment of Botany, for their suggestions and criticisms, and to the many
others who have given assistance and advice in the completion of this

thesis.

TABLE OF CONTENTS

Page
INTRODUCTION .................... 1
REVIEW OF LITERATURE ............... ' 3
MATERIALS AND METHODS . ............. 8
A. Varieties ................. . 8
B. Sampling .............. . . . . 8
C. Determination of Dry Matter ....... . . 9
D. Determination of Soluble Solids . . . . . . . . . 9

E. Preparation of Samples for Sugar Analyses . . . . 10

F. Determination of Sugars . . . ......... 10
G. Statistical Methods . . . . .......... 16
RESULTS ...................... . 18
A. Dry Matter ................ . 18
B. Soluble Solids ................ 21
C. Sugars ............. 26
DISCUSSION AND CONCLUSIONS ............ . 31
A. Dry Matter .............. .. . . . 31
B. Soluble Solids ................ . 33
C. Sugars .................... 34
SUMMARY ....................... 36

LITERATURE CITED .................. 38

INTRODUCTION

The State of Michigan produced 1700 acres of carrots in 1957 having
a farm value of $1, 034, 000 (1). These figures'do not nearly express the
potential production of carrots in this state, since Michigan has the advan-
tages of suitable climate, large acreages of tillable muck and mineral soils,
and nearness to concentrated populationcenters. In spite of these appar-
ent advantages, the carrot industry is actually declining. Production de-
creased from 2960 acres (average 1949 to 1954), to 1900 acres in 1956,
and further declined to 1700 acres in 1957 (2). At the same time the United
States production remained at approximately 80, 000 acres throughout this
period. What, then, are the reasons for this situation?

The facts are that, at present, Michigan-grown carrots are often
of such poor quality that processors prefer to ship carrots from western
and southern states rather than to use those grown locally. Sweetness and
high dry matter content are two of the most desired features of carrots for
processing. and these traits appear to be generally lacking in Michigan-
grown carrots. Processors and growers in the State are thus keenly inter-
ested in the development of high quality varieties adapted to Michigan con-
ditions, in order to eliminate the need for importing carrots.

As a consequence of these conditions, plant breeders have been en-

couraged to develop varieties of carrots that can compete with southern

and western products on a quality basis. Fortunately, the discovery of
male sterility in the carrot promises a practical means of producing F1
hybrid varieties which are vigorous and more uniform. This may be ac-
complished by bringing together the desired characteristics from selected
inbred lines.

The objectives of this work were to determine the range of varia-
bility in dry matter, soluble solids and sugar content between and within
commercial carrot varieties, and to develop methods for the rapid analysis
of these characteristics as a basis for selection in the breeding program.
This study necessitated a survey of analytical methods for determining
sugars, and modification of these methods specifically for rapid and accur-

ate analysis of dried carrot roots from breeding material.

REVIEW OF LITERATURE

Although studies of sugar and dry matter contents of various plant
varieties and tissues have long been common, analytical work of this type
as applied to selection of carrots has been comparatively recent. The early
work on carrots was primarily concerned with the transformations which
the roots undergo while in storage. Hasselbring (6) found that the principal
changes taking place in carrots during storage were a conversion of sucrose
to reducing sugars and a breakdown of polysaccharides to simple sugars.

He also found that these changes occurred more rapidly at higher tempera-
tures, and that an equilibrium was reached during about the first ten weeks
of storage. Hasselbring further concluded that the flavor of carrots was
determined largely by their natural content of sucrose.

Platenius (12), in the same type of studies, made the interesting
discovery that during the storage period sucrose was converted initially to
reducing sugars, and the process was later reversed; sucrose increased
while reducing sugars‘decreased. This work led Platenius to studies on
the nature of quality in carrots, based on the assumption that quality was
controlled largely by physiological processes.

Since sweetness of the carrot root depends on the relative amounts
of the various sugars present, tests were made by Platenius (13) for their

quantitative identification, based upon the specificity of these sugars on

the time required for osazone formation. His results showed that sucrose
constituted almost all of the disaccharides, while glucose made up almost
entirely the monosaccharide' fraction. Fructose was assumed to be formed
as an intermediate during sucrose hydrolysis and was probably converted
enzymatically to other carbohydrates immediately. Since sucrose is
sweeter than glucose (100 vs. 74. 3 relative sweetness), it was concluded
that the sweetness of carrot roots was dependent on the sucrose fraction

of the total. This supports the theory previously advanced by Hasselbring
(6).

Tenderness of carrot roots was considered by Platenius (13) to be
proportional to the crude fiber content. In his experiments the percentage
of crude fiber remained relatively constant for any given variety harvested
at different physiological ages, indicating an inherent potential for tender-
ness or toughness.

Storage experiments by Platenius (13) showed a rapid increase in
total sugars in stored roots early in the storage period, due primarily to
hydrolysis of polysaccharides. This increase leveled off after about eight
weeks as a result of increased respiration. The percentage of glucose
(reducing sugar) increased until January, and then began to decrease while
the sucrose (non-reducing sugar) percentage decreased until January, and

then began to increase.

Werner( 18) reported that there was a larger amount of sucrose
compared with reducing sugar in both the xylem and phloem regions of the
carrot root throughout the growing season. After about one month of stor-
age the percentage of sucrose in the phloem declined to become less than
that of reducing sugars, probably due to increased respiration. After this
time sucrose again increased in relation to reducing sugars. Werner also

7
reported that the sweetness rating of carrot roots on a basis of 100 for #493”
sucrose and 74 for reducing sugars, was higher in the phloem than in the
xylem throughout the growing season. This condition was probably a re-
sult of the rapid decrease in xylem sweetness during the period of most rapid
root enlargement. Sweetness in both the xylem and the phloem decreased
rapidly in storage until November.

