Inheritance of Partial Resistance to Tobacco Etch Virus and Tobacco Vein Mottling Virus in Burley Tobacco Cultivar Sota 6505. David B. Fischer, Former Graduate Research Assistant, Department of Crop Science, Box 7620, North Carolina State University, Raleigh 27695-7620. Rebeca C. Rufty, Associate Professor, Department of Crop Science, Box 7620, North Carolina State University, Raleigh 27695-7620. Plant Dis. 77:662-666. Accepted for publication 13 January 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0662.

Tobacco etch virus (TEV) and tobacco vein mottling virus (TVMV) are serious diseases of burley tobacco and are controlled most effectively by use of resistant cultivars. The inheritance of resistance to TEV and TVMV in the burley tobacco cultivar Sota 6505 and allelism with other sources of potyvirus resistance were evaluated. Crosses were made between Sota 6505 and two susceptible burley tobacco cultivars, Ky 14 and Va 528. Parental genotypes, F₁, F₂, and backcross generations to each of the parents were evaluated in randomized complete block designs for TEV resistance at Waynesville, North Carolina, and Las Varas, Nayarit, Mexico, and for TVMV resistance at Laurel Springs, North Carolina, during 1988 and 1989. Crosses were also made between Sota 6505 and TEV- and TVMV-resistant cultivars Virgin A Mutant and Havana 307 to test for allelism. Resistant × resistant crosses were evaluated for TEV resistance in a greenhouse in Raleigh, North Carolina. Plants were mechanically inoculated in the field approximately 1 mo after transplanting and in the greenhouse 1 wk after transplanting. Disease severity data were collected at topping time in the field and 1 mo after transplanting in the greenhouse. Chi-square goodness of fit tests were conducted, but simple Mendelian inheritance ratios did not fit the data for expression of resistance with either virus, possibly because of environmental effects. Generation means analysis showed that a simple additive-dominance model adequately described the data. Additivity was the major genetic effect, and there was no evidence of epistasis. The gene(s) controlling TEV resistance in Sota 6505 appears to be allelic to the virus resistance gene(s) found in resistant cultivars Virgin A Mutant and Havana 307.