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. tri tici 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 provid e comparisons of grain yield and quality. Barleys with Rpgl, which con fers resistance to races of P. graminis f. sp. tritici other than Pgt- QCCJ, were generally more resistant than cultivars or lines that lacke d this gene. However the severity of losses indicated that under high disease pressure the resistance conferred by Rpgl would not be effecti ve. Yield reductions of up to 29% were recorded and were generally ass ociated with reduced grain size and weight. The continued presence of Pgt-QCCJ as a component of the P. graminis population in the United St ates, since it was first detected in 1989, indicates that Pgt-QCCJ rem ains a threat to commercial barley production.