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" The distribution, toxigenicity, and evaluation of Fusarium species on millet and sorghum seed from Nigeria, Lesotho, and Zimbabwe "
N. B. N. Onyike
P. E. Nelson
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Latin Dissertation
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English
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| Record Number
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1112678
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TLpq303717605
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| Main Entry
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N. B. N. Onyike
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P. E. Nelson
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| Title & Author
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The distribution, toxigenicity, and evaluation of Fusarium species on millet and sorghum seed from Nigeria, Lesotho, and Zimbabwe\ N. B. N. OnyikeP. E. Nelson
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| College
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The Pennsylvania State University
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| Date
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1989
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| student score
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1989
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| Degree
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Ph.D.
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| Page No
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126
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| Abstract
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Fusarium species, which cause a variety of diseases on a wide range of agricultural crops, cause deterioration of cereal grains after harvest, and produce mycotoxins on cereal grains and other products, have been obtained from sorghum and millet grain used for human and animal food in Nigeria, Lesotho and Zimbabwe. Fusarium species were isolated from millet and sorghum grain and from soil in which these crops were grown, on a modified pentachloronitrobenzene selective medium for Fusarium. The Fusarium cultures growing from the seeds, plant debris or soil particles were transferred individually to carnation leaf agar, potato dextrose agar, potassium chloride agar, and soil agar. These cultures were grown at 23C under a mixture of cool white and black fluorescent lights on a 12-hr photoperiod for 10 days and identified. A randomly selected sample of Fusarium moniliforme and F. nygamai cultures were tested for toxigenicity with the duckling bioassay and evaluated by isozyme analysis. The most prevalent Fusarium species recovered from millet seed were F. equiseti (34.3%), F. nygamai (25.5%), F. moniliforme (23.6%) and F. semitectum (10.4%). On sorghum, the most prevalent species were F. moniliforme (64.5%), F. nygamai (7.5%), and F. equiseti (6.8%), while F. oxysporum (37%), F. equiseti (30%) and F. solani (13.5%) were the most prevalent species in soil. Other Fusarium species found associated with millet and sorghum grain included F. chlamydosporum, F. graminearum, F. sporotrichioides and F. compactum. The same Fusarium species were recovered from millet and sorghum seeds and from the soil. The cultures recovered showed variation in colony morphology, pigmentation, size and shape of macroconidia, and the length of microconidial chains, when present. Fusarium nygamai cultures were in two distinct morphological groups, with one group producing long chains of microconidia and the second group producing short chains of microconidia. Toxigenicity tests on randomly selected cultures of F. moniliforme and F. nygamai showed 70% of F. moniliforme and 91% of F. nygamai to be highly toxigenic; toxigenicity was not related to host or to the location of the crop. Isozyme patterns showed a close relationship between F. moniliforme and F. nygamai which corresponded to the morphological resemblance observed between the two species. Morphological differences between the two groups of F. nygamai, distinguished by the length of the microconidial chains, were not correlated with isozyme patterns or with toxigenicity.
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Agronomy
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Biological sciences
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Botany
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Microbiology
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Plant pathology
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Plant pathology
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