Distribution and Diversity of Indigenous Trichoderma species in Machakos County, Kenya

Aim: This study was undertaken in order to determine the effect of land-use intensification on occurrence, distribution, and diversity of Trichoderma fungus.

Study Design: Cross-sectional study.

Place and Distribution of Study: Mycology Laboratory, University of Nairobi between March and September, 2014.

Methodology: Soil samples were collected from both Mwala and Kauti irrigation blocks in Kabaa irrigation scheme of Machakos County, in Kenya under three land use types (LUTs): intensively cultivated farmlands under irrigation, rainfed intensively cultivated farmlands and undisturbed lands. A total of 100 soil samples were obtained from the top 0- 20 cm depth. Trichoderma species were isolated using the dilution plate technique using Trichoderma-selective media (TSM).

Results: A total of 369 Trichoderma isolates were recovered from the three LUTs. These were identified and classified into eleven species. The species identified were: T. harzianum, T. koningii, T. viride, T. asperellum, T. atroviride, T. spirale, T. virens, T. tomentosum, T. brevicompactum, T. crassum and T. hamatum. The most abundant Trichoderma species was T. harzianum with a frequency of isolation of 38.87%, followed by T. koningii and T. viride at 18.03 and 15.49%, respectively. Trichoderma hamatum had the least isolation frequency at 0.41%. T. harzianum also had the widest distribution. The difference in abundance of Trichoderma in the three LUTs was significant (P=0.05). The undisturbed lands had a higher abundance of Trichoderma compared to the disturbed areas. Mwala irrigation block A had the least abundance while block D which is more recent in cultivation had highest mean abundance of Trichoderma. Difference in Trichoderma species mean richness between LUTs was not significant (P=0.203). Undisturbed lands had the highest richness. Undisturbed lands also had the highest diversity while irrigated lands were the least diverse

Conclusion: Enhanced land-use intensification lowers the abundance and diversity of Trichoderma in the soil.