Identification of gene loci associated with seedling resistance to common spot blotch disease of barley using association analysis method

Spot blotch caused by the fungal pathogen Cochliobolus sativus and is an important leaf disease of barley. To identify gene loci associated with seedling resistance to spot blotch in a population consisting of 142 modern European two-row spring barley cultivars, the genotypic data from 407 AFLP and SSR markers and phenotypic data derived from responses of barley cultivars to four isolates of spot blotch (Csh-1 and Csh-16 isolates from barley and Cst-42 and Cst-151 isolates from wheat) were used. These isolates were collected from Mazandaran, Golestan and Khorasan-e-Razavi provinces. The results showed that most of the studied cultivars at seedling stage were resistant to Csh-16 and Cst-42 isolates, but the highest number of susceptibility reactions to Csh-1 and Cst-151 isolates were observed. Population structure analysis subdivided the studied cultivars into two subpopulations (K=2). Association analysis using general linear model (GLM), six and twelve markers and using mixed linear model (MLM), three and four markers associated with resistance to isolates separated from barley and wheat leaves was identified, respectively, that were significantly to (P≤0.01). These QTLs were mapped on chromosomes 2H, 3H, 5H, 6H and 7H. All of the reported QTLs were specific for each isolate and only Bmag0225-161 marker was common between two isolates Csh-1 and Cst-151. The Identified markers can be used in breeding programs to develop disease resistant cultivars after validation.