IDENTIFICATION OF CANDIDATE GENES UNDERLYING A NOVEL QTL FOR ROOT LENGTH AND DIAMETER IN BARLEY IN RESPONSE TO SALINITY

Abstract

Salinity is a major agricultural problem that decreases growth and yield of crops and is expected to worsen with climate change. Improving salt tolerance through breeding could be facilitated by identification of genetic loci and candidate genes affecting root traits that enhance water and nutrient uptake while limiting accumulation of toxic ions. In this study, a Clipper x Sahara 3771 doubled haploid (DH) barley mapping population was screened for root growth responses to saline conditions in a controlled environment. Quantitative trait loci (QTLs) were mapped for root traits including seminal root length, root diameter and root potassium. Major QTLs affecting seminal root length and average root diameter were detected in the distal region of the short arm of chromosome 2H, indicating that this region is a key determinant of root architecture under both control and saline conditions. The linkage map was improved by using newly designed assays for SNPs on chromosome 2H and a 2.5-Mb interval was identified for investigation of candidate genes. Bulked segregant RNA sequencing (BSR-Seq) of contrasting salt-tolerant and salt-sensitive DH lines identified differentially expressed genes associated with root growth maintenance and ion homeostasis in root tips. These findings identify specific region on chromosome 2H as a major genomic region affecting barley root architecture, especially under saline conditions, and identify differentially expressed candidate genes in that region.