Pathogenic race and mating type of Pyricularia oryzae from Soviet Union, China, Nepal, Thailand, Indonesia and Colombia.

Abstract

A total of 130 isolates of Pyricularia oryzae from 6 countries were tested for the identification of pathogenic race and mating type. The number of races identified from country of origin was, Soviet Union-3 Japanese races [3 international races], China-7 [9], Nepal-2 [2], Thailand-3 [2], Indonesia-4 [4], and Colombia-5 [12]. The reaction of these races identified by means of Japanese and international rice cultivars did not always correspond. About 40% of the isolates used were of untetermined pathogenic race, because of inconsistent host reaction. The phenotypic variability in pathogenic reaction could be due to the heterogeneity of the differential rice cultivars as well as to the pathogenic change of the blast fungus itself. The presence of both mating types was confirmed in the isolates from China and Colombia, but in the Russian and Nepalese collection mating type A was only detected. On the other hand, all of the Indonesian isolates used were of mating type a.