Aflatoxin formation and varietal difference of cow pea (Vigna unguiculata (L.) Walp.) and garden pea (Pisum sativum L.) cultivars.

Different cultivars of cow pea and garden pea seeds were surveyed for susceptibility or resistance towards the toxigenic and aflatoxin-producing mould (Aspergillus flavus IMI 102135). The results show that aflatoxin production varied among the different cultivars of both cow pea and garden pea. Morphological and histological characters of the different cultivars tested did not show any relation between colour, shape and size of seeds and the amount of aflatoxin produced. The chemical analysis of the different constituents obtained from both seed coats and seed kernels with susceptible, partially resistant and resistant cow pea and garden pea cultivars revealed that the resistant cultivars of cow pea (namely: Balady cultivar) and garden pea (namely: Melting Sugar cultivar) contained lower levels of sodium and higher levels of phosphate and potassium.

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)

Natural occurrence of mycotoxins in different spices in Egypt.

A total of 120 different samples belonging to 24 kinds of species collected from different places at Assiut Governorate (Egypt) were examined for the natural occurrence of mycotoxins. TLC analysis of spice extracts revealed the presence of aflatoxins (8-35 micrograms/kg) in 16 samples of anise, black pepper, caraway, black cumin, fennel, peppermint, coriander and marjoram, sterigmatocystin (10-23 micrograms/kg) in ten samples of red pepper, caraway, cumin and marjoram and citrinin (8-12 micrograms/kg) in two samples of black cumin, while ochratoxin A and zearalenone could not be detected.

Effect of four pesticides on aflatoxin production by Aspergillus flavus IMI 89717.

The effect of three fungicides (Vitavax-Captan, Rizolex-T and Sumisclex) and one insecticide (Actellic), when incorporated into liquid medium or applied to corn grains and sunflower seeds, on the production of aflatoxin by A. flavus IMI 89717 was tested. In liquid medium, aflatoxin production was inhibited by 27%, 82%, 100% and 100% when Vitavax-Captan was added at 10, 25, 50 and 100 ppm, respectively. Sumisclex reduced to some extent the production of total aflatoxin, while Rizolex-T and Actellic did not affect quantitatively the mycotoxin production. Rizolex-T proved to be the most effective pesticides tested on aflatoxin production on both corn-grains and sunflower seeds, while Vitavax-Captan was the second most effective pesticide. Both Sumisclex and Actellic did not inhibit aflatoxin production on either corn grains or sunflower seeds at the levels tested.

Survey of mycoflora and mycotoxins in Egyptian soybean seeds.

After four months in commercial storage, 100 soybean samples from different places of Egyptian Governorates were assayed for filamentous fungal growth at two incubation temperatures (28 and 45 degrees C). 73 species and 8 varieties belonging to 32 genera were isolated by the dilution plate method. At 28 degrees C, the common species were Aspergillus flavus, A. fumigatus, A. niger and A. alutaceus, followed by A. terreus, Penicillium chrysogenum, P. citrinum, Mucor hiemalis, M. racemosus, Emericella nidulans, Rhizopus stolonifer, Nectria haematococca and Scopulariopsis brevicaulis. At 45 degrees C, A. fumigatus was the dominant species followed by Rhizomucor pusillus, Emericella nidulans and Neosartorya fischeri. Penicillium which was one of the most abundant genus at 28 degrees C, absent at 45 degrees C. The seeds were assayed for aflatoxin, ochratoxin A, sterigmatocystin, T-2 and zearalenone by thin layer chromatographic analysis. Aflatoxin was detected in 35% of soybean seed samples (5-35 micrograms/kg). The other mycotoxins were not detected.

Mycotoxin production on different cultivars and lines of broad bean (Vicia faba L.) seeds in Egypt.

One hundred different cultivars and lines of broad bean (Vicia faba L.) seed samples were inoculated with Aspergillus flavus Link (CMI 102135) to determine varietal differences which may support or resist aflatoxin production. Thin-layer chromatographic analysis of the chloroform extracts of the different seed samples revealed that 11 cultivars/lines were highly resistant to seed invasion and aflatoxin production while 9 cultivars/line showed partial resistance. The remaining 80 samples were susceptible to the establishment of A. flavus and aflatoxin accumulation. All the resistant cultivars/lines seed samples were inoculated also with three local isolates of fungi namely; Stachybotrys chartarum (Ehrenb. ex Link) Hughes, Aspergillus ochraceus Wilhelm, and Fusarium oxysporum Schlecht. The resistant seed samples were also resistant for colonization with these fungi and mycotoxin formation.

Survey of the mycoflora and mycotoxins of cotton seeds and cotton seed products in Egypt.

Thirty-nine species and 16 fungal genera were isolated from Egyptian cotton seeds, cotton seed meal and cotton seed cake on 1% glucose-Czapek's agar medium incubated at 28 degrees C. Aspergillus was the most frequent genus and it emerged in 87-100% of the samples contributing 70-98% of total fungi in the three substrates tested. The most common species were A. niger, A. flavus, A. fumigatus, A. terreus and Rhizopus stolonifer; A. niger, A. fumigatus and Penicillium corylophilum; and A. niger, A. flavus, A. terreus, A. nidulans and Rhizopus stolonifer, respectively. Cotton seeds and cotton seed products were naturally contaminated by aflatoxin B1 and B2. About 16% of the different substrates tested were positive for aflatoxin contamination. No citrinin, ochratoxin A, patulin, sterigmatocystin, diacetoxyscirpenol, T-2 toxin or zearalenone were detected in the samples assayed.

