Incidence of Aflatoxigenic Fungi and Aflatoxins in Maize Cultivated in Highland and Mid-altitude Agro-ecological Zones in Kenya

Abstract

Kenya has had recurrent aflatoxicoses of regional epidemiological pattern spanning over three decades now. A comparative study was therefore undertaken aimed at establishing factors contributing to fungal and aflatoxin contamination differences in maize cultivated in two Agro-Ecological Zones. Methods: A total of 309 maize samples obtained from the Highland Agro-Ecological Zone and Mid-Altitude Agro-Ecological Zone of Kenya were analyzed in a three year study, 2008-2010. A purposeful sampling technique was used. Aflatoxigenic fungal contamination involved culture on modified Potato dextrose agar supplemented with Yeast Extract Sucrose agar and 0.3% β-cyclodextrin. Aflatoxin quantification was by a commercial Enzyme-Linked Immunosorbent Assay (ELISA) kit. The findings from these two variables were compared according to the agroecological zone. Similarly, correlation analysis between the grains’ moisture content, fungal and aflatoxin contamination was undertaken. Results: Significant differences existed both in the mean grains’ moisture content and mean fungal load for maize samples from the two Agroecological zones (P < 0.001) with 12.8% and 3.0 CFU/g, respectively for Highland samples while Mid-Altitude samples had 13.2% M.C. and 83.5 CFU/g, respectively. A significant agro-ecological relationship was established regarding frequency of aflatoxigenic fungal species, with Aspergillus flavus in only 8.4% of Highland samples but predominant in 54.3% of Mid-Altitude samples samples(X2=16.764, p=0.05). Significant regional differences (P< 0.001) also existed regarding aflatoxin contamination, occurring in only 18% of Highland samples at 2.0 μg/kg mean contamination level and 73.7% of Mid-altitude samples at 14.0 μg/kg mean aflatoxin level. However, weak correlation existed between fungal and aflatoxin contamination in both Agro-Ecological Zones. Use of certified maize seed was a common practice among farmers in Highland Agro-Ecological Zone. Conclusion: The observed regional differences in both the fungal and aflatoxin load could be attributed to agro-ecological conditions and farming practices. The cool humid agro-ecological conditions prevalent in the Highland Agro-Ecological Zone together with sound farming practices particularly use of certified maize seed could have accounted for the lower contamination levels. Serious research on development of maize varieties that are not only drought resistant but also high yielding and resistant against pathogenic fungal infections including aflatoxigenic fungi is urgently needed so as to encourage farmers in the Mid-altitude Agro-Ecological Zone to adopt modern maize cultivars over the indigenous types.