Ear rot and fumonisin B1 levels in self selected maize varieties at different harvest intervals in Western Kenya
Alakonya, Amos E.
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This study was aimed at carrying out a social economic and biological investigation on ear rot fungi, fumonisins and how they can be managed in maize in Western Kenya. During the study a Participatory Rural Appraisal (PRA) on farmer perceptions and practices in relation to maize ear not revealed that maize is the major crop in the region. Rotten maize is used for brewing, livestock feed, mixed with clean maize and sold during times of scarcity to consumers for maize meal. Maize ear rot was ranked as the most important crop protection constraint. Stalk borers and weevils were the most important field and storage pests respectively. The awareness of the health hazards associated with consumption of contaminated maize was limited among farmers and even extension staff in the two divisions. Evaluation of soil amendments in management of root infection by Fusarium moniliforme was evaluated in the greenhouse and field using several amendments. Non-amended soil acted as the control. The results revealed that different soil organic amendments had significant effects on the pathogenecity of F. moniliforme and plant performance. Goat manure had significant suppressive effects on root infection when used singly, but the effects were less than those obtained from a mixture of goat/Fym. Efficacy of various amendments were rated starting from the most to the least effective as follows; goat/Fym, neem/Fym, cotton, Fym, cott/Fym, sun/Fym, neem and sunflower respectively. In general organic amendments reduced the survival and infection of maize plants by F. moniliforme compared to controls. Use of soil amendments did not eliminate FB1 occurrence in maize when used at planting. The ear rot on-farm trial carried out in Tongaren and Malava divisions gave a broader assessment of the varieties in terms of response to natural infection to ear rot fungi and the actual farmers' practice under which these varieties are grown. The varieties revealed significant difference in percentage rotten grain, ear rot severity, yield of clean and rotten maize between the harvest intervals and also between varieties. Between 4th and 12th harvesting intervals the highest percentage rot was 40% in variety H622 and KSTP' 94 at 12th week harvest interval in Tongaren and Malava divisions respectively. Mycological analysis revealed that Fusarium spp were the most dominant ear rot fungi with F. moniliforme being the most prevalent fungi. Other ear rot fungi isolated but in low numbers included Stenocarpella spp, Aspergillus spp and Penicillium spp. The natural occurance of FB1 was investigated in four maize varieties at different harvest intervals by direct competitive ELISA method. From the maize samples analysed FB1 was found in 97.22% samples at levels ranging from 32ng/g to >5000ng/g the average concentration in clean maize, rotten maize all the sample analysed was 255ng/g, 2432ng/g and 1344ng/g respectively. It was established that FB1 is not just restricted to the rotten maize but also clean maize and that there is widespread occurance of the mycotoxin in maize from the two division. AFB1 occurred only in 4 samples out of the 72 samples analysed and ranged between 2.3ng/g to 4.1ng/g. All samples except for one were clean maize samples. The Fusarium moniliforme isolates produced FB1 in the range of 69ng/g to >5000ng/g. The study concluded that FB1 levels are higher than recommended and efforts to regulate the mycotoxin should be put in place in Kenya given that maize movement in Kenya is not restricted. It is now evident that people in W. Kenyan are exposed to higher levels of FB1 and there is need for farmer education and research towards low FB1 levels given the June 2004 mycotoxicoses in Eastern and Central Kenya.
- MST-Zoological Sciences