THE EFFECTS OF FUNGAL COMPETITION ON COLONIZATION OF BARLEY-GRAIN BY FUSARIUM SPOROTRICHIOIDES ON T-2 TOXIN FORMATION

Colonization of barley grain by Fusarium sporotrichioides and T-2 toxi n formation in the presence of Aspergillus flavus, Penicillium verruco sum, and Hyphopichia burtonii were studied at 20 and 30 degrees C and at 0 . 97, 0 . 95 or 0 . 90 a(w) during 3 weeks' incubation. Colonizat ion of grain was assessed from frequency of seed infection and numbers of colony forming units (cfu) produced and by observation of hyphal e xtension on the grain surface from germinating spores while concentrat ions of T-2 toxin were determined by enzyme-linked immunosorbent assay using monoclonal antibodies. Germination of F. sporotrichioides spore s was unaffected by the presence of other species under all conditions . However, subsequent colonization of barley grain by F. sporotrichioi des was either completely inhibited or markedly decreased by the prese nce of other fungi irrespective of the a(w), temperature or competing species involved. T-2 toxin production occurred only at 20 degrees C a nd 0 . 97 or 0 . 95 a(w), and mostly within the first 7 days: producti on of T-2 toxin by F. sporotrichioides was significantly greater in th e presence of A. flavus and P. verrucosum throughout the 3-week incuba tion period under most conditions. T-2 toxin production was only sligh tly decreased by the presence of H. burtonii, despite the apparent lac k of growth of F. sporotrichioides.