Fungal Pathogens Affecting Terminalia Brownii Flowers, Fruits andSeeds in Drylands, Kenya

Abstract

Terminalia brownii Freshen (Combretaceae family) is a multipurpose agroforestry tree species widely grown in Eastern Africa’s dry lowlands. However, it needs to be more utilised, which has led to concern about its regeneration, which is hindered by low seed germination percentages. The study was carried out in three sites representing distinct ecological regions in agrosilvopastoral agroforestry systems where T. brownii trees are naturally distributed in the drylands of Kenya. These sites are Nduumoni, Kimose and Kendu Bay, in Kitui, Baringo and Homa Bay counties. Farmers practice subsistence crop farming mixed with livestock and T. brownii trees within the same farming system. The study investigated incidences of fungal disease infection in flowers and fruits during their growth. Flower buds, flowers, and immature and mature fruits were sampled for culturing from 30 reproductively mature trees selected randomly within 5.0 ha in an agrosilvopastoral agroforestry system in each site. Samples of 100 flower buds, flowers, and immature and mature fruits were surface sterilised using 40 % hydrogen peroxide for 2 minutes and rinsed in distilled water. These were plated on Malt Extract Agar (MEA) media and incubated at 28 ± 20C for seven days; fungal colonies were evaluated and subcultured to obtain pure cultures, and pathogens were identified using morphological characteristics. Statistical analyses were done using the Kruskal-Wallis and Bonferroni multiple comparison tests to determine the differences
among the sites. Common fungal pathogens isolated were Fusarium spp (42-49%), Alternaria spp (29-33%), Bostryosphaeria spp (4-12%), Cladosporium spp (38%) and Pestalotia spp (7%). There were significant differences (p<0.05) in fungal infection between flower buds, flowers, immature, mature fruits and extracted seeds but not across sites. Flower buds had minor fungal diseases, thus indicating that infection took place during and after flowering. The author hypothesises that these fungi could affect seed germination by either causing seed deterioration or affecting the germinants, lowering seed quality.