Inheritance of Resistance to Tobacco Cyst Nematode Globodera tabacum solanacearum

The tobacco cyst nematode [Globodera tabacum solanacearum (Miller & Gray, 1972) Behrens, 1975] is an important pathogen affecting flue-cured tobacco (Nicotiana tabacum L.) in Virginia, North Carolina, and Maryland. The resistant cultivars Coker 371 Gold and Kutsaga 110 were evaluated during 1999 and 2000 in the greenhouse to determine the mode of inheritance of resistance to the tobacco cyst nematode (TCN). Each cultivar was crossed to the susceptible cultivar K 326 and F1 progeny were backcrossed to each parent. Plants from each parent and F1, F2, BC1Ps, and BC1Pr progeny were evaluated for TCN resistance. Six-week-old transplants were inoculated with 6000 TCN eggs from crushed cysts. Eight weeks after inoculation, a 1-g sample of fibrous root was stained and vermiform, swollen, pyriform, and adult nematodes were counted. The number of cysts and eggs per 400 cm3 of soil were counted from each transplant. Generation means analyses were performed. Additive and dominance gene action play an important role in resistance to TCN in Coker 371 Gold and Kutsaga 110. F2 generation data from the Coker 371 Gold cross fit a 3:1 (resistant:susceptible) segregation ratio and BC1Ps generation data fit a 1:1 segregation ratio, indicating that resistance to TCN is conferred by a single dominant gene. A continuous range of variation was observed among the F2 progeny for the K 326 X Kutsaga 110 cross, indicating resistance in Kutsaga 110 is quantitative. TCN resistance in Coker 371 Gold and Kutsaga 110 may be derived from different sources.