Biological and molecular characterization of a non conventional PVY variant

PVY is the best described and the second most damaging potato-infecting virus. It belongs to the family Potyviridae and is the type species of the genus Potyvirus. PVY is distributed worldwide and is also an important pathogen in other crops such as tomat o, pepper (Capsicum sp.) and tobacco. PVY can be divided into the following strain groups: O, N and C based on the responses observed in key potato cultivars. Within these strain groups isolates that induce tuber necrosis have been placed into the NTN sub group. During the year 2006, Bioforsk was contacted by the Norsk Landbruksrådgiving (NLR) regarding some drastic symptoms observed in potato tubers in many of the fields located in the region of Grimstad. These symptoms consisted of surface cracking, acc ompanied by tuber malformation and weakening of the roots. Preliminary studies, in collaboration with farmer advisors from NLR, indicate that the casual agent for these symptoms is PVY. These disease symptoms caused by PVY have also been observed sporadic ally by scientists in Peru, the Netherlands, and the USA. These symptoms, linked to the emergence of new PVY isolates, could lead to serious reductions in crop yield and quality. Early detection of infected plant material and the production of seed potato es free of this PVY variant are two major objectives in the strategy for controlling this virus. In addition, accurate diagnostic tools are required for identifying isolates that can cause tuber cracking. A prerequisite for the development of such tools i s the identification of the molecular determinants for viral pathogenicity. The following proposal is a joint effort between INRA (France) and Bioforsk to initiate comprehensive research on this new uncharacterized PVY isolate.