Abstract

Land-use intensification has a significant influence on occurrence of soil microorganisms. The effect of this phenomenon on Fusarium species is poorly characterized. One hundred soil samples were obtained from 3 replicated land- use types (LUT) in Mwala and Kauti irrigation regions in Machakos County. These included two intensive land-uses under irrigation and rain-fed agriculture and undisturbed lands. Mwala irrigated lands were divided into four blocks based on history of cultivation. Using soil dilution plate technique, 1,546 isolates of Fusarium were recovered and identified into twelve species namely; F. oxysporum, F. solani, F. nygamai, F. equiseti, F. chlamydosporum, F. beomiforme, F. verticillioides, F. proliferatum, F. acuminatum, F. compactum, F. semitectum, and F. merismoides. Fusarium oxysporum was the most abundant and diverse Fusarium species. Fusarium semitectum, F. compactum and F .merismoides had the least distribution being isolated from only one LUT. Fusarium beomiforme and F. acuminatum were recovered from irrigated farmlands only while F. verticillioides, F. proliferatum and F. acuminatum were restricted to disturbed lands only. The difference in abundance of Fusarium between the three LUTs was significant (P = 0.047) with irrigated lands having the highest abundance. Mwala block A had the highest abundance, richness and diversity of Fusarium. Lands with a higher intensity of disturbance had a higher abundance and richness of Fusarium than the less undisturbed lands. This may have severe implication on crop production as most species of Fusarium isolated are pathogenic. Sustainable ways of controlling these potential crop pathogens should be sought.

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