Association analysis for adult plant resistance to leaf stripe disease (Pyrenophora graminea) in spring barley cultivars

Abstract The leaf stripe disease of barely caused by the seed transmitted hemi-biotrophic fungal pathogen, Pyrenophora graminea is an important disease of barley worldwide. The present study was carried out to determine the genetics of leaf stripe resistance in an association mapping population consisted of 141 European two-rowed spring barley cultivars and to identify new sources of resistance. The field trials were set up in a randomized complete block design with three replications during three consecutive growing years (2016-19). In the first year, the genotypes were sown in plots, adjacent to the highly susceptible spreader rows to be inoculated via natural infection at the flowering stage. In addition to the leaf stripe incidence, associations of some agronomical relevant traits including days to heading, days to maturity, plant height, number of seeds per spike and thousand kernel weight with AFLP and SSR markers were determined. The results of analysis of variance in two years showed significant variation between genotypes for all the traits. Four QTLs for leaf stripe resistance at the adult plant stage, designated as Rpgq1 to Rpgq4 , were mapped on chromosomes 5H (two QTL), 6H and 7H, from which Rpgq2 QTL on chromosome 5H, showed coincidence with the map position of two QTLs for days to healing and days to maturity. We found a significant difference between the level of leaf stripe incidence in 100 cultivars carrying the Mlo wild-type and of 41 carrying mlo mutant alleles, indicating that that the mutant alleles of the MLO gene which are effective against the biotrophic barley powdery mildew pathogen ( Blumeria graminis fsp. hordei ) confers increased susceptibility to the leaf stripe pathogen.