Rygg ( 15) was concerned with the presence or absence of fructose
in carrot roots, since up to this time most investigators, Platenius (13)
among them, had found reducing sugars to be composed largely or entirely
of glucose. His results showed that fructose was present in quantities
closely approaching glucose in Danvers and Imperator varieties stored
fifteen days.

Lipton (7) found that variety, soil type, and maturity of carrots
affected the sugar content. Carrot roots grown on mineral soil contained

31. 3 per cent more sugars on a fresh weight basis than those grown on

muck. He suggested that the lower percentage of sugars in muck-grown

carrots may be a result of excessively high levels of fertility, an off-
balance of nitrogen and potassium, or high soil temperatures. Lipton's

work points out that the best way to express sugar content is on the basis of
fresh weight at time of sampling, since that takes into consideration moisture
content of the root and thus reflects its actual eating quality.

High dry matter is especially desirable in carrot roots used for
processing, since it results in a greater net return per unit weight of raw
product. Werner (18) reported that the dry matter percentages of carrots
fluctuated throughout the growing and storage seasons in the same manner
as the sucrose content. Lipton (‘7) showed that dry matter, as in the case
of sugar content, was affected by soil type, variety and maturity. He
found that dry matter content, although of little value in detecting quality,
was useful in determining how sugars vary in relation to other constituents,
and how changes in water content affect sugar content.

Most of the modern methods for determining sugars are based on
the work of Munson and Walker (11) on methods for analysis of reducing
sugar. Out of their extensive experiments came the conversion tables for
sugars now the official standard for many sugar determinations. Their method
of analysis with some modifications, is recognized by the Association of
Official Agricultural Chemists.

Waldron _e_t a}; (16) in a study of methods, compared Soxhlet extraction

with alcohol and water extraction, acid hydrolysis with invertase hydrolysis,

and the gravimetric and volumetric evaluation procedures. Their results were
generally in good agreement for all methods. However, with some plant mater-
ials, such as spinach and bromegrass, it appeared that some constituents in
plants are more soluble in water than in alcohol, and yield reducing sugars
more readily when hydrolyzed with acid than with invertase. These results
typify the problems likely to be encountered with different methods and different
crops when analyzing for sugars.

The use of the refractometer in determining soluble solids has been
practiced with many crops. Lutz (8) in comparing refractometer readings with
chemically determined sugar contents of several American-type grape varieties,
averaging between 11 and 22 perICent sugar, found differences of 1. 8 to 2. 6 per
cent on a fresh weight basis between the two methods. Webster and Cross (17)
working with grape juice over a four-year period, found a correlation of +. 9247
between total sugars and refractive index values in 208 samples collected from 40
different varieties of grapes. Porter and Bisson (14) using the refractometer to
determine sweetness of watermelons in the field, were able to detect extreme
variations in total soluble solids of individual fruits and also composite samples.
Their results did not prove that significant differences in total sugar content ex-
isted, although fruits with relatively high refractive indices tasted sweeter than
those with low readings. They concluded that variations in soluble solids other
than sugars existed in watermelons. Brown e_t_ El; (3) found a positive correlation
of +. 626‘1‘0. 79 between good taste and high refractive index for eleven lots of dif-

ferent varieties of carrots grown at different nutritional levels and at different locations.

MATERIALS AND METHODS

A. Varieties

Twenty- seven commercial varieties and strains of carrots were
planted in a six-replicate yield trial at the Experimental Muck Farm on May
2, 1957. Eleven of these varieties representing the most common types grown
in the area were selected for analysis. Line MSU 2710 was a single-row 5] of
Long Chantenay selected especially for its sweet taste. These varieties were
field-harvested on September 22, 1957, topped, and ten representative roots
from each of the six replications were packed randomly in wire-bottom crates
in moist sphagnum moss. The roots were stored at 40’F in a common stor—

age until sampling two weeks later.

B. Sampling

Samples for analysis were taken over a period of one week from October
7 to October 13, 1957. Composite samples of the eleven varieties were secured
by selecting fifteen typical roots at random from the variety. These were
washed, dried, and cut into thin (about 1 mm.) slices, amounting to approxi-
mately 10 grams from each root, to give a total fresh sample of 150. 0 grams
per variety. Three of the varieties were sampled at top, middle and bottom
of the roots to determine if significant differences in sugar content existed

in different parts of the root. All sampling techniques in these experiments

were guided by the necessity of saving as much of each carrot root as possible,
so the remnant could be planted for genetic studies and breeding.

Since it was desirable to find single roots high in dry matter and sugar
content for breeding purposes, roots of each variety were sampled individually
for analysis. Fifteen typical roots were selected at random, washed to re-
move clinging soil, dried, and sampled. The lower one-half inch of the roots
was discarded and approximately 35 grams from the middle portion of each root
were cut into thin slices. Sampled roots were tagged and returned to storage

until planting in the greenhouse.

C. Determination of Dry Matter

 

Samples were weighed into tared aluminum foil boats and dried im-
mediately at 160° to 170’F in a hot air drying oven for approximately 36 hours
before reweighing. No carmelization of sugars was observed under these con-
ditions. Drying was continued until a number of the samples had come to
constant weight, at which time they were removed from the oven, allowed to
cool a few minutes at room temperature, and weighed to the nearest 0. 1 gram.
Per cent dry matter was determined by the formula:

Grams Dry Weight
Grams Fresh Weight

 

x 100 = Per Cent Dry Matter

D. Determination of Soluble Solids

 

Samples for refractometer analysis were taken by slicing two sections

lO.

frOm the carrot root immediately above those removed for sugar analysis.
These were sealed immediately in Saran Wrap to prevent moisture loss, label-
ed, and frozen at -4°F until analyzed.

