Submitted to: Canadian Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 10, 1996
Publication Date: N/A
Interpretive Summary: Yeast microbes are common in maize ears damaged by insects or rotted by mycotoxin-producing molds. Some yeasts produce so-called "killer proteins" that prevent the growth of other yeasts and may also prevent the growth of mycotoxin-producing molds. This study characterized the yeast community of maize from a field in central Illinois and determined which maize yeasts produce killer proteins. These maize yeasts are candidates for biological control of molds and mycotoxins in damaged maize ears.
Technical Abstract: Microflora in woundsites of pre-harvest 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 of filamentous fungi. As little data are available about the yeasts occurring on maize from the US 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 (10 Log N/g values). The majority of the yeasts were Candida guilliermondii (approx. 55%), Candida zeylanoides (24%), Candida shehatae (11%), and Debaryomyces hansenii (3%). Also present were Trichosporon cutaneum, Cryptococcus albidus var. aerius, and Pichia membranaefaciens. The occurrence of killer-yeasts was also evaluated. Killer-yeasts detected were identified as Trichosporon cutaneum and Candida zeylanoides. These were also 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 membranaefaciens) 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. These properties are of importance in relation with insect attraction to pre-harvest ears of maize.