Incidence of Aflatoxigenic Fungi and Aflatoxins in Maize Cultivated Under Rain-Fed and Irrigation Farming Systems in Kenya

Abstract

Aims: This study was undertaken with the aim of establishing whether irrigation reduces aflatoxigenic fungal and aflatoxin contamination of maize samples purposefully selected from two regions practicing rain-fed and irrigation farming systems Kenya. Place and Duration of Study: Rain-fed maize samples were obtained from Kitui and Kibwezi districts while irrigation samples were from Perkerra Irrigation scheme in Baringo County. Moisture content and fungal contamination analysis was undertaken at the Centre for Biotechnology and Bioinformatics, University of Nairobi during 2008-2010 periods. Analysis for aflatoxin contamination was done at BORA Biotech Ltd laboratories, Nairobi. Methods: A total of 155 maize samples were obtained from two regions practicing Rain Fed Farming System and Irrigation Farming System. A purposeful sampling technique was used during the two year study. Aflatoxigenic fungal contamination involved culture on modified Potato dextrose agar supplemented with Yeast Extract Sucrose Agar containing 0.3% β-cyclodextrin. Aflatoxin quantification was done by Enzyme-Linked Immunosorbent Assay (ELISA). The findings from these two variables were compared according to the farming system. Correlation analysis between the grains moisture content, fungal and aflatoxin contamination was undertaken. Results: Significant difference existed in the mean grains’ moisture content (M.C.) of maize samples from the two farming systems (P < 0.001).The mean moisture content was 13.2% and 12.5% for Rain Fed and Irrigation Farming System samples, respectively. A significant relationship was established in the variation and frequency of aflatoxigenic fungal species. Aspergillus flavus occurred predominantly in Rain Fed samples (X2=16.764, p=0.05). The proportion of samples with both fungal and aflatoxin contamination was comparatively higher among Rain Fed than Irrigation samples with aflatoxin contamination in 73.7%, and 59%, of the samples, respectively. However, difference in the mean fungal and aflatoxin contamination according to farming system was insignificant. A positively weak correlation existed between the total fungal load and aflatoxin levels in maize samples from both farming systems (R2=0.041 and R2= 0.004, respectively). Conclusion: Use of irrigation, certified maize seed varieties, adequate maize grain drying and sound farming practices contribute to lower fungal and aflatoxin contamination. Findings from this study are of great significance in creating awareness on the need to modify the pre-harvest and post-harvest farming practices in the various irrigations schemes that the Kenyan government continues investing billions of money in revamping. These practices will ensure that the maize harvests do not go into waste due to fungal and aflatoxin contamination thereby contributing to creation of national food safety and security.