P. M. Wachira

Effects of Medicinal Plant Extracts and Photosensitization on Aflatoxin Producing Aspergillus flavus (Raper and Fennell)

This study was undertaken with an aim of exploring the effectiveness of medicinal plant extracts in the control of aflatoxin production. Antifungal properties, photosensitization, and phytochemical composition of aqueous and organic extracts of fruits from Solanum aculeastrum, bark from Syzygium cordatum, and leaves from Prunus africana, Ocimum lamiifolium, Lippia kituiensis, and Spinacia oleracea were tested. Spores from four-day-old cultures of previously identified toxigenic fungi, UONV017 and UONV003, were used. Disc diffusion and broth dilution methods were used to test the antifungal activity. The spores were suspended in 2 ml of each extract separately and treated with visible light (420 nm) for varying periods. Organic extracts displayed species and concentration dependent antifungal activity. Solanum aculeastrum had the highest zones of inhibition diameters in both strains: UONV017 (mean = 18.50 ± 0.71 mm) and UONV003 (mean = 11.92 ± 0.94 mm) at 600 mg/ml. Aqueous extracts had no antifungal activity because all diameters were below 8 mm. Solanum aculeastrum had the lowest minimum inhibitory concentration at 25 mg/ml against A. flavus UONV017. All the plant extracts in combination with light reduced the viability of fungal conidia compared with the controls without light, without extracts, and without both extracts and light. Six bioactive compounds were analyzed in the plant extracts. Medicinal plant extracts in this study can control conidia viability and hence with further development can control toxigenic fungal spread.

Conservation and Sustainable Management of Soil Biodiversity for Agricultural Productivity

Soil biodiversity represents the variety of life belowground whose interaction with plants and small animals forms a web of biological activity. It improves the entry and storage of water, resistance to soil erosion, and plant nutrition, while also controlling soil pests and disease, and facilitating recycling of organic matter in the soil. Soil biodiversity is therefore the driver of healthy soil for sustainable crop production.

Chapter 5:Agrobiodiversity and Potential Use for Enhancing Soil Health in Tropical Soils of Africa

a Department of Land Resource Management and Agricultural Technology, University of Nairobi, P.O Box 29053-00625, Nairobi, Kenya; b Department of Agricultural Economics, University of Nairobi, P.O Box 30197-00100, Nairobi, Kenya; c School of Biological Sciences, University of Nairobi, P.O Box 30197-00100, Nairobi, Kenya; d Department of Plant Sciences, University of Nairobi, P.O Box 30197-00100, Nairobi, Kenya; e World Agroforestry Centre, P.O Box 30677, Nairobi, Kenya*Corresponding author *E-mail: fredrick.ayuke@yahoo.com

Co-occurrence and Diversity of Soil Trichoderma and Fusarium species from Different Land Use Intensities in Machakos County, Kenya

Soil fungi are important components of the soil biota and their diversity is a good indicator of soil health. Soil fungi respond differently to land use practices and to their relative populations. The cooccurrence and diversity of Trichoderma and Fusarium species against various land use types (LUTs) was investigated. The genus Trichoderma contains many important species with potential for biocontrol of soil-borne plant pathogens as well as high saprophytic capacity while the genus Fusarium has many species that are highly pathogenic to plants and with potential for mycotoxin production. This research adopted a cross-sectional study design. Soil samples were collected from 3 land-use types (LUTs) in Kabaa irrigation scheme in Machakos County, Kenya, that is, intensive land-uses under irrigation and rain-fed agriculture and undisturbed lands. From the top soil layer, 100 soil samples were collected. The samples were processed and 369 Trichoderma Original Research Article Maina et al.; ACRI, 4(1): 1-13, 2016; Article no. ACRI.24894 2 and 1,546 Fusarium isolates recovered. Fusarium had a higher abundance than Trichoderma in the highly disturbed lands. In the undisturbed lands, Trichoderma had a higher abundance than Fusarium. There was a clear negative correlation between Trichoderma and Fusarium occurrence and diversity. The study further revealed that disturbance had a positive effect on Fusarium but a negative one on Trichoderma.