Insect-fungal infestation of stored grains of pearl millet and its impact on aflatoxin production

Five different varieties of pearl millet Pennisetum typhoides (Burm. f) Stapf and Hubb. viz., ICMH-451, ICMP-501, ICTP-8203, WCC-75 and high yielding composite variety ICMV-155 were collected after 6 months of storage to study the mycoflora and insect pests associated with storage grains in relation to aflatoxin production. Altogether 35 fungal species representing 14 genera were reported from the storage seed samples procured from kharif crop (rainy season) whereas 30 species belonging to 20 genera were reported from rabi (post rainy season) crop. The highest fungal infestation was observed in ICMH-451 variety followed by ICTP-8203, ICMP-501 and WCC-75 whereas least contamination was observed in ICMV-155 variety. With the increase in storage period, the population of Aspergillus flavus and A. niger also increased. Most of the Penicillium species were reported at later stages. A total of 7 insect species belonging to 6 genera were isolated from the seed samples collected after 6 months of storage. Among the insect pests isolated, Tribolium castaneum, Rhizopertha dominica, Corcyra cephalonica and Sitotroga cerealella, were considered as serious pests because of their high incidence and severe grain damage. Higher levels of aflatoxin contamination were reported in the kharif seed samples. The four major types of aflatoxins were reported from the kharif seed samples whereas aflatoxin G, was not observed in any variety from rabi seed samples. The relationship between aflatoxin contamination and the grains with insect damage clearly revealed that the seed samples with insect damage contain greater amounts of aflatoxins. Lowest percentage of aflatoxin contamination with meagre amounts was reported in only 0%-15% insect damaged grains.