Samples were removed from the freezer approximately three to four
hours before analysis and allowed to come to room temperature. Any moist-
ure condensed on the outside of the wrap was carefully blotted off. The freez-
ing process had softened the tissue sufficiently so that juice could be easily
squeezed out by hand. A Bausch and Lomb hand refractometer was used for
the analyses, and readings were estimated to the nearest 0. 1 per cent. No
differences were found in comparing free-run juice with that squeezed out by
hand in any given sample. Results are given in per cent total soluble solids

expressed as sucrose.

E. Preparation of Samples for Sugar Analyses

 

After the samples were thoroughly dried and weighed, they were ground
in a semi-micro Wiley mill through a 20-mesh screen. The mill was thorough—
ly cleaned by compressed air between samples. The dried samples were
ground into labelled two-ounce bottles, mixed thoroughly, and stored until

analyzed.

F. Determination of Sugars

 

Since difficulties may arise in attempting to use standard analytical

11.

procedures on materials of diverse natures, it was necessary to prove the
suitability of known procedures for analyzing dried carrot roots. Further-
more, since the ultimate purpose of these studies was to permit a comparison
of the sugar content of one carrot root with another for selection purposes, a
high degree of precision was not required. Attempts were made, therefore,
to develop a procedure which would permit making rapid determinations with
reasonable precision. The results obtained by the A. O. A. C. method for the
determination of sugars were assumed to be the true values for sugar content
in the-roots and were used as the basis of comparison in this work.

Based on the results of Waldron gt a}: (16), water-extraction pro-
cedure for removing sugars from the tissue, and a hydrolyséériod of
fifteen minutes in a bath of boiling water were selected for this work. With
this modified method it was possible to carry out the entire procedure in one
day. Thefihlings reduction of copper gravimetric technique was chosen for
the actual determination of sugars, since Waldron e_t a}; (16) showed this
procedure to be comparable in precision to the volumetric method.

In an attempt to further simplify the procedure, a number of analyses
were made on the same sample with and without the use of lead acetate, which
is used to remove proteins and other interfering substances. These analyses

showed that, in the case of dried carrot material, the use of lead acetate did

not significantly change results when using the modified method developed in

12.

these studies (see Table I). These results agreed with those of MacGillivray
$3131; (9) on tomatoes, and Morris _e_t _a_l_. (10) on grains and other field crops.
This phenomenon may result from a lack of interfering substances in certain
types of tissue.

Since in almost all cases the value for total sugars determined by the
modified method were higher than those determined by the A. O. A. C. method,
an attempt was made to discover the cause of these differences. Determina-
tions on the same samples by the A. O. A. C. method, but substituting a fifteen-
minute boiling water bath hydrolysis gave values closer to those determined
by the A. O. A. C. method than to the modified method. This indicated that
the larger values obtained by the modified method were probably a result of
the greater solubility of sugars in water as opposed to the alcohol extraction
in the A. O. A. C. method. These results conform with those of Waldron _e_t_ _a_l_.
(16) mentioned previously.

Since it seemed desirable to determine reducing and non-reducing
sugars, as well as total sugars, procedures were also adapted for these deter—
miriations. All methods are outlined below:

Total Sugars

 

l. Weigh out 1 gram samples of dried material into 100 m1. volumetric
flasks.
2. Place 30 ml. No. 10 Selas crucibles into 105°C oven, allow to dry at

least 3 hours, cool 20 minutes in dessicator, and weigh.

TABLE I

Values for Total Sugars in a Sample of Dried Carrot Roots as Determined
by the A. O. A. C. and Modified Methods

 

1/

 

Method Cleared’ Average Not Cleared Average
A. O. A. C. Method 37. 59 39. 56
37. 16 39. 40
(Hydrolyzed\dvernight 37.44 38. 98
at room temperature) 38. 66
“ 38. 35 37. 84 39. 31
A. O. A. C. Method 39. 65 39. 80
39. 95 39. 80 40. 03 39. 92
(Hydrolyze minutes
in boilingfili§ bath)
Modified Method 39. 71 40. 08
37. 27 40. 55
40. 53 41. 64
41. 20 42. 10
41. 75 42. 63
43. 18 41. 90
42. 63 41. 78
42. 70 41. 13 41. 34 41. 50

 

1/

Cleared with lead acetate.

Excess lead removed with potassium oxalate.

l4.

3. Add 50 ml. distilled water to samples, place on hotplate at 98°C
for 30 minutes.

/ 4. At the same time set up blank determination of 50 ml. distilled

\

water in 100 ml. flask. o
If") .1“ 31.9. I will "‘1. if 1063 FIT“?
5. Allow to cool, make to volume, and filter through dry Whatman No.

(Sudan? I“ ‘
"In 42 quantitative filter paper into 25 ml. Erlenmeyer flasks.
lit - , . .
(2)“ Wk" “.
N‘DPCF‘ 6.,I’I’ipette out 40 mls. into 100 ml. volumetric flasks. Add 2 ml.

concentrated HCl and hydrolyze in boiling water bath for 15 minutes.
7/. Cool, almost neutralize the HCl with 40 per cent NaOH solution,
and make to volume.
8. Filter through dry Whatman No. 42 filter paper into 50 m1. volu-
metric flasks to mark, and transfer to 400 ml. beakers.
9. Add 25 ml. each of alkaline sodium potassium tartrate solution and

CuSO46H20 solution simultaneousm

 

10. Cover with ribbed watch glass, bring to boil in exactly 4 minutes,
and boil for exactly 2 minutes.

11. Filter into a tared Selas crucibles; with suction. Wash well with
hot distilled water.

12. Dry at least 3 hours at 105'C in a hot air oven, cool in dessicator

20 minutes, and weigh.

