Standpoint about the spread of potato wart disease in bulgaria (synchytrium endobioticum); pathotypes identification and testing of potato varities for resistance

Potatoes are one of the most important crops worldwide. Potato wart disease is major quarantine disease, caused by the Chytridiomycete Synchytrium endobiticum (Shilb.) Perc. The typical symptoms are tumour-like outgrowths arising near meristematic tissues (e.g. buds on tubers). The foci of potato wart disease occur only in the mountainous parts of Bulgaria. The pathogen has been detected in private gardens, or small farms with out crop rotation, which do not share with seed potato production.
The prime pathway for spread is trade of potato tubers, which may be infected internally, or may carry adhering soil. The resting spores of S. Endobioticum are able to persist in the soil over 40 years. For infection of potato plants is need soil infection level below 1 sporangium per g soil. First occurrence of pathogen in Turkey, Greece and Bulgaria showed, that the pathogen has well adapted to continental climate. The pathotypes 1 (D1), 2(G1), 6(O1) and 18 (T1) are the most widespread in the EPPO region.
National Phytosanitary regulations have been applied in the infected regions, to prevent spread of the fungus.
The experimental work for testing of pathotypes and potato cultivars for resistance, was carried out with field tests and Laboratory tests (Spieckermann and Glynne-Lemmerzahl methods), according to Diagnostic protocol of EPPO PM 7/28(1). The Glynne-Lemmerzahl method is based on the infection of young sprouts by zoocpores directly produced by summer sporangia of fresh wart tissue. This method is high reliable and efficient.
Pathotypes in the infected regions have been identified with different isolates: Podvis correspond with Nevsehir1, which is mix of pathotypes 6(O1) and 18(T1) and isolate Barutin, identical with new pathotype 38Nevsehir. Based on the results obtained with laboratory tests, it was concluded that the pathotype in the field in Prodanovtsi was probably 8(F1). Identified resistant potato varieties to isolate Podvis and Barutin are not commercial significance for Bulgaria.
Field and pot tests with variants of Glauconit and sweet corn for crop rotation showed decreasing the number of viable winter sporangia. We need то make more precise the doses per xa.