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A novel strain of Potato virus Y from tomato
M. CHIKH-ALI (1), D. Vander Pol (1), O. V. Nikolaeva (1), M. J. Melzer (2), A. V. Karasev (3). (1) University of Idaho, Moscow, ID, U.S.A.; (2) University of Hawaii, Honolulu, HI, U.S.A.; (3) Univ of Idaho, Moscow, ID, U.S.A.

<i>Potato virus Y</i> (PVY) exists as a complex of strains that display a range of hypersensitive resistance (HR) responses in potato cultivars carrying <i>N</i> genes. The <i>Nc<sub>tbr</i></sub> gene, which has been mapped to chromosome IV of potato, confers HR against the PVY<sup>C</sup> strain. Isolates from the PVY<sup>C</sup> strain have become very rare in potato, while they still remain common in pepper and tomato, and the reasons for this are not fully understood. Here, an isolate of PVY, PVY-H, collected from tomato plants exhibiting mosaic, leaf deformations, and stunting, was subjected to biological and molecular characterization to gain insight into the epidemiology of PVY and its interactions with the <i>N</i> genes in potato. Host range studies indicated that PVY-H triggered the <i>Nc<sub>tbr</i></sub> gene in potato cultivars ‘King Edward’ and ‘Maris Bard’ inducing HR, typical of PVY<sup>C</sup> strain, and was unable to systemically infect potato. The whole genome of PVY-H was sequenced, and found to be only 91% identical to the genome of isolate PRI-509 (strain PVY<sup>C</sup>), with identities to other strains of PVY, e.g. PVY<sup>N</sup>, PVY<sup>NA-N</sup>, PVY<sup>O</sup>, PVY<sup>O</sup>-O5, and Chile3, ranging between 82-87%. Based on these host range and sequence data, PVY-H may represent a novel strain of PVY.

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