Detection of QTL and QTL × environment interaction for scald resistance in a two-row × six-row cross of barley

Abstract

Leaf scald caused by Rhynchosporium secalis, is a serious disease of barley (Hordeum vulgare L.) in Tunisia. A doubled-haploid barley population, from a cross between the two-rowed ‘Roho’ and the six-rowed ‘L90’ cultivars, was evaluated for its reaction to scald under natural infection in replicated field trials for two years. Phenotypic variation among doubled-haploid lines was significant for disease reaction in both environments (cropping seasons) and genotype × environment interaction was also significant. Heritability estimates were high in both seasons and significant correlation was noted between scald reactions recorded in the two seasons. Segregation of 34 single sequence repeat markers was used for quantitative trait loci mapping. Single-marker analysis was applied for individual and for combined environments to determine the effect of each molecular marker on scald resistance. In total, six QTLs with additive effects were mapped on chromosomes 2H, 3H, 4H, 6H and 7H which explained from 4.4 to 11.7% of the phenotypic variance. Among these, only QTLs linked to WMS6 (4H) and to HVM31 (6H) showed significant QTL × environment interactions. QTLs associated to HVM36 (2H) and to Bmag0571 (7H) were the most significant for scald resistance and the most insensitive to the environment. Another stable QTL was identified, for the first time, in the vicinity of the Vrs1 locus on the 2H chromosome. For this QTL, the two-rowed parental allele reduced disease severity. These chromosomal regions that affect scald resistance independently of the environment would be of great interest in marker-assisted selection.