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A Genetic Analysis of the Association Between Resistance to Meloidogyne incognita and a Necrotic Response to Infection by a Strain of Potato Virus Y in Tobacco. Rebeca C. Rufty, Research associate, Department of Crop Science, North Carolina State University, Raleigh 27650; E. A. Wernsman(2), and N. T. Powell(3). (2)Professor, Department of Crop Science, North Carolina State University, Raleigh 27650; (3)Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 73:1413-1418. Accepted for publication 2 May 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1413.

The genetic basis for the association between resistance to the root-knot nematode Meloidogyne incognita, and a severe vascular necrosis in response to infection by the MSNR strain of potato virus Y (PVY-MSNR) in tobacco (Nicotiana tabacum L.) was investigated. More than 15,000 F2 plants derived from root-knot resistant x root-knot susceptible crosses were inoculated with both pathogens. All plants that did not develop necrosis in response to the virus were root-knot susceptible; ie, recombination between root-knot resistance and the necrotic response to the virus was not detected. Each trait is controlled by a single, dominant gene located on chromosome G of tobacco by monosomic and nullisomic analysis. The virus-induced necrosis may be a pleiotropic response of the gene controlling root-knot resistance. Plants possessing both root-knot and PVY resistance developed little or no necrosis. PVY resistance is conditioned by a recessive gene that appears to be epistatic to the gene conditioning root-knot resistance. A search was made among Nicotiana spp. for a new source of root-knot resistance not associated with the necrotic reaction to PVY- MSNR. Nicotiana tomentosa, accession 58, was highly resistant to the nematode and appeared to be immune to the virus.