Distribution of races and Tox genes in Pyrenophora tritici-repentis isolates from wheat in Argentina

MORENO, MV; STENGLEIN, S.; PERELLÓ ANALÍA

TROPICAL PLANT PATHOLOGY

SOC BRASILEIRA FITOPATHOLOGIA

Año: 2014

1982-5676

Tan spot, caused by Pyrenophora tritici-repentis, is a common disease of wheat in all the agroecological wheat area of Argentina. In this study the pathogenicity and Tox genes presence of 65 isolates collected from different Argentinean regions were analyzed. Pathogenic assays were made on wheat cultivars and lines recommended for race determination, Glenlea, Salamouni, Katepwa, M-3, 6B365 and 6B662. Thirty-six isolates could be assigned to races; based on reaction type: one isolate classified as race 1, four isolates as race 2, one as race 3, 15 as race 4, one as race 5, one as race 6 and 13 isolates were classified as race 8. The remaining isolates could not be classified into races. The presence/absence of the ToxA, ToxB, ToxB-like and toxb genes using PCR specific-primers revealed that 57 isolates have the fragment corresponding to the ToxA gene whereas one isolate have the fragment corresponding to the ToxA and ToxB genes. No correlation between phenotypic races and presence/absence of the toxin amplification products was shown. Most of the isolates produced chlorosis on different cultivars but only one of them amplified for the ToxB gene. These results indicated that different races of P. tritici-repentis are present in Argentina, and that the isolates of P. tritici-repentis that induce necrosis and chlorosis might produce a novel toxin(s) on wheat.