Biodiversity of yeasts from Illinois maize

Microflora in wound sites of preharvest maize (including bacteria, yeasts, and filamentous fungi) may play a role in attracting insects to maize plants and may also interact with growth and mycotoxin production by filamentous fungi. As little data are available about the yeasts occurring on maize from the U.S. corn belt, samples of milled maize from experimental plantings at the University of Illinois River Valley Sand Field were analyzed. Yeast counts showed slight yearly fluctuation and varied between 3.60 and 5.88 (log cfu/g maize). The majority of the yeasts were Candida guilliermondii (approximately 55%), Candida zeylanoides (24%), Candida shehatae (11%), and Debaryomyces hansenii (3%). Also present were Trichosporon cutaneum, Cryptococcus albidus var. aerius, and Pichia membranifaciens. The occurrence of killer yeasts was also evaluated. Killer yeasts were detected in maize for the first time and were identified as Trichosporon cutaneum and Candid zeylanoides. These were able to kill some representative yeasts isolated from maize, including Candida guilliermondii, Candida shehatae, and Cryptococcus albidus var. aerius. Other maize yeasts (Candida zeylanoides, Debaryomyces hansenii, Pichia membranifaciens) were not affected. The majority of yeasts found on maize were unable to ferment its major sugars, i.e., sucrose and maltose. Some (e.g., Candida zeylanoides) were not even able to assimilate these sugars. The importance of these properties in relation to insect attraction to preharvest ears of maize is discussed.