Components of resistance in barley to stem rust: receptivity, urediniospore production, latent period, and infection response in adult plants

Abstract

Resistance in barley (Hordeum vulgare) to stem rust, caused by Puccinia graminis f.sp. tritici, is often variably expressed. This study was undertaken to evaluate several components of stem rust resistance in the barley cultivars or lines Tupper, Robust, Q21861, SB90585, SB91702, and Harrington and to compare them with the susceptible wheat cultivar Little Club (Triticum aestivum). Stems of adult plants were quantitatively inoculated with urediniospores of races QCC, QFC, and TPM of P. graminis tritici. Significant differences in receptivity, urediniospore production, and latent period were observed among the barley lines and between all barley lines and Little Club wheat. The degrees of receptivity and the levels of urediniospore production on the barley lines were related to the presence or absence of the specific resistance genes Rpg1, rpg4, and possibly additional noncharacterized gene(s). Receptivity was the most strongly expressed of all of the components measured. Receptivity, spore production, and infection response were highly correlated to each other, but only infection response was significantly correlated to latent period. The usefulness of measuring these components to evaluate resistance in barley breeding is discussed. Keywords: barley, Hordeum vulgare, stem rust, Puccinia graminis tritici, resistance, components.