Solanum (2n = 2x = 24) species (Solanum chacoense) when used as male self-compatible donor can be easily hybridized with other wild species (2n = 2x = 24) and dihaploids of Solanum tuberosum (2n = 4x = 48). Previous work carried out using diploid breeding techniques has had success and this has culminated into potato breeding platforms that exploit the 2n gamete breeding scheme with a focus on creating genetic diversity. In a diploid breeding program, the spontaneous occurrence of tetraploid progeny complicates the breeding process. Thirty-five 2x x 2x crosses were made to examine spontaneous incidences of tetraploid progeny in the F1 hybrid progeny of 2x x 2x S. tuberosum dihaploids by self-compatible donors S. chacoense (M6) and DRH S6-10-4P17. In these 2x x 2x crosses we expect both diploid and tetraploid progeny. Results showed that by using chloroplast counting and SNP genotyping, the frequency of tetraploid progeny ranged from 0 to 40% in the 35 crosses between Atlantic or Superior dihaploids to self-compatibility donors. This result is attributed to bilateral sexual polyploidization (BSP) which is the result of 2n egg and pollen formation. The results of this study will inform breeders developing diploid germplasm the potential consequences of 2x x 2x crosses between Solanum species and dihaploids of S. tuberosum.Bacterial wilt, caused by Ralstonia solanacearum (Rs), is a major disease in most tropical, subtropical and temperate potato producing regions of the world. Breeding for bacterial wilt disease resistance in potatoes is challenging due to the pathogen's aggressive nature and persistence in the environment. Accessions of S. commersonii are known to harbor resistance, therefore, breeding for genetic resistance to bacterial wilt may be an effective strategy to control bacterial disease. The genetic variation among S1 selfed progeny of S. commersonii line MSEE912-08 was characterized by artificially inoculating them with an isolate of Rs. One hundred and twenty individual S1 selfed progeny were screened for Rs resistance by artificial inoculation with Rs isolate NAK66 in a glasshouse replicating each line three times in the experiment. Percent disease reaction was calculated as the relative area under disease progress curve (RAUDPC). RAUDPC was fitted to a random effects mixed model and the means were transformed as a Best linear unbiased prediction (BLUP) score for each clone. BLUP values ranged from -19.25 for the most resistant to16.83 for the most susceptible clones. Genotyping S1 individuals using the V3 Illumina Infinium Array generated 117 polymorphic single nucleotide polymorphic (SNP) markers from the selfed population. Using 98 of the 120 progeny the significance of the markers was confirmed by single marker analysis from WindowsQTLCartographer 2.5, as well as a single marker ANOVA test using JMP®, Pro13. Significant markers were identified on Chromosome 4 which explained 9.8% to 13% of the phenotypic variation. SNP markers identified resistance associated with a homozygous genotype. Specifically, the genotypic value prediction from BLUP scores in single marker ANOVA showed that the homozygous genotype of the SNP markers in solcap_snp_c2_35970, PotVar0015326, PotVar0075537, solcap_snp_c1_10181, solcap_snp_c1_4109 and solcap_snp_c2_12904 were significantly associated with Rs resistance. This study was able to discover self-compatibility in S. commersonii. This study provides potential germplasm that can be used in marker assisted breeding in potato. Secondly, self-compatibility was identified in S. commersonii and should be further evaluated for use in a diploid breeding program.
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