15.

13. Calculate per cent invert sugars from Munson and Walker tables.
Sample calculation:

1 gram x 40 m1. x 50 ml.

= 0.2 1' t
100 ml. 100 ml. gram/a Iquo

 

To the grams of Cu 0 determined by weight, subtract the grams of CuZO

2
in the blank.

For example: Grams Cu20 = .1642 Blank == . 0003
Grams - Blank = . 1639 grams 2 163. 9 mg.

Look up values in tables under invert sugar.

162 mg. Cu20 = 73. 9 mg. invert sugar
163. 9 mg. Cu20 = x mg. " "
164 mg. Cu20 z 74. 9 mg. " "

Thus, by interpolation

L2 3 x
2.0 iTE)‘
2x = l. 9
x = . 95 73. 9 mg.

. 95 mg.
74. 85 mg. or . 07485 gm invert sugar/. 2 g. aliq.

For a 1 gm. sample: . 07485 x 100 = 37. 43% invert sugar
. 2

Reducing Sugars

 

The procedure for determining reducing sugars is essentially the

same as for total sugars, except that hydrolysis is omitted.

16.

Steps 1, 2, 3, 4 and 5 - Same as for total sugars.

6. Pipette out 20 ml. aliquot directly into 400 ml. beaker. Add 30 ml.
distilled water. Proceed to step 9.

9, 10, 11, 12. Same as for total sugars.

13. Since only a 20 ml. aliquot was used, the calculations are:

1 gm. KM: = 0.2 /ali not
100 ml. gm q

Thus, the remaining calculations are identical to those for total sugars.
To determine the per cent sugars on the basis of fresh weight, the calculations
are:

Per cent sugars == (Vlinvert sugars/ dry wt.) x (%dry matter)
100

Non-reducing Sugars

 

Since total sugars consist of reducing plus non-reducing sugars, the

non-reducing sugar content was obtained by difference.

G. Statistical Methods

 

The results of all individual-root determinations were analyzed by
analysis of variance. Significance between varieties for dry matter, soluble
solids, and reducing sugars was tested by the multiple range test, as outlined
by Duncan (4). No difference was considered significant unless it exceeded

the 1 per cent level.

17.

For each variety analyzed on an individual root basis the mean ()2),
standard deviation (Si), standard error (S. E. i), and coefficient of varia-
tion (C. V.) were calculated. Regression lines and correlation coefficients
were computed to show the relationships between soluble solids and dry

matter content and between soluble solids and total sugar content.

18.

RESULTS

A. Dr; Matter

 

Dry matter values for composite samples of the eleven varieties and
strains of carrots used in these experiments are shown in Table II. Imperator
Lot 1027 was highest in dry matter content with 10. 8 per centl/ and MSU 2710
was lowest with 8. 5 per cent. In the three varieties which were sampled in
different areas of the root, the dry matter percentage was in all cases high-
est near the top, intermediate in the middle, and lowest in the bottom portion
of the root.

Dry matter contents of iWof the eleven varieties
and strains are given in Table IIL The variety with the highest dry matter
content was Imperator Lot 1027, with a mean of 10. 60 per cent, and the low-
est was MSU 2710 with 8. 22 per cent. The greatest variability in dry matter
content within a variety was in Chantenay Lot 1021, which had a range of
from 7. 7 to 13. 3 per cent. The least variability was in MSU 2710, which
ranged from 7. 1 per cent to 9. 1 per cent dry matter. Coefficients of varia-
tion of the variety means ranged from a high of 14. 3 per cent in Chantenay
Lot 1021 to a low of 7. 1 per cent in Imperator-Lot 1016. The coefficient of
variation for all samples in these experiments was 9. 8 per cent. The dry

matter determinations for eleven varieties were analyzed statistically, and

-1-/ In these varieties in which composite samples were analyzed in three areas
of the root, the values determined for the middle portion were chosen as most
nearly comparable to those for the other varieties.

TABLE 11

Values for Sugars and Dry Matter in
Expressed as Per Cent of the Fresh Weight at Time of Sampling

osit Samples of Carrots,

 

 

, _ Root Total Reducing Non-Reducing Dry

Lot NO' Variety or Strain Portion Sugars Sugars Sugars Matter
1002 Experimental Middle 4. 02 1. 28 2. 74 9. 5
1007 Experimental Middle 4. 17 0. 86 3. 30 10. 0
1015 R. C. Chantenay Top 3. 57 0. 58 2. 99 9. 3
" Middle 3. 39 0. 70 2. 69 8. 9
" Bottom 3. 35 0. 90 2. 45 8. 6
1016 Imperator L. T. Middle 3. 58 0. 79 2. 79 9. 4
1017 Gold Spike Top 3. 19 0. 49 2. 71 9. 2
" Middle 3. 22 0. 96 2. 26 8. 9
" Bottom 2. 96 0. 80 2. l6 8. 7
1018 Gold Pak Middle 3. 76 0. 65 3. 11 9. 9
1021 Chantenay Middle 3. 76 1. 08 2. 68 8. 7
1022 Waltham Hicolor Middle 3. 51 O. 69 2. 82 8. 9
1027 Imperator L. T. Top 4. 50 0. 39 4. ll 10. 9
" Middle 4. 72 0. 52 4. 20 10. 8
" Bottom 4. 75 0. 70 4. 05 10. 7
747 MSU 2710 S1 Middle 3. 18 O. 81 2. 37 8. 5
1011 Nantes Middle 3. 82 l. 25 2. 57 9. l

 

l9.

