Genetic basis of the lobedness degree in tomato fruit morphology

Fruit shape is a key trait in tomato (Solanum lycopersicum L.). Since most studies focused on proximo-distal fruit morphology, we hypothesized that unknown QTLs for medio-lateral direction ones could be found analysing segregating populations where major shape genes are fixed. We examined the diversity of fruit morphology in medio-lateral direction; defined divergent traits in cultivars carrying identical genetic constitution at LC and FAS genes; and identified QTLs for lobedness degree (LD) by a QTL-seq approach. We found that LC and FAS genes were not enough to explain LD variability in a large tomato collection. Then, we derived F-2 populations crossing cultivars divergent for LD where LC and FAS were fixed (Yellow Stuffer x Heinz 1439 [F(2)YSxH] and Voyage x Old Brooks [F(2)VxOB]). By QTL-seq we identified a QTL for LD on chromosome 8 in both F-2, which was validated in F(2)YSxH by interval mapping accounting for similar to 17% of the variability. Other two QTLs located on chromosomes 6 and 11 with epistasis explained similar to 61% of the variability in the F(2)VxOB. In conclusion, three novel QTLs with major effect for LD (ld6, ld8, and ld11) were identified through the study of diversity and genetic segregation in intraspecific tomato crosses.

Automated summary

In this study, three novel QTLs determining lobedness degree (LD) in tomatoes were identified through the study of diversity and genetic segregation.