LAUSR

Tan spot, caused by Pyrenophora tritici-repentis, is one of the major wheat diseases in southern Brazil as well as in the wheat production areas of several other countries. The fungal isolates have been classified into eight races according to the production of three fungal necrotrophic effectors. The knowledge about the pathogen population structure is essential for disease control strategies, but such information is lacking in Brazil. The aim of this study was to determine the P. tritici-repentis race structure of Brazilian isolates using, for the first time, biological and molecular techniques. P. tritici-repentis isolates were characterized for their virulence on a set of wheat genotypes, and for the presence of ToxA and ToxB gene. The results from the PCR amplification with the gene specific primers showed that all Brazilian P. tritici-repentis isolates carried ToxA, but no ToxB is present. Race typing on the set of wheat genotypes indicate 65% of the isolates were race 2 while 35% were race 1. This is the first study on the P. tritici-repentis race structure in Brazil and the information will be useful to the local wheat breeders who aim to improve tan spot resistance in wheat cultivars.