Complex Relationships among Water Use Efficiency‐Related Traits, Yield, and Maturity in Tomato Lines Subjected to Deficit Irrigation in the Field

Abstract

Cultivated tomato (Solanum lycopersicum L.) is susceptible to abiotic stresses, including water stress. In contrast, a wild tomato relative, S. habrochaites S. Knapp & D.M. Spooner, is highly tolerant to abiotic stresses. Previously, we used a set of 18 sub‐near‐isogenic tomato lines (sub‐NILs) containing chromosome 9 introgressions from S. habrochaites to investigate the genetic basis of tolerance to rapid‐onset water stress imposed by root chilling. In the present study, this same set of 18 sub‐NILs was subjected to slow‐onset water stress imposed by deficit irrigation in field experiments conducted for 2 yr. Trait data were analyzed with principal component analysis, ANOVA, and MANOVA to investigate the underlying relationships among proxy traits for water‐use efficiency (WUE) including carbon isotope discrimination (Δ13C) and specific leaf area (SLA) with horticultural traits including maturity and yield. The majority of total phenotypic variation among the sub‐NILs was accounted for by Δ13C and SLA, with minor contribution from the horticultural traits. While many trait QTL were coincident or overlapping, our analyses suggest that the genes controlling QTL for Δ13C and SLA in this chromosome 9 region are distinct from each other and also from genes controlling maturity and yield. This introgressed region contains potentially valuable wild alleles for breeding cultivated tomatoes with improved WUE while selecting for yield maintenance.