BIODIVERSITY OF YEASTS FROM ILLINOIS MAIZE

Microflora in wound sites of preharvest maize (including bacteria, yea sts, and filamentous fungi) may play a role in attracting insects to m aize plants and may also interact with growth and mycotoxin production by filamentous fungi. As little data are available about the yeasts o ccurring on maize from the U.S. corn belt, samples of milled maize fro m experimental plantings at the University of Illinois River Valley Sa nd Field were analyzed. Yeast counts showed slight yearly fluctuation and varied between 3.60 and 5.88 (log cfu/g maize). The majority of th e yeasts were Candida guilliermondii (approximately 55%), Candida zeyl anoides (24%), Candida shehatae (11%), and Debaryomyces hansenii (3%). Also present were Trichosporon cutaneum, Cryptococcus albidus var. ae rius, and Pichia membranifaciens. The occurrence of killer yeasts was also evaluated. Killer yeasts were detected in maize for the first tim e and were identified as Trichosporon cutaneum and Candida zeylanoides . These were able to kill some representative yeasts isolated from mai ze, including Candida guilliermondii, Candida shehatae, and Cryptococc us albidus var. aerius. Other maize yeasts (Candida zeylanoides, Debar yomyces hansenii, Pichia membranifaciens) were not affected. The major ity of yeasts found on maize were unable to ferment its major sugars, i.e., sucrose and maltose. Some (e.g., Candida zeylanoides) were not e ven able to assimilate these sugars. The importance of these propertie s in relation to insect attraction to preharvest ears of maize is disc ussed.