Mycoflora and trichothecene toxins of paddy grains from Egypt.

120 species and 38 genera were collected from 64 samples of paddy grains on glucose- and cellulose-Czapek's agar at 28 degrees C. The total count of glycophilic and cellulose-decomposing fungi fluctuated between 216-29760; and 124-11320 colonies/g paddy grains on the two media, respectively. On glucose agar, the most common species were Aspergillus niger, A. flavus, A. sydowi, A. terreus, A. fumigatus, A. ochraceus, Penicillium chrysogenum, P. corylophilum, Fusarium oxysporum, Alternaria alternata, Cladosporium cladosporioides, Trichoderma viride and Mucor racemosus. On cellulose agar with pH 5.5 & 8.0, the most prevalent fungi were Stachybotrys chartarum, S. bisybi, Aspergillus niger, A. flavus, Fusarium oxysporum, Alternaria alternata, Drechslera sativus and Acremonium strictum. Extracts from 64 paddy samples were tested against brine shrimp larvae (Artemis salina). Of these 9 displayed varying degrees of toxicity. Trichothecene-toxins were detected in the extracts of three paddy samples only. Diacetoxyscirpenol and T-2 toxin were detected in two samples and only T-2 toxin in the other.

Screening of zearalenone-producing Fusarium species in Egypt and chemically defined medium for production of the toxin.

296 isolates of Fusarium spp. from 100 samples of ccereal grains were examined for their ability to produce zearalenone on liquid culture medium. Thin layer chromatographic analysis revealed that the mycotoxin was detected from 45 isolates, (F. oxysporum), 36; F. moniliforme, 8; and F. equiseti, one isolate). A suitable liquid medium and some optimal conditions for the biosynthesis of zearalenone were reported. Glutamine and riboflavin stimulated the production of the toxin. The maximum amount of zearalenone appeared at pH 7, after 12 days of incubation at 20 degrees C.

Contribution to the fungal flora of cereal grains in Egypt.

30 genera and 77 species, in addition to 4 varieties were isolated from 25 samples of each of barley, wheat, maize and sorghum grains collected from different places in Egypt. The broadest spectrum of genera and species was recorded in wheat (25 genera and 59 species + 4 varieties) followed by barley (21 genera and 52 species + 2 varieties), sorghum (14 genera and 33 species + 2 varieties) and maize grains (11 genera and 29 species + 2 varieties). Aspergillus, Fusarium, Penicillium, and Rhizopus were the most common genera in the four grains, except maize where Penicillin emerged in low frequency. Aspergillus was the main component of the fungal flora of the four grains and contributed 79-94.4% of the gross total count of fungi. From the preceding genera A. niger, A. flavus, A. fumigatus, F. oxysporum, P. chyrsogenum, P. corylophilum, P. notatum and R. stolonifer were the most frequent.

Some cultural conditions that control production of verrucarin J, a cytotoxic metabolite of Stachybotrys chartarum.

A suitable chemically defined culture medium was selected and some optimal conditions for the biosynthesis of the highly cytostatic and antifungal compound verrucarin J were reported. Medium of the following composition was favourable for the production of verrucarin J by Stachybotrys chartarum: sucrose, 50; NaNO3, 2.0; KH2PO4, 1.0; MgSO4, 0.5; KCl, 0.5; leucine, 1.0 and FeSO4, 0.01 (g/l of distilled water). Biosynthesis of verrucarin J was maximal (11.8 mg/l) at pH 6.5-7.0 and after incubation for 14 days at 25 degrees C.

Toxigenic fungi isolated from Roquefort cheese.

To evaluate the potential for mycotoxin production by fungi contaminating blue-veined cheese, as well as by the ripening fungus, Penicillium roqueforti, the fungal flora of six of local and imported brands was determined. A total of 19 fungi were isolated from the six brands tested. Fourteen of the isolates were toxic to chicken embryos. The toxigenic fungi produced the following mycotoxins: Aspergillus fumigatus, kojic acid; A. versicolor, sterigmatocystin; Penicillium roqueforti, penicillic acid and unidentified toxic metabolites.

Toxigenic Aspergilli isolated from different sources in Egypt.

45 cultures of Aspergillus, belonging to 25 species isolated from different sources in Egypt, were tested for toxicity to chicken embryos and to Bacillus megaterium growth. Mycotoxins were detected by TLC analysis. 30 isolates out of 45 exhibited toxicity. 3 isolates were recorded as high-toxin producers. (A. egyptiacus, A. carneus and A. terricola). The 2 former produced unknown toxins, while A. terricola produced aflatoxins (B1, B2, G1 and G2). Aflatoxins production by A. terricola is reported for the first time.

The 11alpha and 17alpha-progesterone hydroxylases of Rhizopus nigricans NRRL 1477.

Differential induction of cultures of Rhizopus nigricans indicated that hydroxylation of progesterone at the 11alpha- and 17alpha-positions is due to two separate enzymes. This is supported by the finding that 11alpha- and 17alpha-hydroxylating activities are separated by differential centrigufation of cell-free extracts. The feasibility of introducing a hydroxyl group at the 11alpha- or 17alpha-position of hydroxylated progesterone derivatives was tested.