Variability of Potato Virus Y in Potato Crops in France

A collection of 221 PVY isolates\ originating from potato crops\ was characterized in order to seek the newly described PVY variants\ PVYNW and PVYZ[ Sero! logically\ 173 samples were found to contain only PVYO25 samples to contain only PVYN\ whereas 01 samples were doubly infected by both PVYO and PVYN[ All 25 isolates\ serologically PVYN!typed and 05 isolates sero! logically PVYO!typed\ induced vein necrosis on tobacco[ The latter 05 isolates reacted like a Polish standard PVYNW isolate and are probably new members of that PVY subgroup^ in the panel of samples\ they originated from potato cultivars never previously reported as infected by PVYNW and their high incidence probably indicates that they are more widespread than commonly accepted[ Indexing of 097 PVYO isolates on three potato cultivars "Desiree\ Eersteling and Maris Bard# carrying hypersensitivity resistance genes to PVYO\ PVYC and PVYZ\ respectively\ revealed the presence of various pathotypes[ Two isolates reacted as two standard isolatesdesignated PVYZE\ originating from Spain and previously suspected to be PVYZ members^ these isolates were able to overcome the hypersensitivity genes in the three potato cultivars and consequently were members of a newly recognized pathotype[ Another isolate evoked the reac! tions expected after infection with PVYZ[ SurprisinglyPVYC was only found in one sample that was doubly infected by PVYO[