ARS | Publication request: Epidemiology and Resistance to Sclerotinia Head Rot in Wild Sunflower Species

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 30, 2009
Publication Date: May 31, 2009
Citation: Rashid, K.Y., Seiler, G.J. 2009. Epidemiology and Resistance to Sclerotinia Head Rot in Wild Sunflower Species [abstract]. 14th International Sclerotinia Workshop, May 31-June 4, 2009, Wilmington, NC.

Technical Abstract: Field trials were conducted in 2002-2008 to establish methodology for infecting and assessing the reaction of wild perennial sunflower species to sclerotinia, to understand the epidemiology of the Sclerotinia infections to wild sunflower heads and stems, and to identify sources of resistance. In 2002-2003, 96 accessions of perennial wild sunflower species Helianthus maximiliani and H. nuttallii were tested using several inoculum types and methods of inoculation. Ground sclerotinia-infected millet seed and ascospores inoculated at the mid flowering stage and covered with brown paper bags proved to be the most appropriate method to create disease epidemics. In 2004-2008, 400 accessions of these wild species were evaluated using the most effective artificial inoculation procedure with a combination of ascospores and ground sclerotinia-infected millet seed. The typical symptoms of infection were stem bleaching and shredding, the formation of tiny cylindrical sclerotia inside the stems, shriveled and dry heads with little or no seed setting. Several wild accessions were identified with resistance to head rot and mid-stem infections over the years. Present research is focusing on studying the inheritance of the genetic resistance and the transfer of the resistance genes to sunflower breeding lines for future hybrid development.