Efficacy of atoxigenic aspergillus flavus (aflasafe ke01) on the population of aflatoxigenic fungi and aflatoxin contamination of maize (zea mays l.) in alternate seasons in lower eastern Kenya

Abstract

Aflasafe KE01 is a biological control product comprising of four atoxigenic strains of Aspergillus flavus which are native in Kenya. This study determined the efficacy of Aflasafe KE01 on the population of aflatoxin producing fungi and aflatoxin contamination of maize in alternate seasons. Field efficacy trials were carried out in aflatoxin hot spots in Kathiani and Wote sub Counties in lower Eastern Kenya. Twenty four maize fields were selected at random in each Sub County where 12 were treated with Aflasafe KE01 while 12 were not treated. Aflasafe KE01 was broadcast in the maize fields 2-3 weeks before tussling of maize at a rate of 10kg/ha. Soil samples were collected from each field prior to application of the product and one year later; while maize samples were collected at harvest in both seasons. Aspergillus section Flavi were isolated from soil and maize grains on modified Dicloran Rose Bengal agar and identified on 5/2 agar. Nitrate non-utilization (Nit)- mutants were developed for all A. flavus L strain isolates and tested for their genetic relatedness to the four Aflasafe KE01 strains. Levels of aflatoxin in maize grains were determined by enzyme-linked immunosorbent assay (ELISA) based Accuscan Pro-reader method. Aspergillus flavus L strain, A. flavus S strain and A. parasiticus were commonly isolated from the soil and maize grains while A. tamarii was only isolated from soil samples in in low proportions. A large proportion of A. flavus L strain isolates from soil (63.4%) and maize (90.2%) sampled from treated fields belonged to Aflasafe KE01 genetic groups implying displacement of aflatoxigenic fungi by the atoxigenic isolates in both soil and maize. In addition, Aflasafe KE01 strains survived between cropping seasons, implying that alternate season application of Aflasafe KE01 can be exploited. Application of Aflasafe KE01 resulted in up to 85% reduction in aflatoxin level. The study demonstrates the high efficacy of Aflasafe KE01 in aflatoxin reduction in hot spot areas of varying agro-climates.