Fine mapping of QTL for water use efficiency-related traits on chromosome 9 of Solanum habrochaites in the field

Fresh water is increasingly limited due to climate change. One way to reduce fresh water use by irrigated agriculture is to breed plants that can produce adequate yields with less water. A wild tomato, Solanum habrochaites, is more water stress tolerant than cultivated tomato, S. lycopersicum L. Our study aimed to fine map quantitative trait loci (QTL) for maturity, yield, and water use efficiency (WUE)-related traits (shoot dry weight and carbon isotope discrimination, increment C-13) on chromosome 9 in S. habrochaites using a set of 21 sub-near isogenic lines (sub-NILs). These sub-NILs and controls were evaluated in field experiments grown under full and reduced irrigation treatments across 2 yr. Genotype x environment interactions were significant, so the data was separated into subsets of environments for further analyses. Significant QTL were detected for 20 trait-environment combinations. All QTL were partially or completely coincident. The presence of the S. habrochaites allele at QTL was associated with later maturity, lower yields, and greater WUE. However, yield and increment C-13 exhibited no or low correlations with each other, suggesting these traits could be selected for improvement independently during breeding. Two of 21 sub-NILs showed superior performance for WUE and yield compared to controls. These two genotypes may prove useful in breeding programs to improve the WUE of tomato cultivars without negative effects on yield.

Automated summary

This study aimed to map quantitative trait loci (QTL) for maturity, yield, and water use efficiency (WUE) on chromosome 9 in a wild tomato, Solanum habrochaites. The presence of S. habrochaites allele at QTL was associated with later maturity, lower yields, and greater WUE. Two sub-near isogenic lines showed superior performance for WUE and yield compared to controls, and may be useful in breeding programs to improve WUE without negative effects on yield.