Pathogenicity variation of Didymella rabiei causal agent of chickpea blight from Ilam and Kermanshah provinces

Ascochyta blight caused by Didymella rabiei is one of the most important diseases of chickpea in Ilam and Kermanshah Provinces, Iran. In order to determine the pathogenicity variation of Didymella rabiei populations, infected plants in field crops of different regions of both provinces were sampled. One hundred isolates were isolated by chickpea seed meal dextrose agar media. These isolates were categorized in 10 groups based on collection regions. These isolates showed little differences cultural morphological characteristic, for this regard, we chose one isolate as a representative for each group. Pathogenicity of representative isolates from each of the 10 groups were tested on 12 differential chickpea lines as randomized completely block design in the greenhouse condition. Two-week-old plants were sprayed until run-off with a conidial suspension adjusted to 2 x 105 pycnidiospores mL-1. Disease is scored on spore inoculated plants three weeks after treatment. Based on disease reaction on 10 differential chickpea lines 8 virulence forms were identified. The result of this research showed that, there are different virulence forms in two provinces and also population of this fungi composed of several virulence forms. Therefore the efforts should be focused on introduction of multigenic and durable chickpea resistant lines against Ascochyta blight.