Pathogenic specialization of Puccinia hordei Otth. in Australia, 1966-1990

One hundred and fifty-four isolates of the leaf rust pathogen (Puccinia hordei), collected from infected barley plants in Australia between 1966 and 1990, were typed to determine virulence with respect to the resistance genes Rphl to Rph9, Rphl2 (Triumph) and several uncharacterized resistance sources. The Australian cultivar, Prior, reacted differentially to the isolates examined, and is believed to possess a gene which is also present in addition to Rph2 in Reka 1. Virulence and avirulence on Prior were designated P+ and P- respectively. Eleven distinct pathotypes (pt) were identified, with pt 243 P+ and 243 P- predominating 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 pathotypes was present in southern Australia, pt 200 P+ was most frequent in this region. Virulences to genes Rphl, Rph2, Rph4, Rph5, Rph6, Rph8, Rph9 and Rphl2 have been detected, and only Rph3 and Rph7 are likely to be of value in protecting future Australian barleys from the disease.