TABLE III

Dry Matter Content of Carrot Varieties and Strains, Expressed as Per Cent of Fresh Weight at Time of Sampling

 

 

1021 1011 747 10221/ 1027-y

Lot Number of Variety or Strain
1017 1018

1016

1007 1015

1002

Root No.

 

9. 9
10. 5

9.2

9.6 7.2

12. 0 10. 5

8.9

10. l

8.0
9.1

9.7

10. 0

8.7

10. 3 9. 4 9. 4 8. 5 9. 8

9.1

9.4

8. 9
10. 2

10. 4

8.2

8. 3 8. 6 10. 5 9. 3 9.9 9. 0
10. 4 . 13. 3

7.2

9.0

11.5
~12.4

8.3 9.7

8.7

10. 0

8.6

9.7 8.4

8.0

9. 0 8. 2 10. 0 7. 5 8. 8 10. 1 9. 3 7. 8 9. 7
10. 3

8.8
11.1

10. 9

9.2

7.9

8. 5 9. 8 8. 5 8. 7
10. 2 10. 3

9.9

9. 2
10. 9

10. l

9.9

8.6

7.7

9.0

8.6

10. 6

9.6
10.3

10. 3

9.1 9.5 8.5 9.4 8.9 7.2 9.3
10. 2

8.8

10. 7

9. 4
10. 7

7. 4
10.2

8.5

8.4
12.4

9.7 8.9

10. 5

8.2

9.7 8.2

8.7

8.7

9.4

9. 5
10. 4

9. 0
10. 6

7.9

9. 7
12. 6

9.4
10.4

10
11
12
13
l4
15

8.7 8.8 7.1

9. 1
10. 5

8.5

9.1

9.1

8.5

9. 4 8. 5 9. 5 8. 9
12. 0

8.7

8.6 9.7 9.3 11.0 8.3 9.3 8.4
'7.3 10.1

9. 5
10.2

8.6

9.4

9.7

9. 9
10. 4

9.8

10. 6

9.9 8.4 7.7 8.6

9.9

10. 5 9. 3

10.0

 

10. 60

10. 23 8. 70 9. 68 8. 88 10. 03 9. 35 9. 33 8. 22 9. 26

9. 50

Mean (12)

i0. 84

10. 64 £0. 86

‘11. 06

‘10. 87 '1'1. 34

I0. 83

to. 69

1'0. 89

+1. 00

+0. 86

'X
U)

‘30. 26

0. 27

to. 17 f

o. 23 to. 35 +0. 27

+

+0. 21

0. 18

+

0. 23

+

+0. 26

“1‘0. 22

5.3.,-(

7. 9%

9.8% 10.2% 7.1% 9.3% 8.7% 14.3% 11.4% 7.8% 9.3%

9.1%

C. V.

 

 

1/ Only 10 samples available.

20.

21.

the results of a multiple range test are presented in Table IV.

Since one objective of this study was to develop rapid and efficient
means of selection for dry matter and sugar content, the relationship between
soluble solids, as determined by the refractometer, and dry matter content
was investigated. A highly significant correlation coefficient of +0. 816 was
found between refractometer reading and dry matter percentage. A similar
relationship has been previously determined for onions by Foskett and
Peterson (5).

A regression of dry matter on soluble solids (Figure 1) showed a
standard deviation from the regression line of I0. 454 per cent, indicating
that the dry matter content of carrot roots can be predicted with a reason-

able degree of accuracy from the refractometer reading.

B. Soluble Solids

 

The results of refractometer analyses of individual root samples of
the eleven varieties and strains of carrot roots are given in Table V. The
variety means varied from 6. 1 to 7. 2 per cent soluble solids. The multiple ~
range test is presented in Table VL In general, the Chantenay types con-
tained the lowest percentages of soluble solids, with Gold Spike, Nantes.
Waltham Hicolor, and Gold Pak intermediate. Imperator and the experi-
mental types were highest in the range.

In soluble solids, roots of Red-cored Chantenay Lot 1015 varied from

TABLE IV

Multiple Range Test for Significance of Per Cent Dry Matter
Between Carrot Varieties and Strains

 

 

 

 

 

 

Variety. Lot Mean Stan-V
or Strain Number Sig.
MSU 2710 747 8. 22
Red- cored Chant. 1015 8. 70
Gold Spike 1017 8. 88 l
Waltham Hicolor 1022 9. 26
Nantes 1011 9. 33
Chantenay 1021 9. 35
Experimental 1002 9. 50
Imperator 1016 9. 68 l

- Gold Pak 1018 10-03
Experimental 1007 10. 23 I

_ Imperator 1027 10. 60

Coefficient of Variation = 9.8%

S. E. i = ‘10. 074%

 

— *— :-——<_
I __ _'

 

1
-/Means not spanned by a continuous line differ at the 1% level;
e. g. , the mean 9. 26 differs from 8. 88, but not from 9. 33, etc.

22.

23.

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TABLE V

1/

Soluble Solids of Carrot Varieties and Strains, Expressed as Per Cent Sucrose-

 

Lot Number of Variety or Strain

10273/

10222/

747

1007 1015 1016 1017 1018 1021 1011

1002

Root No.

