Poster Session: Host Resistance

269-P

Identifying resistance to Sclerotinia stalk and root rot in perennial sunflower germplasm.
C. BLOCK (1), L. F. Marek (2), T. J. Gulya (3)
(1) USDA-ARS, Ames, IA, U.S.A.; (2) Iowa State University, Ames, IA, U.S.A.; (3) USDA-ARS, Fargo, ND, U.S.A.

The objective of the research was to identify resistance to Sclerotinia stalk and root rot in perennial sunflower species from the USDA germplasm collection. Two diploid species, Helianthus grosseserratus and H. salicifolius, and four hexaploid species, H. californicus, H. pauciflorus, H. resinosus, and H. tuberosus were evaluated in greenhouse trials. Screening was conducted by placing Sclerotinia-infested millet into individual cells of plastic flats and transferring one seedling with 6 to 8 leaves into each cell. Plants were monitored for days to permanent wilt and accessions were ranked on the basis of plant survival after 21 days. All of the perennial species showed remarkable resistance. From the 144 accessions tested across six species, 106 accessions had 90% or more surviving plants. By comparison, the most resistant hybrid check, Croplan 305, ranged from 40-55% plant survival and the susceptible check ranged from 0-5% survival. Forty-four accessions had 100% plant survival including 7 of 10 accessions from H. californicus, 8 of 14 from H. resinosus, 7 of 14 from H. salicifolius, 9 of 38 from H. tuberosus, and 13 of 37 from H. grosseserratus. Five of 31 H. pauciflorus accessions had 95% or better plant survival, with the highest at 98%. The results demonstrate that perennial sunflowers may be a potentially valuable source of Sclerotinia resistance genes for improving cultivated sunflower.