Race structure of Pyrenophora tritici-repentis prevalent on wheat in Argentina.

MORENO M. V.; STENGLEIN S.A.; PERELLÓ, A. E.

Simposio; International Symposium Plant protection and Plant Health in Europe; 2011

Tan spot caused by Pyrenophora tritici-repentis (Ptr) is a common disease of wheat worldwide that increased in the South Cone region in the last few years. The race structure and Tox genes of 65 monosporic isolates of Ptr collected at different regions of Argentina were analyzed. Virulence tests were conducted on the set of cultivars and lines Glenlea, Salomouni, Katepwa, M-3, 6B365 and 6B662. Based on the reaction types,  33 Ptr isolates were grouped into seven races, The rest of the isolates could not be classified into races. The two most common races were 4 (11 isolates, 16,9%) and 8 (13 isolates, 20%). The presence/absence of the Tox A, Tox B and tox b genes using PCR specific-primers revealed that 57 isolates amplified the fragment that correspond to the Tox A gene, one isolate to the Tox A and Tox B, and the remaining seven isolates lacked these genes. Low association was found between phenotypic races and toxin production genes. Although some isolates amplified for the Tox A gene, they did not express it through the production of necrosis. Most of the isolates produced chlorosis on different cultivars but only one of them amplified for the Tox B gene. These results indicates a diverse races population of Ptr on wheat in Argentina,  and suggest novel toxin(s) involved from isolates  inducing necrotic-chlorotic tan spot symptoms.