Studies on some cowpea cultivars: II - suitability for aspergillus flavus growth and Aflatoxin production

Abstract

Sixteen mycotoxin-free seed cultivar samples of cowpea (Vigna unguiculata (L.) Walp.) were inoculated with spores* of Aspergillus flavus Link (IMI 89717) to determine varietal differences in terms of aflatoxin production. Thin-layer chromatographic analyses of chloroform extracts of the colonized seeds revealed that three cultivars were highly resistant and not shown aflatoxin accumulation while 8 cultivars showed partial resistance. The remaining 5 samples were highly susceptible to the establishment of A. flavus and aflatoxin accumulation. The results did not show any relationship between morphological characters (seed colour, shape & size) or testa thickness and the amount of aflatoxin produced on the different cowpea cultivars. The results also revealed the absence of significant variation in either total nitrogen or magnesium contents of the susceptible, partially resistant and highly resistant cultivars. Calcium, potassium and total phosphate contents of both testas and kernels of the susceptible seeds were low as compared to those of partially and highly resistant seeds; and vice versa with sodium and zinc contents.