Fungal contamination, natural occurrence of mycotoxins and resistance for aflatoxin accumulation of some broad bean (Vicia faba L.) cultivars.

Abstract

Using glucose-Czapek's and 10% NaCl glucose-Czapek's agar media incubated at 28 +/- 2 degrees C, nine genera and 18 species were identified from 10 different cultivars seed of broad bean. Aspergillus and Penicillium were the most common genera on the two types of media used. The most common fungal species were Aspergillus flavus, A. niger, A. tamarii and Penicillium chrysogenum. Thin-layer chromatographic analysis indicated that seeds of one cultivar only was naturally contaminated with aflatoxins B1, B2, G1 and G2. Nine mycotoxin-free cultivars of broad bean were examined for resistance or susceptibility for aflatoxin production when inoculated by Aspergillus flavus IMI 89717. Results obtained revealed that seeds of two cultivars were highly resistant, two cultivars showed partial resistance and the remaining were susceptible to the establishment of A. flavus and aflatoxin accumulation. The results did not show any relationship between morphological characters (colour, shape and size) and the amount of aflatoxin produced on the different broad bean seed cultivars. Also the results reveal absence of significant variation in the total nitrogen of the highly susceptible, partially resistant and highly resistant groups of broad bean seeds examined. Mean values of calcium, total phosphate and potassium of both seed coat and seed kernel of the susceptible seeds were low as compared to those of partially and highly resistant seed cultivars. The susceptible seeds contained higher levels of magnesium, zinc and sodium while the resistant seeds contained lower ones.