Distribution of Polymyxa betae the Vector of Sugarbeet Rhizomania in Esfahan, West Azarbaiejan and Khorasan Provinces

Polymyxa betae, the vector of the BNYVV causal agent of Rhizomania disease, is a soil-borne fungus that survives as an obligate parasite on roots of sugarbeet and other chenopodiaceae plants. It produces resistant spores (cystosori) which are able to live in soil as dormant stage and easily transmitted by soil, plant debries, and agricultural machinary. Because of the importance of the disease in sugarbeet cultivation, a survey was conducted during the years of 2001-2002 to investigate distribution of the fungal vector in soils of areas under sugarbeet growing of Esfahan, west Azarbayejan and Khorasan Provinces. The soil samples were mixed with an equal volume of sterile sand separetely and dispensed into pots. Seeds of a susceptible sugarbeet cultivar CV. P22 were sown in pots and watered weekly. To determine the infection of plants to P. betae, the roots were washed in running water and plunged in boiling lactophenol containing acid fuchsin and examined by light microscope. Results indicated that in 289 soil samples from Esfahan province, the most infection belong to, Qale-eslam area with, 45.7 percent. In 352 soil sampls of West Azarbayejan, 79 sampls were infected to P. betae. Qarah-ziaedin area, was observed the most infected area to the fungus with 31.8 Percent infection. Soil Samples from 23 regions of Khorasan province, indicated that infected to P. betae in north regions are more severe than the other regions. Infection in Chenaran, Torbatjam, Shirvan, Quchan, Fariman and Sabzevar were stimated more than 50percent. Microscopic examination showed the high potential of root infection with the fungus in the greenhouse. This attributed to the number of resting spores per 1 gram of root which were more than 480. Widespread distribution of P. betae in sugarbeet growing areas of Esfahan, West Azarbayjan and North of Khorasan provinces, Indicated that the occurrence of the Rhizomania disease in these areas is inevitable.