Fungal and aflatoxin contamination in maize from Eastern Kenya and evaluation of possible management strategies

Abstract

Survey on fungal and aflatoxin contamination and evaluation of possible management strategies was carried after 2006/07 cropping season in nine agro ecological zones of greater Machakos district (Kangundo, Machakos and Yatta districts). The overall objective of the study was to assess fungal and aflatoxin contamination in maize in the greater Machakos district and evaluate possible management strategies to mitigate the aflatoxin problem. Questionnaires were used to gather information on production, storage, handling, and consumption practices. Samples of whole maize, semi-processed grains, posho mill sweepings, soils from farms and from under the maize stores were collected. Fungi from whole maize and semi-processed grains were isolated by direct plating, while for posho mill sweepings and soil by pour method and the fungi identified to species level. Aflatoxin contamination was determined using ELISA method. Field experiments were conducted to evaluate susceptibility of selected varieties to fungal and anatoxin accumulation. The varieties were inoculated with Aspergillus flavus isolated during the survey. Aspergillus rot was evaluated by visual ear rot rating scale. Most (88.0%) farmers planted their own selected local maize, some did not practice rotation, most (54.0%) harvested maize without husk, dried maize in cob form (94.4%) and on mats or polythene (56.7%). Most farmers stored shelled maize in houses in polypropylene bags (93.3%). Most traders sourced maize from local farmers (97.6 %) and commonly transported the maize by oxen pulled carts (49.8 %). The major fungal genera isolated [rom the samples were Fusarium, Aspergillus and Penicillium. The most frequently isolated Aspergillus species were A. flavus. and A. niger. Aspergillus jlavus and anatoxin levels in maize grains from farmers were found to be significantly different across agro-ecological zones. Semi-processed grains had the aflatoxin level of 5.1 ug/kg while posho mill sweeping had a level of 18.3 ug/kg. There was significant di fference among the maize varieties 111 Aspergillus rot rating during the long rains. Aspergillus flavus was re-isolated from cobs inoculated with A. flavus during long rains (19.0%) and short rains (9.9%). There was no significant difference among the varieties in Aspergillus rot rating and re-isolation of Aspergillus jlavus during short rains. Aspergillus jlavus was re-isolated from the inoculated maize samples. Varieties were not significantly different in anatoxin content. The results showed that anatoxin contamination of maize and maize products could be as a result of interaction of production, harvesting, storage, handling practices and presence of A. jlavus in soil, residues from previous crop and grain left over under store. All the varieties tested were susceptible to aflatoxin contamination. Training farmers on good agricultural practices, further work on susceptibility of a broad range of maize varieties grown in Kenya under diverse environments would be required. Continuous anatoxin surveillance in anatoxin hotspot areas is necessary. In addition, more research on Fusarium mycotoxins in maize would be necessary.