 

6.5

6.0

7.0 6.0

“8.5 6.8

7.0
6.8

6.5 6.0 8.0

6.5

7.4

6.9

6.9

7.0

6.1

7.0

6.0 7.0 6.5

7.0

7.0
8.2

6.0

6.9

7.5

7.0 6.8

6.5

6.0 4.5 6.2

8.0

7.0 6.3 6.7

7.0 7.0

6.5

7.0 6.5 7.1

6.0

8.5

6.9

6.0

7.0

5.8 7.3

5.9

6.0 6.0 7.1

6.5

8.0
7.5

6.0

5.9

6.0

6.2 6.4

6.5

7.5 6.5 7.5

8.0
7.5

6.5 7.4

8.0
6.5

8.0 6.0 6.5 6.3 5.8
6.0

8.0

7.0

7.0

5.1

5.9 6.8

6.9

6.5

7.5

7.5

6.8

5.6

6.0

6.0

6.5 6.0 7.2 6.0 6.9 6.8

6.5

7.5

7.6

6.2

8.5

_II1

7.0 7.5 5.8 7.0 6.9 7.2

10
11
12
13
14
15

O

\0

w
o

\O

O
o

\0

l0

06.

O

\O

O

O\

O

\O

6.0

H
O

[x

I!)
o

0

00
O
h-

I!)

I!)

O

[s

6.0

6.5

7.5 6.0

7.0

7.0

5.0

8.0
7.0
7.5

7.0
7.5

7.5 5.6 7.0 7.5 6.5 6.1

6.0

6.0 6. 1

5.5

7.0

7.2

7.5

6.5

7.5

 

7.4

7.1 6.1 7.2 6.5 6.9 6.4 6.8 6.1 6.6

7.1

Mean (5;)

+0. 6

21:0. 7

t0. 5

to. 8
+

‘10. 7 to. 6

t0. 5

‘10. 7

to. 8
+

to. 9

’50. 7

‘1‘0. 2

t0. 1 to. 2

0.2

t0.2 10.2 0.2 t0.2 t0.1 t0.2 t0.2

S.E.i
C. V.

8%

10% 9% 12% 8% 11%

8%

13% 13% 10%

10%

 

l/As determined by Bausch and Lomb hand refractometer.

24.

—2—/ Only 10 samples available.

25.

TABLE VI

Multiple Range Test for Significance of Per Cent Soluble Solids-U
Between Carrot Varieties and Strains

 

 

 

 

Variety Lot Mean Stanz/
or Strain Number Sig.
MSU 2710 747 6. 1

Red- cored Chantenay 1015 6. 1 I
Chantenay 1021 6. 4

Gold Spike 1017 6. 5
Waltham Hicolor ‘ 1022 6. 6
Nantes 1011 6. 8 I
Gold Pak 1018 6. 9 I
Experimental 1002 7. 1
Experimental 1007 7. l
Imperator 1016 7. 2
Imperator 1027 i 7. 4 I

Coefficient _of Variation = 10. 1%

5. E1? = to. 055%

1
“/As determined by Bausch and Lomb hand refractometer.

2
r/Means not spanned by a continuous line differ at the 1% level,

e. g., the mean 6. 4 differs from 6. l, but not from 6. 5.

26.

4. 5 to 8. 0 per cent. Gold Spike Lot 1017, the least variable, ranged from
5. 6 to 7. 2 per cent. MSU 2710 also showed a small amount of variability,
ranging from 5. l to 6. 9 per cent soluble solids. The coefficient of variation
for the total population was 10. 1 per cent.

The extremes for soluble solids in these experiments were 4. 5 per
cent in a root of Red-cored Chantenay and 9. 0 per cent in a root from Experi-
mental Lot 1007. This range does not represent the maximum, however,
since refractometer readings on 400 individual carrot roots selected in the
breeding project at Michigan State University ranged from 4. 5 to 11. 0 per

cent soluble solids.

C. Sugars

The values obtained for the determination of sugars in composite
samples of eleven varieties and strains of carrot roots are given in Table IL
Varieties ranged between 3. 18 and 4. 72 per cent total sugars, 0. 52 and 1. 28
per cent reducing sugars, and 2. 26 and 4. 20 per cent non-reducing sugars
among the tested varieties.

Four of these varieties were analyzed for sugars on an individual root
basis and the results are summarized in Table VII. Variety means for total
sugars ranged from 3. 83 per cent in Imperator Lot 1027 to 3. 33 per cent in
Gold Pak Lot 1018, and individual root extremes were 6. 41 per cent in a

root of Nantes and 1. 92 per cent in a root from Gold Pak. There was no

27.

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28.

difference in total sugar content between varieties. However, Nantes Lot

1011 showed a greater coefficient of variation than the other three varieties

for total sugars. The least variability was observed in Imperator Lot 1027.
The coefficient of variation for all samples collectively was 23 per cent.

A regression of total sugars soluble solids showed a standard deviation from
the regression line of “1’0. 546 per cent. The correlation coefficient of +0. 751
(Figure 2), indicates that total sugars can be estimated from the refractometer
reading. '

Reducing sugar content determined from composite samples 'of all
eleven varieties ranged from 0. 52 to l. 28 per cent. Individual root samples
of the four varieties showed extremes in reducing sugars ranging from 0. 00
per cent in a root of Gold Pak to 1. 65 per cent in a root of Nantes. The
multiple range test for reducing sugars is presented in Table VIII. The
most variable variety in reducing sugar content was Gold Pak, with a coeffi-
cient of variation of 97. 0 per cent. The least variable was Nantes, with a
coefficient of 42. 7 per cent (Table VII). The coefficient of variation for all
samples was 55. 5 per cent.

In single roots of Nantes, the most variable of the four varieties sampled,
non-reducing sugars ranged from a high value of S. 74 to a low of 1. l9 per cent.
Imperator Lot 1027 was the least variable in non-reducing sugars, showing a
coefficient of variation of 20. l per cent as compared to 42. 2 per cent for Nantes.

