Abstract:
Contamination of maize by fungi represents significant health and economic problems
in developing countries as well as the developed world. Fungicides are used to control
plant fungal infections in fruits and vegetables but can be useful in controlling fungal
infestation of maize in the field. This study was carried out to determine the in vitro
efficacy of four fungicides on fungi isolated from mycotoxin contaminated maize from
different regions in Kenya. A total of 138 maize samples which were part of the study
KEMRI-SSC 2151 that tested positive for aflatoxin and fumonisins were subjected to
mycological analysis in this study. The samples were collected from Machakos,
Nairobi, Mombasa, Kitale and Kisumu. The fungicides Milraz, Antracol, Mistress and
Victory were prepared according to the manufacturer’s instructions and applied on
four maize kernels from each sample before direct plating on Sabourauds dextrose
agar (SDA). Untreated maize kernels from each sample were also inoculated on SDA
concurrently as controls. The plates were incubated at 30oC for 72 hours after which
fungal growth on the kernels was examined and scored in the range of 0 to 100%
infestation. Percentage germination of maize kernels on the culture plates was also
scored in the range of 0 to 100%. Fungi growing on the maize kernels were identified
using macroscopic and microscopic features. The activity of the test fungicides on
pure fungal isolates was determined by disk diffusion method. Twenty microlitres of
each diluted fungicide was impregnated on 6 mm disks and placed aseptically at the
centre of the culture in three replicates before incubation at 30oC for 72 hours. Zone of
inhibition on the disks was measured to the nearest millimeter. Pearson correlation
analysis was used to analyze the effect of the test fungicides on maize germination.
The mycotoxin positive maize samples were significantly infested by fungi of the
genera Aspergillus, Fusarium, and Penicillium. There was a significant difference
(p<0.05) in fungal infestation per region where Mombasa had the lowest infestation of
72.5% while those from Nairobi had the highest infestation of 99.1%. There was a
significant inhibition [p<0.05 (0.00)] of fungal growth on the treated maize kernels
compared to the untreated. Twenty six percent and 34% of mycotoxin contaminated
maize samples treated with Mistress and Victory fungicides respectively were not
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infested, while those treated with Milraz and Antracol were 10% and 14%respectively.
Thirty one isolates were found to be resistant to more than one of the test fungicides.
There was a significant positive correlation [(R2=0.054, p<0.05)] between germination
and fungicide treated maize kernels. This work has demonstrated the potential use of
the test fungicides for the control potentially toxigenic fungi affecting maize. The
study also underscores the diversity and existence of fungicide resistant fungi in
mycotoxin contaminated maize. Field experiments should be conducted to ascertain
the field efficacy of the four fungicides as well as the extent of resistance to other
fungicides that could impact the use of related antifungal drugs used clinical settings
for treatment of fungal infections.
