Document Type : Research Article
Genus Polymyxa, belongs to Plasmodiophoromycota Phyllum and Protozoa Kingdom. This fungus is a obligate endoparasite in the root cells of vascular plants. Since the two species of this genus, P. graminis and P. betae are both known to carry destructive viral agents to sugar beet and Poaceae. For studying the distribution of infected fields with P. betae in Razavi and Northern Khorasan provinces, 39 soil samples were taken from sugar beet fields in the two provinces. Then in Collected soils, sugar beet seeds (IC) were planted and after 5 to 7 weeks, the growing plants were removed from the soils and with using two methods (Microscopic and Nested PCR) the rate of contamination to P.betae was evaluated in different fields.The results showed that this fungus was detected in 59 percent of tested plants by Microscopic method and in 75. 3 percent of samples tested by molecular method. In planting 18 species of dominant weed seeds of sugar beet and wheat fields in contaminated soils ,the hosting possibility of these plant species were investigated by using two Microscopic and Molecular methods in the both provinces. Among these weeds Chenopodium album, Amaranthus retroflexus, A.viridis , Portulaca oleraceae and Convolvulus arvensis were hosts, and Chenopodium album and Convolvulus arvensis varieties were introduced as alternative hosts of this fungus.