Marker-assisted selection in segregating populations of tomatoes for resistance to TYLCV, ToMV, and Fusarium wilt

Tomato yellow leaf curl virus (TYLCV), tomato mosaic virus (ToMV), and Fusarium wilt are three of tomatoes' most important viral and fungal diseases.

In this study, the application of molecular markers associated with tomato yellow leaf curl virus resistance gene (Ty1), tomato mosaic virus resistance gene (Tm2), and Fusarium wilt resistance gene (I-1) (linked marker) were evaluated. In order to optimize and use SNP markers (by HRM diagnostic method) and SCAR markers, segregating populations of tomatoes were produced by self-pollination of commercial hybrid cultivars. For Ty1 and Tm2, a part of the gene was isolated from F3 populations by PCR reaction. After the sequencing of amplicons, the SNPs were identified between genotypes. According to the previous sequences, the proper site of the gene was determined and new primers were designed for PCR and HRM analysis. The results showed that among the genotypes tested for the resistance against the TYLCV virus, Comodoro, Speedy, and Matin genotypes were heterozygous and showed differentiation in the F3 generation, while Namib and SV8320 genotypes were resistant homozygous and their progeny did not show segregation. Regarding the ToMV virus, in the F3 generation of Matin, Comodoro, and Speedy 30, 12.5 and 12.5% of resistant plants were homozygous, respectively. Although a small number of resistant plants were observed among the F3 generation of SV8320 and Speedy, it can be concluded that these two genotypes were also heterozygous for this gene.

Finally, concerning Fusarium wilt disease, in the F5 generation, Matin, Comodoro, Speedy, SV8320, and Namib genotypes were all homozygous. In the field experiment of F₁, F_2, and F₃ generation of SV8320 high heritability was observed for yield per plant, days to flowering, and fruit shelf life. Overall, the findings of this study can inform tomato breeding programs aimed at producing resistant inbred lines.