Resistance to a Necrotic Strain of Potato Virus Y Among Nicotiana Species, Somatic Hybrids, and Tobacco Cultivars. J. E. BRANDLE, Agriculture Canada, Research Station, P.O. Box 186, Delhi, Ontario, N4B 2W9. L. W. STOBBS, Agriculture Canada, Research Station, P.O. Box 6000, Vineland Station, Ontario, LOR 2E0; and S. GLEDDIE, Agriculture Canada, Plant Research Centre, Central Experimental Farm, Ottawa, Ontario, K1A 0C6. Plant Dis. 79:152-154. Accepted for publication 20 October 1994. Copyright 1995 Department of Agriculture and Agri-Foods, Government of Canada. DOI: 10.1094/PD-79-0152.

Fifty-four tobacco cultivars, seven species, and four somatic hybrids were examined for resistance to a Canadian isolate of potato virus Y necrotic strain (PVYN). Four cultivars were resistant to infection: Virgin A Mutante (VAM), NC744, TN86, and PBD6. Virus was not detected in inoculated plants by enzyme-linked immunosorbent assay, electron microscopy, or back-inoculation to susceptible tobacco plants. Resistant plants were similar in appearance to the healthy uninoculated controls. A single recessive gene from VAM is believed to be common to the four resistant varieties. Havana 307, Wanda, and Wisana were tolerant to PVYN infection, exhibiting mild mosaic symptoms with or without veinal necrosis, and similar in overall growth to the healthy controls. All the registered Canadian cultivars tested were susceptible to PVYN infection. Of the species tested, Nicotiana kawakami exhibited mild symptoms and reduced virus titer and N. rustica L. var. NRT exhibited tolerance when inoculated with PVYN. No resistance or tolerance to PVYN infection was found in any of the somatic hybrids tested. These results demonstrate that genetic resistance to PVYN is present both within the tabacum genome and among its wild relatives. The utility of the sources of resistance is variable, however.