Phenotypic characterization of the Hordeum bulbosum derived leaf rust resistance genes Rph22 and Rph26 in barley

Abstract

Aims: Two introgression lines (ILs), 182Q20 and 200A12, which had chromosomal segments introgressed from Hordeum bulbosum in H. vulgare backgrounds, were identified to show seedling resistance against Puccinia hordei, possibly attributed to two resistance genes, Rph22 and Rph26, respectively. This study characterized the phenotypic responses of the two genes against P. hordei over different plant development stages. Methods and Results: Using visual and fungal biomass assessments, responses of ILs 182Q20, 200A12 and four other barley cultivars against P. hordei were determined at seedling, tillering, stem elongation and booting stages. Plants carrying either Rph22 or Rph26 were found to confer gradually increasing resistance over the course of different development stages, with partial resistant phenotypes (i.e. prolonged rust latency periods, reduced uredinia numbers but with susceptible infection types) observed at seedling stage and adult plant resistance (APR) at booting stage. A definitive switch between the two types of resistance occurred at tillering stage. Conclusions: Rph22 and Rph26 derived from H. bulbosum were well characterized and had typical APR phenotypes against P. hordei. Significance and Impact of the Study: This study provides important insights on the effectiveness and expression of Rph22 and Rph26 against P. hordei during plant development and underpins future barley breeding programmes using non-host as a genetic resource for leaf rust management.