Positional Cloning of a QTL, qDHY.3BL, on Chromosome 3BL for Drought and Heat Tolerance in Bread Wheat

Drought and heat are major abiotic stresses dramatically impacting wheat production by reducing final grain yield. Yield under drought is a complex trait highly dependent on genotype x environment interactions and controlled by multiple genes. Identifying the genetic determinants of grain yield in stress-prone environments is essential for the breeding of cultivars able to sustain wheat production.

A quantitative trait loci (QTL) on the bread wheat chromosome 3BL, qDHY.3BL, was identified in the doubled-haploid population of a cross between the drought tolerant line RAC875 and the susceptible line Kukri. The RAC875 allele was positively associated with yield, thousand grain weight and early vigour under drought and heat stress.

The development of SNP-based markers using the IWGSC 3B pseudomolecule and the Whole Genome Assembly v0.4 of Chinese Spring, combined with whole-genome shotgun sequencing data of the parental lines enabled the fine mapping of qDHY.3BL in RAC875. The identification of seven new recombination points in the narrowed QTL interval, combined with the anchoring of the QTL onto new wheat assemblies enabled us to refine the QTL to a list of 22 genes in a ~ 1 Mbp interval. We identified haplotypes at the QTL interval in a wheat diversity panel of more than 800 accessions. We will describe gene expression analysis of the candidate genes and a physiological study of near-isogenic lines to identify the gene(s) responsible for qDHY.3BL.