Inhibition of aflatoxin production inAspergillus flavus infected cotton bolls after treatment with neem (Azadirachta indica) leaf extracts

Abstract

In separate treatments, a spore suspension ofA. flavus (control), an aqueous leaf extract of the subtropical neem tree plus a spore suspension ofA. flavus, or an aqueous neem leaf extract followed by anA. flavus spore suspension were injected 48 hr later onto the surfaces of locks of developing cotton bolls (30-day post anthesis). Thirteen days after the treatments, the seeds from the locules were harvested and both fungal growth and aflatoxin production were determined. Fungal growth was unaffected by the treatments but the seeds from locules receiving both neem leaf extracts andA. flavus simultaneously exhibited 16% inhibition of aflatoxin production, while the seeds in locules receivingA. flavus spores 48 hr after neem extract was added exhibited >98% inhibition in aflatoxin production. Neem leaf extracts contain an aflatoxin inhibiting factor, however, the neem leaf extract may need to translocate from the fibrous locule surface to the seed, prior to the fungal inoculation, for maximal effect.