MYCOFLORA AND FUSARIUM TOXINS OF 3 TYPES OF CORN GRAINS IN EGYPT WITHSPECIAL 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 belongi ng to 19, 13, and 12 genera from white, yellow and popcorn, respective ly). Aspergillus (15 species), Penicillium (17) and Fusarium (4) were the dominant genera isolated from the three types of corn. Of four spe cies of Fusarium, F. moniliforme was the dominant species. F. oxysporu m and F. solani were detected in all the three substrates, whereas F, subglutinans was isolated exclusively from yellow corn. A biological a ssay (brine shrimp larvae) and chemical analysis (TLC, UV spectrophoto metery and NMR spectroscopy) of chloroform extracts proved that 7 out of 78 samples were toxic. Diacetoxyscirpenol (4 samples, 98.4-128.4 mu g/kg corn), T-2 toxin (4 samples, 72.8 to 130.4 mu g/kg) and zearalen one (7 samples, 22.6 to 80.4 mu g/kg) were detected, whereas 90% metha nol-water re-extracts revealed that 3 out of 78 samples were toxic due to presence of fusarin C (1 sample, 76.8 mu g/kg) in addition to an u nidentified toxic factor (3 samples). Of 22 Fusarium isolates (F. moni liforme, F. oxysporum, F. solani and F. subglutinans; 10, 5, 5 and 2 i solates, respectively) grown on corn grains, the chloroform extracts o f 6, 3, 3 and 1 isolates were toxic to brine shrimp larvae. Based on c hemical analysis, diacetoxyscirpenol (10/22 isolates; 9.8-78.6 mu g/g dry corn grains), T-2 toxin (5/22; 20.8- 60.4 mu g/g), HT-2 toxin (3/2 2; 12.4-18.6 mu g/g) and zearalenone (13/22; 9.8-38.4 mu g/g) were ide ntified. Analysis of 90% methanol-water extracts proved that 4 and 1 i solates of F moniliforme and F, oxysporum, respectively were toxic wit h detection of fusarin C (36.4-38.6 mu g/g), moniliformin (8.9-24.8 mu g/g) and an unidentified toxic factor (2, 3, and 3 isolates, respecti vely). The optimum moisture content, temperature and incubation period for DAS production (195 mu g/g) by Fusarium tricinctum (Z 90-410) on white corn grains were 60% M.C., 20 degrees C and 16 days, whereas 26% M.C., 15 degrees C and 6 days were the lowest limits for DAS producti on.