IDENTIFICATION OF PHYSIOLOGICAL RACES OF ASCOCHYTA RABIEI (PASS.) LAB. THE CAUSAL AGENT OF ASCOCHYTA BLIGHT ON CHICKPEA BY DIFFERENTIAL HOST

Chickpea, Cicer arietinum L. is one of the most important leguminous crops in Iraq .The crop is cultivated in northern area of Iraq, but still very restricted due to many agricultural problems and ascochyta blight , which is considered as a limiting factor to the cultivation of this crop . Ascochyta rabiei (Pass.)Lab. ,the causal agent of the disease is frequently undergoes genetic variation leading to the appearance of new strains which may cause resistance breakdown of the cultivated cultivars. This study was conducted to determine the genetic variations among fungus isolates by differential hosts.Results showed the existence of significant differences between the isolates, concerning disease severity. The disease severity was found to be 99.8% ,the highest, on the sensitive cultivar "Marakishy" and 47.63% , the lowest, on the resistante line ILC3279. Depending on these results , the isolates were considered as 4 physiological races. Race 1: is the weakest with disease severity above 66.6% on the cv. Marakishy and line ILC1929, Race 2: the mild one with disease severity above 66.6% on cv. Marakishy, ILC1929,cv. Rafidain, and line ILC482, Race 3: the agressive race with disease severity above 66.6% on most cultivars except line ILC3279, Race4: the highly aggressive race with a disease severity above 66.6% on all the test genotype. It was found that these races belong to 3 pathotypes: Pathotype I, the weakest one including race 1. Pathotype II, the mild one, including races 2 and 3, and pathotype III, the most severe one, including race 4