Evaluation of Tobacco Accessions for Resistance to Tobaco Cyst Nematode and Wildlife
- A. J. Hayes,
- C. A. Wilkinson and
- C. S. Johnson
Control of tobacco cyst nematode (Globodera tabacum solanacearum Miller and Gray) is of major concern to growers of flue-cured tobacco (Nicotiana tabacum L.) in Virginia. A diverse geographic array of accessions including cultivars of several classes of tobacco, flue-cured type tobacco introductions, and Nicotiana species were evaluated during 1993 and 1994 in the greenhouse to identify new sources of resistance to tobacco cyst nematode (TCN). Six-week-old transplants were inoculated with 6000 TCN eggs from crushed cysts. An average of eight weeks after inoculation, a 1-g sample of root was stained and vermiform, swollen, pyriform, and adult nematodes were counted. Accessions were also evaluated for response to wildfire (Pseudomonas syringae pv. tabaci Wolf and Foster) to determine if resistance to these two pathogens was correlated. The underside of a single 10- to 15-cm leaf from 6-wk-old transplants was inoculated with a suspension of wildfire bacteria by means of a CO2 air brush. Leaves were rated for disease severity 5 d after inoculation. Several accessions had significantly reduced nematode reproduction including TI 1597, TI 1625, ‘Burley 64’, ‘MD 40’, ‘Pennbell 69’, and ‘Kutsaga Mammoth 10’. Although wildfire resistance was highly correlated with TCN resistance, some accessions had no resistance relationship to the two pathogens. Nicotiana miersii Ramy was susceptible to wildfire while supporting very low nematode populations and both TI 551 and ‘KY 190’ were resistant to wildfire but were susceptible to TCN. Evaluation of accessions for wildfire resistance may not be a reliable method of screening for TCN resistance and would result in alternate sources of TCN resistance being overlooked.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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