Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/18/2006
Publication Date: 1/20/2006
Citation: Rashid, K.Y., Seiler, G.J. 2006. Epidemiology and resistance to Sclerotinia head rot in wild sunflower species [abstract]. Sclerotinia Initiative Annual Meeting, January 18-20, 2006, Bloomington, MN. p. 24. Available: http://www.whitemoldresearch.com/html/abstractdetails2.cfm?Research_ID=130 Interpretive Summary:
Technical Abstract: Field trials were conducted in 2002 to 2005 to understand the epidemiology of the Sclerotinia infection in wild sunflower heads and stems, to establish methodology for assessing wild sunflower germplasm, and to identify sources of resistance. In 2002-2003, 96 accessions of perennial wild sunflower species of Helianthus maximiliani and H. nuttallii were tested in a four replicated randomized complete block design trial with various inoculum types, inoculation at three growth sages, and using three head coverings. Ground Sclerotinia infected millet seed and ascospores inoculated at the mid-flowering stage and covered with brown paper bags which proved to be the most appropriate method to create disease epidemics to differentiate between susceptible and resistant genotypes. In 2004-2005, 400 accessions of the perennial wild sunflower species were evaluated using the standard artificial inoculation procedure established in previous years with a combination of ascospores and ground sclerotinia-infected millet seed. Different groups of plants (5 to 10) from each accession were inoculated at the early-flowering and late-flowering stages, and were covered with light brown paper bags. The typical symptoms of Sclerotinia infection on wild sunflower plants were stem bleaching, shredding, and the formation of tiny cylindrical sclerotia inside the stems, while the heads were shriveled and dry with little or no seed set. Some changes were observed in the reaction of several accessions from year to year; however, most wild accessions identified with resistance to head rot in 2002-2003 remained resistant in 2004 and 2005. Several accessions remained healthy in the four years of testing under the various artificial inoculation methods. Such accessions are believed to have genetic resistance to Sclerotinia head rot and mid-stem infection. Present research is focusing on studying the genetics for this resistance and the transfer of the resistance genes into sunflower breeding lines for future hybrid development. These accessions will be deposited in the Plant Gene Resources Genebank of Canada, AAFC, and at the USDA-ARS Sunflower Research Unit at Fargo, ND.