Haplotype diversity at nine spot blotch resistance QTL in barley

Spot blotch (SB), caused by <i>Bipolaris sorokiniana</i> is becoming an important barley disease in humid, temperate growing regions, including Uruguay. The narrow genetic base of current donors of resistance and recent changes in pathogen virulence have driven the search for novel sources of resistance. In this study, a diverse collection of 39 barley genotypes was evaluated for SB resistance, and genetic relationships, population structure, and haplotype diversity were investigated using 27 simple sequence repeats (SSRs) and eight sequence-tagged sites (STS) markers linked to nine QTL for SB resistance located on chromosomes 1H, 2H, 3H, 4H, and 7H. Fourteen barley genotypes expressed high and moderate SB resistance at seedling and adult plant stages. Distance and model-based cluster analyses revealed that the 14 selected lines clustered in four groups consistent with geographical origin and pedigree relatedness. Reference SB resistant haplotypes were poorly represented. Based on these results, we suggest that these 14 lines are likely candidates to carry novel genes or alleles for SB resistance. Further research may expand the understanding of the genetic architecture of this trait.