Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 4, 2007
Publication Date: August 1, 2007
Citation: Block, C.C., Gulya Jr, T.J., Marek, L.F. 2007. Greenhouse evaluation of wild sunflower species for resistance to Sclerotinia wilt [abstract]. American Phytopathological Society Annual Meeting. 97:S11. Technical Abstract: Wild sunflowers have been a frequent source of genes for disease resistance for cultivated sunflowers, but are largely unexplored in terms of resistance to Sclerotinia wilt, caused by the fungus Sclerotinia sclerotiorum. The initial goal of this project was to develop a reliable greenhouse screening method so that large numbers of plants could be evaluated relatively quickly and only the most promising material advanced to field trials. Resistant and susceptible cultivated hybrids with well-characterized field reactions were used to identify suitable screening conditions. Incubation temperature was identified as the most critical variable, as even modestly higher temperatures slowed disease development. For example, at constant 21C, 100% of the plants of a susceptible cultivar wilted and died at an average of 11 days. At constant 25C, 40% of the plants of the same cultivar showed no symptoms even after 21 days. Temperature was more important than pot size, pot shape, soil type, inoculum quantity, and inoculum placement in the pots. Evaluation efforts are focused on the annual diploid Helianthus species in the USDA sunflower germplasm collection, primarily the non-H. annuus taxa. Several accessions of Helianthus debilis and Helianthus argophyllus have shown excellent resistance in the greenhouse tests. These results are promising, but will need to be verified in field trials.