Preliminary symptomathological and molecular characterization of Potato virus Y italian isolates causing potato tuber necrotic ringspot disease (PTNRD).

Potato virus Y (PVY) is one of the most damaging potato pathogens. Its strains present in nature belong to 3 main groups: N (necrotic on tobacco), 0 and C (non necrotic). Among strains of the first group, very important are those causing tuber necrosis (NTN) on some potato cultivars, which render tuber useless both as propagating seed and edible material. To avoid their spread in field it is, therefore, necessary in seed potato production to use an early diagnose method for properly roguing fields. To this purpose, we tried to set up a molecular method able to single out NTN strains. Several virus isolates were sampled from various Italian potato fields, and 15 of them resulted to be N strain as proved by both ELISA tests and mechanical inoculation on tobacco. Five PVY N isolates and 2 PVY 0 for comparison were then inoculated on 10 plants each of a sensitive potato cv (Monalisa) in the greenhouse (20± 2°C), to sort out NTN isolates. These last were characterized on a molecular basis by multiplex RT-PCR using various combinations of primer cited in literature (Weidemann and Maiss, 1996; Nie and Singh, 2003), to possibly correlate necrotic symptoms with a particular pattern in agarose gel electrophoresis. The experiments carried out were not always sufficient to discriminate between N and NTN isolates. Therefore, further tests with other strains, using also new primers combinations, are currently in progress. Nie, X., Singh, R. P., 2003. Specific differentiation of recombinant PVYN:O and PVYNTN isolates by multiplex RT-PCR. J. of Virol. Methods 113:69-77. Wedemann, H. L., Maiss, E., 1996. Detection of the potato tuber necrotic ringspot strain of potato virus Y (PVYNTN) by reverse transcription and immunocapture polymerase chain reaction. J. Plant Dis. Protec. 103: 337-345.