The coefficient of variation for all samples was 30. 7 per cent.

29.

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30.

TABLE VIII

Multiple Range Test for Significance of Per Cent Reducing Sugars
Between Carrot Varieties and Strains

 

 

Variety Lot Number Mean ::;.l/
Gold Pak . 1018 0. 29
Imperator 1016 O. 54
Imperator 1027 0. 64
Nantes 101 l 0. 82

Coefficient of Variation = 55. 5%

s.E._=t.043%
X ,

 

 

1/
"' Means not spanned by a continuous line differ significantly;

e. g. , 0. 54 differs from 0. 29, but not from O. 64.

31.

DISCUSSION AND CONCLUSIONS

A. Dry Matter

 

Dry matter content of a number of composite samples of carrot varie-
ties ranged from 8. 5 to 10. 8 per cent. The varieties having the lowest per-
centage dry matter were the Chantenay strains, primarily used for process-
ing, while Nantes, Waltham Hicolor, and Imperator Lot 1016 were inter-
mediate. Two market types, Imperator Lot 1027 and Gold Pak, and the ex-
perimental strains were highest. Some of the market types were high in dry
matter and some processing types were low. This is the reverse of what
would be expected, since processing carrots should be high in dry matter
to increase net yield of the processed product and market types should be
succulent.

The means of individual root analyses for most of the eleven varie-
ties and strains of carrots approximated the values obtained for the composite
samples, indicating that the sampling techniques for the two different deter-
minations were comparable. The extremes in dry matter content of 13. 3
and 7. 1 per cent are important to the plant breeder because they indicate
the levels of dry matter content that can be achieved through inbreeding
and hybridization. The fact that in these experiments the least variable
variety in dry matter content was MSU 2710, an S1 inbred, shows that uni-

formity can be improved by inbreeding.

32.

In the three varieties analyzed at top, middle, and bottom of the root,
the dry matter percentages in all cases were highest in the top, intermediate
in the middle, and lowest in the bottom portion of the roots. This might be
expected in the mature root, since the upper portions of the carrot contain
a higher percentage of differentiated cells than the lower portions.

Differences in dry matter were observed between varieties. Although
not analyzed by replications as such, samples of all varieties except MSU
2710 were taken at random from a six-replicate yield trial. The variation
between varieties indicates that definite genetic differences exist in dry
matter content.

The correlation coefficient of +0. 816 between dry matter and soluble
solids shows that as soluble solids increase there is a proportional increase
in dry matter. The regression line computed for these factors demonstrates
that, through the use of the refractometer, dry matter content of carrot
roots can be estimated with an acceptable degree of accuracy from the stand-
point of making selections in a breeding program. Actual dry matter content
can be estimated by using the regression formula presented in Figure 1.
Large numbers of samples can thus be rapidly analyzed with the refracto-

meter, rather than by the slower process of determining dry matter content

by weighing.

33.

B. Soluble Solids

 

Variety means varied from 6. l to 7. 2 per cent, a difference of only
1. l per cent. These data would seem to put limitations of the effectiveness
of the hand refractometer used in these experiments, since readings could
be estimated only to the nearest 0. l per cent. However, means differing
by as little as O. 2 per cent were significant at the l per cent level of proba-
bility.

Variability ranges up to only 3. 0 per cent within varieties might sug-
gest that total soluble solids do not vary as greatly as dry matter content in
carrot roots. By comparing the Coefficients of variation for the two, how-
ever, it is evident that the variability is approximately the same. Variety
means also ranked in about the same order for total soluble solids as they
did for dry matter content.

For the plant breeder the extreme readings for individual roots of 4. 5
to 9. 0 per cent soluble solids are important, becau:e with thi- ran-Te of varia-
bility it is possible to develop uniformly high or uniformly low lines by means
of inbreeding and selection. In an assortment of inbred lines and open pollin-
ated selections used in the carrot breeding project at Michigan State Univer-
sity refractometer readings were observed up to 11. 0 per cent soluble solids.
Such high values present the possibility of developing varieties having soluble
solids and dry matter content higher than any now available, simply by working

with selections from present varieties.

34.

C. Sugrs

The sugar determinations for composite samples of carrots show
that reducing sugars comprise a small fraction of the total sugar content;
in most cases less than one-fifth. The means of the four varieties analyzed
for total sugars did not differ. This might lead one to the conclusion that
little genetic variability exists between varieties. However, as evidenced
by the relatively high standard deviations of each of the varieties, this
conclusion would be misleading.

The extreme ranges of 6. 41 and l. 92 per cent total sugars point out
the possibility of obtaining varieties with total sugar content at, or even ex-

ceeding, these extremes. The correlation coefficient and regression of total
sugars on soluble solids shows that total sugar content, as well as dry matter.
can be estimated from the refractometer reading by using the regression
formula.

Reducing sugars were more variable both between and within varieties
as compared to total and non-reducing sugars. Although some of the varia—
bility is undoubtedly genetic in nature, the difficulties in duplicating results
experienced with some samples would seem to be of a technical nature.
Probably most of the observed variability in reducing sugar content between
varieties was due to laboratory techniques rather than to genetic factors.

The fact that Nantes, the variety varying most in total sugar content, was

35.

the least variable in reducing sugars suggests that some varieties were more
susceptible to these laboratory errors than others.

Non-reducing sugars followed the same pattern as total sugars in the
four varieties analyzed. This might be expected since non-reducing sugars
constitute by far the greatest fraction of the total sugar content. The higher
coefficient of variation for non-reducing sugars than for total sugars is prob-
ably due to calculating non—reducing sugar content by subtracting reducing
sugars from total sugars, thus reflecting the great amount of unexplainable
variation in reducing sugar content.

