PATHOGENIC SPECIALIZATION OF PUCCINIA-HORDEI OTTH IN AUSTRALIA, 1966-1990

One hundred and fifty-four isolates of the leaf rust pathogen (Puccini a hordei), collected from infected barley plants in Australia between 1966 and 1990, were typed to determine virulence with respect to the r esistance genes Rph1 to Rph9, Rph12 (Triumph) and several uncharacteri zed resistance sources. The Australian cultivar, Prior, reacted differ entially to the isolates examined, and is believed to possess a gene w hich is also present in addition to Rph2 in Reka 1. Virulence and avir ulence on Prior were designated P+ and P- respectively. Eleven distinc t pathotypes (pt) were identified, with pt 243 P+ and 243 P- predomina ting in samples collected between 1966 and 1979. In the 1980s, pt 210 P+ was most commonly isolated from samples collected in Queensland and northern New South Wales, and although a range of different pathotype s was present in southern Australia, pt 200 P+ was most frequent in th is region. Virulences to genes Rph1, Rph2, Rph4, Rph5, Rph6, Rph8, Rph 9 and Rph12 have been detected, and only Rph3 and Rph7 are likely to b e of value in protecting future Australian barleys from the disease.