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Characterization of Potato Virus Y Resistance from Gametoclonal Variation in Flue-Cured Tobacco. Carl H. Yung, Former graduate research assistant, Department of Crop Science, North Carolina State University, Raleigh 27695; E. A. Wernsman, and G. V. Gooding, Jr. Professor, Department of Crop Science, and professor, Department of Plant Pathology, North Carolina State University, Raleigh 27695. Phytopathology 81:887-891. Accepted for publication 19 February 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-887.

A previously identified gametoclonal tobacco variant, NC 602, exhibits resistance to certain potato virus Y (PVY) strains. NC 602 was subjected to a second cycle of anther culture and colchicine treatment. The resulting doubled haploid lines were evaluated for back mutation to susceptibility and any additional mutation that might provide resistance to tobacco etch virus (TEV). The PVY resistance was stable in anther culture, and although no TEV resistance was found, three lines were identified with delayed symptom onset. NC 602 was crossed to breeding line NC 744, which contained the PVY resistance gene found in the Virgin A Mutante (VAM) (Tobacco Introduction line 1406). Maternal doubled haploid lines of this cross were screened for both resistance genes by using an array of PVY strains to distinguish genotypes. Results demonstrated that the two genes could be combined into a single genome with improved levels of resistance, thus indicating different loci for each resistance. NC 602 was also crossed to a root-knot nematode (Rk) resistant cultivar (Coker 209) in an effort to combine PVY and Rk resistance for protection against the MN strain of PVY in Rk resistant varieties. Plants were identified at the haploid level, which contained both PVY(NN) and Rk resistance, but when these plants were doubled and challenged with the PVY(MN) strain, all lines resistant to Rk showed susceptibility to the virus.