A comparison of sugar determinations shows that agreement was not
good in all cases between composite samples and the means of individual root
samples. Since all sugar analyses were duplicated and precision was in most
cases 0. 5 per cent on the basis of the dry weight samples, there seems to be
no good explanation for this discrepancy. One possibility is that sampling
error in the analysis of composite samples was high and in the same direction
as the error in precision, resulting in the generally lower mean values based

on individual root samples.

36.

' SUMMARY

The objectives of this study were to determine the range of variability
in dry matter and sugar contents within and between varieties of carrots, and
to develop methods for rapid analysis of these constituents for selection pur-
poses. This necessitated a study of methods for sugar determination and
modification of these methods specifically for the dried carrot roots used in
this experiment.

Dry matter analyses showed extremes between varietal means of 10. 8
per cent for Imperator Lot 1027 and 8. 5 per cent for MSU 2710. Within a
single variety, roots of Chantenay Lot 1021 varied from 7. 7 per cent to 13. 3
per cent dry matte r. The extremes observed for single roots were 13. 3
per cent in a root of Chantenay, and 7. 1 per cent in a root of MSU 2710.
Soluble solids, as determined by the refractometer, varied from a mean
of 7. 4 per cent in Imperator Lot 1027 to 6. 1 in MSU 2710. The greatest
variability in soluble solids for a single variety occurred in Red-cored
Chantenay, roots of which ranged from 4. 5 to 8. 0 per cent. Individual-root
extremes were 9. 0 per cent in Experimental Lot 1007, and 4. 5 per cent in
Red-cored Chantenay. Among varieties, total sugar content varied from
4. 72 per cent in a composite sample of Imperator Lot 1027 to 3. 18 per cent
in a similar sample from MSU 2710. Within varieties the greatest varia-

bility was in Nantes Lot 1011, roots of which ranged from 2. 23 to 6. 41

37.

per cent total sugars. The extremes observed for individual roots in these
experiments were a high of 6. 41 per cent total sugar in a root of Nantes and
a low of 1. 92 in a root from the variety Gold Pak. Reducing sugars were
extremely variable, both within and between varieties. Non-reducing sugars
followed closely in the pattern of total sugars and did not differ significantly
between varieties.

Dry matter and total sugar content were correlated with soluble
solids as determined by the refractometer. Regressions computed from
these data demonstrate that, by means of the refractometer, both dry
matter and total sugars can beestimated with a degree of accuracy that

is satisfactory for root selection in a breeding program.

10.

ll.

38.

LITERATURE CITED

Agricultural Marketing Service. 1957. U. S. D. A. Michigan commercial
' vegetable statistics.

Agricultural Statistics. 1956. U. S. D. A. Supplement.

Brown, H. D., M. K. Miller, K. Alban, R. Short, R. Schulkers, and
C. Murname. 1944. Carotene, flavor, color, and refractive in-
dices of carrots grown at different fertility levels. Proc. Amer.
Soc. Hort. Sci. 44: 465-467..

Duncan, D. B. 1955. Multiple range and multiple F tests. Biometrics
11: l.

Foskett, R. L., and C. E. Peterson. 1950. Relation of dry matter
content to storage quality in some onion varieties and hybrids.
Proc. Amer. Soc. Hort. Sci. 55:314-318.

Hasselbring, H. 1927. Carbohydrate transformation in carrots during
storage. Plant Physiol. 2: 225-243.

Lipton, W. J. 1953. Sugar and carotene contents of carrots as in—
fluenced by variety, soil type, and storage. Thesis for M. S.
degree, Mich. State Univ.

. Lutz, J. M. 1938. Factors influencing the quality of American grapes

in storage. U. S. D.A. Tech. 3111. No. 606.

MacGillivray, J. H. , and A. H. Watson. 1929. Studies of tomato quality.
V. Clearing is not essential in determining reducing sugars of ripe
tomato fruit extract. Proc. Amer. Soc. Hort. Sci. 26: 137-138.

Morris, V. H., and F. A. Welton. 1926. Importance of clearing hydro-
lyzed solution in the determination of acid-hydrolyzable carbohydrates
in green plant tissue. Jour. Agr. Res. 33: 195-199.

Munson, L. S., and P. H. Walker. 1906. The unification of reducing
sugar methods. Jour. Amer. Chem. Soc. 28 (6): 663-686.

39.

12. Platenius, Hans. 1932. Chemical changes in carrots during storage.
Proc. Amer. Soc. Hort. Sci. 29: 450 (Abstract).

13. . 1934. Physiological and chemical changes in carrots
during growth and storage. Cornell Univ. Agr. Exp. Sta. Memoirs
161.

 

14. Porter, D. R., and C. S. Bisson. 1934. Total soluble solids and
sugars in watermelons. Proc. Amer. Soc. Hort. Sci. 32: 596-599.

15. Rygg, G. L. 1945. Sugars in the root of the carrot. Plant Physiol.
20: 47-50.

16. Waldron, D. R., c. D. Ball, E. J. Miller, and E. J. Benne. 194.3:-
A study of methods for the determination of sugar in crop plants.
Jour. of Assoc. of Off. Agric. Chemists.

17. Webster, J. E., and F. B. Cross. 1935. Use of the refractometer in
studying sugar content of grape juices. Proc. Amer. Soc. Hort.
Sci. 33: 444-446.

18. Werner, H. O. 1941. Dry matter, sugar, and carotene content of
morphological parts of carrots through the growing and storage
season. Proc. Amer. Soc. Hort. Sci. 38: 267-272.

1‘ 3
m1