Association Mapping of Russian Wheat Aphid Resistance in Barley as a Method to Identify Diversity in the National Small Grains Collection

Abstract

ABSTRACTRussian wheat aphid (RWA) (Diuraphis noxia Kurdjumov) infestations of barley (Hordeum vulgare L.) cause chlorotic leaf spotting and streaking and prevent unrolling of leaves, which traps spikes and reduces grain yield. Resistant accessions identified in the USDA‐ARS National Small Grains Collection (NSGC) were used to develop adapted, resistant germplasm and cultivars. This study identified loci affecting RWA resistance and diversity in the NSGC using association mapping. Resistant and susceptible accessions, breeding lines, and cultivars were genotyped with Diversity Arrays Technology (DArT) markers and phenotyped for RWA responses. A core set of nine markers explained 83% of the variation for chlorosis. Most resistant and susceptible accessions had opposite genotypes at each of these markers. The six susceptible adapted cultivars were exceptions and shared the haplotype of the resistant accessions. Variability at four additional loci associated with resistance did not sufficiently explain phenotypic variability between resistant accessions and susceptible cultivars. Examining subsets of the data identified six additional markers associated with RWA response, which discriminated between resistant accessions and susceptible cultivars. Additional investigation is necessary to better understand the genetics of RWA resistance. However, this study provided useful information on diversity in the NSGC and suggested that RWA resistance is a complex trait that may share physiological components with other characteristics that were selected during domestication.