Ankara University, Faculty of Agriculture, Department of Plant Protection, 06110 Ankara, Turkey

Background and objectives
Rhizomania is the major problem of sugar beet cultivation in Turkey. It was first observed in 1987, but identified as beet necrotic yellow vein virus (BNYV) in 1992 [1]. Since then, it has been distributed mainly on the Black Sea coast and Thrace. BNYV is a member of the Furovirus genus and its vector is a plasmodiophoraceous fungus, Polymyxa betae. Many viruliferous and non-viruliferous P. betae isolates were detected from soil according to the presence or absence of BNYV on bait sugar beet seedlings in Turkey.

Materials and methods
A rhizomania-infected sugar beet which was positive against BNVV IgG in an ELISA test was taken from Tokat province. Rootlets were washed and the presence of P. betae was investigated by light and electron microscope observations [2].

Results and conclusions
Plasmodium, cystosori and zoosporangium of P. betae were easily seen in light microscope observations. Fungal thallus, plasmodium, cystosori, zoospore and zoosporangium were present in ultra-thin sections of infested sugar beet rootlets under the electron microscope. The fungus had caused great damage in rootlet tissues. No virus particles were detected in fungal structures due to the plasmodial content.

1. Vardar B, Erkan S, 1992. Journal of Turkish Phytopathology 21, 71-77.
2. Abe H, Tamada T, 1986. Annals of the Phytopathological Society of Japan 52, 235-247.