Genome Wide Association Study of Spot Blotch at Seedling and Adult Plant stages in Morocco and India

Abstract

Barley spot blotch caused by Cochliobolus sativus (Bipolaris sorokiniana) is one of the major constrains to barley production worldwide in warmer regions. This study was undertaken to identify and estimate effects of loci underlying quantitative resistance to spot blotch at seedling and adult plant stages. A panel of 261 barley genotypes (HI-AM) consisting of released cultivars from North and South America, Europe, Australia, advanced breeding lines, and landraces from ICARDA, was screened for resistance to spot blotch. Seedling resistance screening was conducted using two most virulent isolates from Morocco (ICSB and SB54), while adult plant resistance was assessed at two hot spot locations (Faizabad and Varanasi) in India under artificial inoculation using a mixture of prevalent isolates. Both GLM and MLM model were employed in Tassel using principal component analysis and Kinship Matrix as covariates. Genome wide association mapping indicated a total of 23 QTL at seedling stage (14 for isolate ICSB and 9 for isolate SB54), while 15 QTL were detected for adult plant resistance (6 at Faizabad and 9 at Varanasi). Common QTL at seedling and adult plant stages were found across all barley chromosomes. QTL detected explained together the 73.24% of the variance for seedling resistance to isolate ICSB and 49.26% for isolate SB54. QTL for adult plant resistance explained together 38.32% and 44.09% at Faizabad and Varanasi, respectively. Several QTL identified in this study were also reported before in bi-parental and association mapping populations studies supporting our results. The promising QTL detected at both stages, once validated, can be used for MAS in spot blotch resistance breeding program globally.