A taxonomic survey of post-harvest fungi on horticultural crops in Kenya
Ondijo, David Ojwang'
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A floristic survey of post-harvest crop fungi on some widely used horticultural crops namely, Musa paradisiaca Linn., Lycopersicon esculentum Miller, Persea americana Bras. and Ananas comosus Merril, was carried out. Rotting fruit samples were incubated in a moist chamber and mycelium of individual fungus species transferred onto PDA plates and incubated for 3-7 days at a temperature of 26°C to allow soporulation. Pure cultures were then obtained by single spore isolation. The fungi were observed under a microscope at a magnification of x100 and x400 and diagnostic characters were recorded and illustrated. From the characters of pure culture and microscopic observation, the fungi were identified using key and literature with illustrations on fungi such as CMI description of pathogenic fungi and bacteria. A total of 26 fungi species were isolated and identified. Incidence of occurrence of fungi on each of the crops in a season and in different seasons was investigated by scoring their frequencies on the study samples. Different frequencies of fungi on same crop was noted. Similarly a higher incidence of occurrence during the wet season as compared to the dry season was observed. In relation to the four study crops, some of the 26 fungi species exhibited host specificity while others were observed to be general pathogens. Pathogenicity studies were conducted to establish the parasitic states of fungi isolated in relation to fruits isolated from. Inocula were prepared from pure cultures and healthy, unblemished fruit samples subjected to various categories of tests. ANOVA test of the resulting data showed significant differences between treatment means of 24 out of the 26 fungi isolated (P > 0.5). Further comparison of the treatment means using LSD technique, indicated that some of the fungi could attack unblemished fruits. Similarly some species were thought to attack fruits long before harvest. The study gave a preliminary list of post-harvest crop fungi associated with the four crops investigated, their possible mode and time of infection and host specificity, together with a reference collection in form of herbarium specimens, information that is vital for effective control of the pathogens.