Pathogenic variability of a Uruguayan population of Bipolaris sorokiniana in barley suggests a mix of quantitative and qualitative interactions

Abstract

Race-specific and race-non-specific interactions with barley have been previously reported for Bipolaris sorokiniana. The aims of the study were to characterize a Uruguayan population of B. sorokiniana, to determine the nature of the interactions, and to identify a set of the most informative barley genotypes to characterize the pathogen. Infection responses of 322 single-spore isolates of B. sorokiniana collected from 2001 to 2010 were assessed for their interaction with 35 barley genotypes after inoculation at the two-leaf stage under controlled conditions on a 1–9 scale. After removal of the most redundant isolates, the interactions of 147 isolates were analyzed with Hierarchical Clustering on Principal Components, resulting in eight clusters of barley genotypes and seven clusters of B. sorokiniana isolates. A set of 12 potential differential barley genotypes grouped into 11 clusters that interacted in a partially specific but also in a quantitatively variable manner with the 147 isolates. Despite some clear isolate-specific interactions, the predominately quantitative interactions found make it unlikely that a universal differential set could be used to monitor diversity worldwide.