Omo. Elmaghraby et al., MYCOFLORA AND FUSARIUM TOXINS OF 3 TYPES OF CORN GRAINS IN EGYPT WITHSPECIAL REFERENCE TO PRODUCTION OF TRICHOTHECENE-TOXINS, Microbiological research, 150(3), 1995, pp. 225-232
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.