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.

Genetic diversity in cultivated yam bean (Pachyrhizus spp.) evaluated through multivariate analysis of morphological and agronomic traits

“…In the full MANOVA, the primary root accounted for about 43.41%of the variance (source G). Across locations, the primary root accounted for 43.50% (source G) (at location Songhai) and 43.47% (at location Niaouli) of variance associated with G. Applying MANOVA to tomato trial, Lounsbery et al (2016) reported minor rank changes among genotypes across different locations. These findings are consistent with the results presented here in yam bean.…”

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

“…The linkage map of the S. habrochaites introgressed chromosome 9 region is displayed as a vertical line, with the location in cM denoted to the left and marker names to the right. To the right of the linkage map are primary trait QTL (see Lounsbery et al, 2016) included here for convenience. To the left are QTL for PC1 to PC4 as identified in the present work.…”

“…The relationships among quantitatively inherited traits and the genes controlling them are often complex, and so coincident QTL detected at lower mapping resolution are not necessarily coincident upon higher‐resolution mapping (Mackay et al, 2009; Alonso‐Blanco and Méndez‐Vigo, 2014). Field trait QTL identified as coincident in our field study (Lounsbery et al, 2016) suggest that the genes controlling these primary traits are located within a relatively defined region of chromosome 9, but this does not necessitate an underlying relationship for the regulation of these genes. The goal of our present study was to obtain a more in‐depth understanding of the genetic interactions among these traits.…”

“…Raw data for sub‐NILs (C1–C18) on a per‐plot basis for each of the seven primary traits (Δ 13 C, SLA, DAPG, DAPR, SDW, RYLD, and TYLD) and PC1 to PC4 across all locations were used to obtain Pearson's correlation coefficients ( r ) using PROC CORR in SAS. Lounsbery et al (2016) identified significant Genotype × Location effects in ANOVAs of all primary traits except for SDW and TYLD. To account for these significant Genotype × Location interactions in the Pearson's correlations, partial correlations by location were produced.…”

“…We evaluated primary traits that are, or may be, associated with plant response to water stress, including Δ 13 C, SLA, and several maturity and yield‐related traits. We mapped 19 QTL for eight traits on chromosome 9, and the majority of field trait QTL localized to the proximal (centromeric) end of the introgressed region (Lounsbery et al, 2016). Most field trait QTL appeared coincident, yet none co‐localized with QTL stm9 .…”