A novel QTL qRYM-7H for barley yellow mosaic resistance identified by GWAS and linkage analysis.

Barley (Hordeum vulgare L.) is the fourth largest cereal crop in the world after rice, wheat and maize. Barley yellow mosaic disease (BYMD) is a serious threat to winter barley production. The evolution and mutation of virus strains lead to the breakdown of the resistance of the originally resistant varieties. It is therefore vital to explore new BYMD resistance genes. In this study, a natural population (334 barley varieties or lines) and a double haploid population derived from the cross between Tam407227 and Franklin were used to search for new quantitative trait loci (QTL) for BYMD resistance. Two major QTL on chromosomes 3H and 7H, respectively, were detected from the genome wide association study and validated in the DH population. Among them, The QTL on 3H (qRYM-3H/qTFRYM-3H) was confirmed to be the reported BYMD resistance gene eIF4E by haplotype analysis. And the QTL on 7H (qRYM-7H/qTFRYM-7H) is a novel QTL that has not been reported before. Another QTL on 2H was identified from the DH population. This QTL is more likely the Rmy16^Hb reported previously. These three QTL showed an additive effect on improving BYMD resistance with the average disease scores from 2.45 (all sensitive alleles for these three QTL) to 0.62 (all tolerant alleles for these three QTL). The candidate genes for the novel QTL qRYM-7H/qTFRYM-7H were predicted based on transcriptome sequencing and qPCR analysis.