COLONIZATION OF BARLEY-GRAIN BY PENICILLIUM-VERRUCOSUM AND OCHRATOXIN-A FORMATION IN THE PRESENCE OF COMPETING FUNGI

Colonization of barley grain by Penicillium verrucosum and the formati on of ochratoxin A were studied, both in pure culture and when paired with Aspergillus flavus, Fusarium sporotrichioides, and Hyphopichia bu rtonii, at 20 degrees and 30 degrees C and at 0.97, 0.95 and 0.90 a(w) over a 3-week period. Grain colonization was assessed on the basis of visible molding, seed infection, and numbers of CFU and by observing hyphal extension on the grain surface by scanning electron microscopy. Ochratoxin A concentrations were assayed by enzyme-linked immunosorbe nt assay using a monoclonal antibody. Germination of P. verrucosum spo res was unaffected by the presence of other species. However, seed inf ection under most conditions was markedly decreased, relative to pure culture, by the presence of A. flavus and H. burtonii, but only slight ly by F. sporotrichioides. The number of CFU of P. verrucosum was only slightly decreased in the presence of other species under most condit ions. Generally, production of ochratoxin A by P. verrucosum was inhib ited, sometimes significantly, in the presence of A. flavus and H. bur tonii, but was changed only slightly by the presence of F. sporotrichi oides. There was occasionally temporary enhancement in ochratoxin A pr oduction with all species during the 3-week incubation period.