Mycoflora and mycotoxins of sunflower [Helianthus annus L] seeds in Egypt II Sterigmatocystin production by thermophilic [or thermotolerant] fungi

ABSTRACT

Fourteen species and 4 varieties which belong to 10 genera were collected from 36 sunflower seed samples using dilution-plate method on 1% glucose-Czapek's agar at 45°C. Aspergillus [7 species] and Mucor [1 species] were the most prevalent genera. From the preceding genera A. fumigatus, A. nidulans and M. puscillus were extremely dominant. Fifteen isolates which belong to the previous species [A. nidulans and nidulans var. lates] were screened for the production of sterigmatocystin at 28 and 45°C. Thin-layer chromatographic analysis [TLC] revealed that 4 isolates belonging to A. nidulans were positive for the toxin production at 28°C, but none of these isolates tested produced any detectable amount of sterigmatocystin when grown at 45°C. A suitable liquid medium for sterigmatocystin-producing fungi was formulated. Maximum production of sterigmatocystin was obtained at pH 5 and after incubation for 7 days at 28°C using surface cultivation