A study on the occurrence, diversity and distribution of FUSARIUM spp. in the Arable soils in Zambia

Fusarium species are ubiquitous soil inhabiting fungi. They have the ability to exist as saprophytes degrading lignin and complex carbohydrates associated with plant debris. Although the predominant role of these saprophytes is harmless, many species are pathogenic to plants, especially in agricultural settings.The occurrence, distribution, richness and diversity of Fusarium species were determined from selected arable soils around Lusaka District. The experimental soils were collected from 12 commercial farms of the Lusaka District situated in four sitesviz Lusaka North, East, South and West. One hundred and five (105) isolates of Fusarium species were obtained and plated on a Selective Fusarium Agar medium following the conventional soil dilution plating method. The general objective of the study was to determine the occurrence, diversity, richness and distribution of Fusarium spp. in arable soils of the District. The specific objectives of the study were to: i) evaluate the occurrence of Fusarium spp. ii) determine their species diversity and iii) establish their distributionin the study area.A total of eight species of Fusarium were identified on the basis of colony morphological characteristics; number and type of phialids; and shape, size and type of conidia.This study showed that Fusarium oxysporum(47.6%) and F. solani(30.5%) were the most dominant species with regard to the frequency of occurrence. The other six Fusarium species showed much reduced occurrence and ranged between 1.9% and 5.7%.There were significant differences(p=0.05) in their occurrenceof among farms. There were also significant interactions between farms and sites with regard to species diversity and richness.The soils differed in physical and chemical properties. The study has also demonstrated a clumped distribution of Fusarium spp. as shown by the variance/mean ratio analyses in the 8 of the 12 sampled farms. The study provides the baseline information on the occurrence, diversity and distribution of Fusarium spp. in certain agricultural soils of Zambia. These findings suggest that farmers should avoid cultivating Fusarium-susceptible crops in such soils.