Susceptibility of mycotoxigenic fungi to commercial fungicides, a potential tool for mycotoxin control in maize in Kenya

Abstract

Mycotoxin contamination of food grains represents significant health and economic challenges in developing countries as well as the developed world. Mycotoxin- producing fungal species affecting maize mainly belong to the genera Aspergillus, Fusarium, and Penicillium.They pose serious phytopathological and mycotoxicological risks both at pre-harvest and post-harvest stages. Maize in Kenya has been associated with frequent outbreaks of aflatoxin contamination. A number of mycotoxin control strategies both chemical and biological have been developed as potential tools for mycotoxin control. A Laboratory based cross-sectional study was carried out in a Mycology Laboratory at the Center for Microbiology Research in Kenya Medical Research Institute, Nairobi, Kenya. A total of 138 maize samples obtained from Machakos, Nairobi, Mombasa, Kitale and Kisumu were subjected to mycological analysis. The samples were treated with the fungicides; Antracol (propineb), Milraz (propineb700g/kg and Cymoxanil60g/kg), Mistress (Cymoxanil 8% and Mancozeb 64%) and Victory (Metalaxy 80g/kg and Mancozeb 640g/kg.) before inoculation on Sabourauds dextrose agar (SDA). Infestation rates on fungicide- treated and non treated control maize kernels were scored. The susceptibility of the isolates to the four test fungicides was determined by disk diffusion technique. All the maize samples were infested by moulds and there was a significant difference in regional infestation rates (p<0.05). Maize from Mombasa had the lowest infestation of 72.5% while Nairobi was the highest with 99.1%. Fungi of the genera Aspergillus, Fusarium, and Penicillium were frequently isolated from the five regions. There was a significant reduction {p<0.05 (0.00)} of infestation rates on fungicide- treated maize compared to the untreated. Generally, 26% (n=35) and 34% (n=47) of maize samples treated with Mistress and Victory, respectively had 0% infestation while those treated with Milraz and Antracol were 10% (n=14) and 14% (n=19), respectively. Some mycotoxigenic isolates were found to be resistant to more than one of the test fungicides. However, their in- vitro antifungal activity is of great importance and could further be evaluated to determine their field efficacy for mycotoxin control in maize.

Key words: Maize, Mycotoxigenic fungi, Fungicides, Susceptibility.