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 toxin formation in the presence of Aspergillus flavus, Penicillium verrucosum, and Hyphopichia burtonii were studied at 20 and 30 degrees C and at 0.97, 0.95 or 0.90 aw during 3 weeks' incubation. Colonization of grain was assessed from frequency of seed infection and numbers of colony forming units (cfu) produced and by observation of hyphal extension on the grain surface from germinating spores while concentrations of T-2 toxin were determined by enzyme-linked immunosorbent assay using monoclonal antibodies. Germination of F. sporotrichioides spores was unaffected by the presence of other species under all conditions. However, subsequent colonization of barley grain by F. sporotrichioides was either completely inhibited or markedly decreased by the the presence of other fungi irrespective of the aw, temperature or competing species involved. T-2 toxin production occurred only at 20 degrees C and 0.97 or 0.95 aw, and mostly within the first 7 days: production of T-2 toxin by F. sporotrichioides was significantly greater in the presence of A. flavus and P. verrucosum throughout the 3-week incubation period under most conditions. T-2 toxin production was only slightly decreased by the presence of H. burtonii, despite the apparent lack of growth of F. sporotrichioides.