No abstract

Hypersensitive resistance (HR) is an eYcient defense strategy in plants that restricts pathogen growth and can be activated during host as well as non-host interactions. HR involves programmed cell death and manifests itself in tissue collapse at the site of pathogen attack. A novel hypersensitivity gene, Ny-1, for resistance to Potato virus Y (PVY) was revealed in potato cultivar Rywal. This is the Wrst gene that confers HR in potato plants both to common and necrotic strains of PVY. The locus Ny-1 mapped on the short arm of potato chromosome IX, where various resistance genes are clustered in Solanaceous genomes. Expression of HR was temperature-dependent in cv. Rywal. Strains PVY O and PVY N , including subgroups PVY N W and PVY NTN , were eVectively localized when plants were grown at 20°C. At 28°C, plants were systemically infected but no symptoms were observed. In Weld trials, PVY was restricted to the inoculated leaves and PVY-free tubers were produced. Therefore, the gene Ny-1 can be useful for potato breeding as an alternative donor of PVY resistance, because it is eYcacious in practice-like resistance conferred by Ry genes.

Potato mop-top virus (PMTV

No abstract

Three potato virus Y isolates, representatives of distinct PVY groups, identified in potato fields in northern Poland were submitted to biological and molecular analysis. Phenotypically, two isolates, PVYN-Ny and PVYN-Wi, belong to the necrotic strain and the third one (PVYO-LW) to the common strain. PVYN-Wi, however, did not react with monoclonal antibodies directed against the necrotic strain isolates which recognise PVYN-Ny. To characterise the isolates, coat protein genes were sequenced and compared with sequences from databases. The necrotic PVYN-Wi isolate showed 99% amino acid homology with the common one-PVYO-LW and significantly differed from the second necrotic isolate (PVYN-Ny). Sequence based homology matrix and phylogenetic analysis lead to classification of PVYN-Ny into group I, encompassing solely necrotic strain isolates, whereas PVYN-Wi falls into a phenotypically heterogeneous group II. The sequence analysis allowed for identification of putative group I-specific epitopes. 3'NTR (non-translated region) sequences were identical for PVYN-Wi and PVYO-LW. The 5'NTR, P1 gene, coat protein gene and 3'NTR sequences of the common (PVYO-LW) and the necrotic (PVYN-Wi) isolates are 99-100% homologous. This suggests that tobacco veinal necrosis determinants are located outside the 3' and 5' terminal sequences of the PVY genome.