عنوان مقاله [English]
Many fungi cause sugar beet root rot during various stages of the plant growth. Among them Rhizoctonia spp. induce crown rot, dry rot and violet root rot on sugar beet (Whitney and Duffos,1986). Root rot caused by Phytophthora drechsleri has been observed in fields with excessive moisture (Habibi,1975). Pythium aphanidermatum has been recognized as one of the causal agents of sugar beet, damping-off, root rot and seed deterioration (Ahmadinejad and Okhovat, 1976). Rhizopus arrhizus has been also reported as one of the fungi involved in crown rot of sugar beet (Habibi,1977). In order to determine pathogenic fungi involved in sugar beet root rot and their distribution in Kermanshah province, this investigation was carried out during 1998-1999. Forty-one fields in different parts of the province were surveyed. At every field some information about previous crop in rotation, method of irrigation, source of irrigation water and disease severity was recorded. From each field, 2-5 root samples showing root rot symptoms were collected and transferred to laboratory. A soil sample was also collected and analyzed in the laboratory. Ninty eight isolates belong to Fusarium spp., Rhizoctonia solani ,Binucleate Rhizoctonia , Phytophthora drechsleri ,Pythium aphanidermatum,Rhizopus arrhizus,Rhizopus stolonifer,Macrophomina phaseolina, Phoma betae , Mucor spp. and Geotrichum sp. were isolated. In this study, although the majority of the isolates belonged to Fusarium spp., they could not induce root rot symptoms in pathogenicity tests. The most severe symptoms of root rotwere induced by R. solani ,P. drechsleri , P. aphanidermatum and R. arrhizus. Among soil specifications, only soil saturation percent had a weak relationship with disease severity and other factors showed no distinct relation with disease symptoms. Figure 1 shows distribution of the fungi involved in sugar beet root rot inKermanshah province.