Poster Session: Systematics/Evolution/Ecology-Oomycetes

97-P

Stimulation of sexual structure production by Pythium.
K. ZITNICK-ANDERSON (1), B. Nelson Jr. (1)
(1) Department of Plant Pathology, North Dakota State University, Fargo, ND, U.S.A.

Identifying Pythium species based on morphological features has been a difficult challenge for mycologists. Pythium produces many unique distinguishing traits including both asexual and sexual structures. Proper identification cannot be achieved without the presence of both structures. Previous research indicated that turf grass clippings can stimulate the production of sexual structures. The use of grass clippings to enhance production of sexual structures was investigated using tall fescue (cultivar Grande2) and Kentucky bluegrass. The method that resulted in the greatest sexual structure production was to autoclave clippings of both grass cultivars in tap water for 20 min. Then an agar plug plus mycelium from a 5-day-old culture on potato dextrose agar was placed into a 60 mm diameter petri dish with 15 ml of the autoclaved grass clipping plus the same water used to autoclave the grass. In general, sexual structures formed within 24 to 48 hr on the edges of the grass clippings, but were not observed in the agar plugs. These structures were readily visible and abundant on the grass clippings when identifying Pythium species such as P. kashmirense, P. ultimum, and P. perplexans. When glass clippings are autoclaved but removed from the water they are autoclaved in and then placed in fresh autoclaved tap water, sexual structure production was markedly reduced. The water from the autoclaved grass clippings apparently has compounds that greatly stimulate sexual structure production.