Mycoflora and Fusarium toxins of three types of corn grains in Egypt with special reference to production of trichothecene-toxins.

Sixty three species and 2 varieties which belong to 21 genera of fungi were isolated from corn grains (53 + 2, 36 + 1 and 34 species belonging to 19, 13, and 12 genera from white, yellow and popcorn, respectively). Aspergillus (15 species), Penicillium (17) and Fusarium (4) were the dominant genera isolated from the three types of corn. Of four species of Fusarium, F. moniliforme was the dominant species. F. oxysporum and F. solani were detected in all the three substrates, whereas F. subglutinans was isolated exclusively from yellow corn. A biological assay (brine shrimp larvae) and chemical analysis (TLC, UV spectrophotometery and NMR spectroscopy) of chloroform extracts proved that 7 out of 78 samples were toxic. Diacetoxyscirpenol (4 samples, 98.4-128.4 micrograms/kg corn), T-2 toxin (4 samples, 72.8 to 130.4 micrograms/kg) and zearalenone (7 samples, 22.6 to 80.4 micrograms/kg) were detected, whereas 90% methanol-water re-extracts revealed that 3 out of 78 samples were toxic due to presence of fusarin C (1 sample, 76.8 micrograms/kg) in addition to an unidentified toxic factor (3 samples). Of 22 Fusarium isolates (F. moniliforme, F. oxysporum, F. solani and F. subglutinans; 10,5,5 and 2 isolates, respectively grown on corn grains, the chloroform extracts of 6,3,3 and 1 isolates were toxic to brine shrimp larvae. Based on chemical analysis, diacetoxyscirpenol (10/22 isolates; 9.8 - 78.6 micrograms/g dry corn grains), T-2 toxin (5/22; 20.8 - 60.4 micrograms/g), HT-2 toxin (3/22; 12.4 - 18.6 micrograms/g) and zearalenone (13/22; 9.8 - 38.4 micrograms/g) were identified.(ABSTRACT TRUNCATED AT 250 WORDS)