Quantitative Trait Loci for Water‐Stress Tolerance Traits Localize on Chromosome 9 of Wild Tomato

Abstract

A wild tomato species (Solanum habrochaites S. Knapp & D.M. Spooner) is tolerant to many abiotic stresses, including limited water, and can serve as a valuable genetic resource for breeding cultivated tomato (S. lycopersicum L.). Previously, we developed and used a set of 18 sub‐near‐isogenic lines (sub‐NILs) containing introgressions from chromosome 9 of S. habrochaites to determine the genetic basis of tolerance to rapid‐onset water stress imposed by root chilling. In this study, we used this same set of 18 sub‐NILs to investigate the genetic basis of tolerance to slow‐onset water stress in the field imposed by restricted irrigation (with full water treatment as control) in replicated experiments for 2 yr in Davis, CA. The sub‐NILs were evaluated for C isotope discrimination (Δ13C), specific leaf area (SLA), shoot dry weight (SDW), yield, and other horticultural traits. A total of 19 QTL for Δ13C, SLA, SDW, yield, and maturity traits were mapped on chromosome 9. Significant genotype × environment interactions were detected for Δ13C, SLA, yield, and maturity. Agriculturally beneficial effects were conferred by S. habrochaites alleles at QTL for traits associated with water‐stress tolerance: low Δ13C, low SLA, and high SDW. The majority of QTL mapped to the centromeric end of the introgression, suggesting a gene‐rich region containing valuable wild alleles for breeding tomato for improved abiotic stress tolerance.