بررسی پراکنش، فراوانی و اهمیت نسبی قارچ های بیماریزای طوقه و ریشه ماش در استان خوزستان

Mungbean (Vigna radiate (Wilczek)) because of having high protein content, short geowing period and good tolerance to high temperature is one of the most important pulse crops in tropical and sub tropical regions. Mungbean is widely planted in Khuzetan province and the area under its cultivation in Khuzestan is significantly more than any other provinces in Iran. Fungal diseases of root and crown of this plant are among its important diseases worldwide. In this investigation, distribution and identification of the causal agents were studied. During summer and fall of 2010 and 2011, 78 samples were collected from Mollasani, Dezful, Shushtar, Abbid, Gotvand, Ramhormoz and Susangerd which are the main Mungbean cultivation areas in Khuzestan. Macrophomina phaseolina, Rhizoctonia solani and Fusariun solani were recovered from these samples. The collected data illustrated that M. phaseolina with the occurrence frequency of 70.51% was the main cause of the disease. R. solani with 17.95 and F. solani with 11.54% occurrence frequency belonged to a statistically separate group. Moreover, the reaction of the M. phaseolina isolates to potassium chlorate was studied. According to the results, the Macrophomina isolates were divided in two groups, chlorate sensitive to 77.3% and chlorate resistant to 22.7%. Among the chlorate sensitive isolates, two phenotypes - feathery and restricted growth- were identified while the phenotype of chlorate resistant isolates was dense growth. Statistically investigation into pathogenicity of different phenotypes of Macrophomina isolates showed that chlorate resistant isolates with dense growth intensively made infection and sensitive isolates with feathery phenotype ranked second, and sensitive isolates with restricted phenotype had the least pathogencity.