تشكيل فرم جنسي ، پراكندگي تپ هاي سازگاري جنسي و تنوع ژنتيكي در جدايه هاي Didymella rabiea عامل برق زدگي نخود در استان فارس

DISTRIBUTION OF MATING TYPE, TELEOMORPH FORMATION, AND GENETIC DIVERSITY IN DIDYMELLA RABIEI THE CAUSAL AGENT OF CHICKPEA BLIGHT IN FARS PROVINCE

During chickpea growing season of 1998-1999 , on a time regulated schedule, several surveys were carried out in warm and cold chickpea growing areas in Pars province. Forty isolates of Ascochyta rabiei (Teleinorph : Didymella rabiei ) were collected from symptomatic chickpea tissues in different parts of the province and used for cultural and morphological characters. Analysis of variance of morphological characters in asexual stage, (growth rate of colony, sprorulation, pycnidium and pucnidiospore size), and sexual stage (pseudothecium, asci and ascospore size) showed that there were significant variations among isolates. On the basis of the above features, they could be differentiated into several groups. The interaction of forty isolates of the pathogen with standard tester isolates ( MAT-1 & MAT-2) .showed that 38 isolates (%95) belonged to MAT-1 and two isolates (%5) to MAT-2. Microscopic studies of naturally infected tissues and tissues inoculated with standard isolates (MAT-1 &MAT-2), which had been kept for two years under natural conditions, showed that the sexual stage (pedudothecium) of the fungus was developed. This is the first report of the occurrence of sexual stage under natural conditions in Fars province. On the basis of host pathogen interactions on ten differential chickpea cultivars under greenhouse conditions and data analysis, four pathogenicity groups (A-D) were identified among isolates of Ascochyta rabiei. According to the present results, the use of race for the isolates of the causal agent was not suggested.