شناسايي جمعيت هاي ايراني gaeumannomyces graminis var. tritici با استفاده از مطالعات ريخت شناسي ، مولكولي و بيماري زايي

IDENTIFICATION OF IRANIAN POPULATIONS OF Gaeumannomyces graminis var. Tritici USING MORPHOLOGICAL, MOLECULAR AND PATHOLOGICAL STUDIES

Gaeumannomyces graminis (Sacc.) Arx & Olivier, is one of the most important soilborne plant pathogens, and the causal agent of take-all disease of cereals and grasses world wide. In a survey conducted during 2005-06 wheat growing seasons, 52 isolates were obtained from diseased samples collected from different provinces of Iran including Fars, Golestan, Markazi, Mazandaran and Tehran. Pathogenicity tests indicated that all isolates were pathogenic on wheat but only ten isolates (out of 52) were pathogenic on oat. Disease severity among isolates and pathogenicity on two hosts (wheat and oat) were significantly different. Disease severity of 64% of the isolates was over 60% on the wheat seedling. Except for one isolate from Naghsh-e-Rostam, Fars province, all produced simple hyphopodia. Average length of ascospores produced on wheat and oat were measured 67-85 /mi and 66-88 fim, respectively. These isolates were identified as G. graminis var. tritici Growth rates of isolates at 25°C on PDA ranged between 1.81-5.35 mm/day. There was no correlation between mycelial growth rate and virulence isolates on wheat. In this study for molecular identification of isolates of G. graminis var. tritici specific primers were used. These primers revealed that with the exception of three isolates which belonged to the type B, all the remaining 49 isolates were of the type A. The Ggt A and B-type isolates produced PCR products consistent with the predicted size of 93 and 132 bp, respectively. These primers did not amplify any product in G. graminis var. graminis and Magnaporthe grisea as control.