Submitted to: Mycotaxon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2007
Publication Date: 1/1/2008
Citation: Roberts, R.G. 2008. Alternaria roseogrisea, a new species from achenes of Helianthus annuus (sunflower). Mycotaxon. 103:21-26.
Interpretive Summary: An unidentified fungus know for more than 25 years to be associated with oilseed-type sunflower seed has been formally described and named Alternaria roseogrisea R.G. Roberts. This fungus is not known to be a pathogen of sunflower, although its known range is limited to sunflower production areas in the upper Midwestern U.S. A. roseogrisea is a member of the A. infectoria species group because of the pattern of spore production in culture and the development of long secondary spore-bearing structures during development. The fungus was named roseogrisea because it produces pinkish-gray cultures when grown on Tomato juice agar containing 6 percent sodium chloride.
Technical Abstract: Alternaria roseogrisea was isolated from the achenes of Helianthus annuus L. during studies conducted in 1983-85 to document the diversity of fungi occurring in sunflower seeds and the possible role these fungi play in degradation of oilseed quality. A. roseogrisea was reported as "Alternaria sp. 2" in this early study because there were no published descriptions in Alternaria to accommodate it, a deficiency that has persisted. More recently, cluster analyses of combined RAPD, RAMS (microsatellite) and AFLP fingerprints support the placement of A. roseogrisea within the A. infectoria species group sensu Simmons and its segregation from other members of this group. A. roseogrisea is known only from high-quality oil-type sunflower seed, and is characterized by the grayish-pink color of mature colonies on 6 percent NaCl-tomato juice agar and by the striking appearance of the very small, often one or two-celled conidia separated by secondary conidiophores that can be many times the length of and nearly as wide as the conidia themselves.