The Effect of Race QCCJ of Puccinia graminis f. sp. tritici on Yield and Quality in Barley.

The progress of epidemics of race QCCJ of Puccinia graminis f. sp. tritici was examined in field plots of the barley cultivars Robust, Excel, Stander, Azure, Stark, Larker, Bonanza, and Steptoe. In addition, a potential source of resistance (cv. Diamond), and a susceptible line (ND11075) were included. Rust-free treatments were maintained to provide comparisons of grain yield and quality. Barleys with Rpg1, which confers resistance to races of P. graminis f. sp. tritici other than Pgt-QCCJ, were generally more resistant than cultivars or lines that lacked this gene. However the severity of losses indicated that under high disease pressure the resistance conferred by Rpg1 would not be effective. Yield reductions of up to 29% were recorded and were generally associated with reduced grain size and weight. The continued presence of Pgt-QCCJ as a component of the P. graminis population in the United States, since it was first detected in 1989, indicates that Pgt-QCCJ remains a threat to commercial barley production.