Identification of soil nematodes in Ngere tea catchment area of Murang’a County, Kenya

Abstract

xvii ABSTRACT Tea is one of the leading cash crops in Kenya and makes significant contribution to the economy. It is with this reason that intensive studies are needed to expand and sustain tea production. Nematodes are roundworms in the phylum nematoda; they are a very diverse group of organisms in the soil and are represented in most soil types. The extent of diversity of microorganisms in soil is seen to be critical to the maintenance of soil health and quality since nematodes play a critical role in decomposition of organic matter, nutrient cycling and also cause serious damage to crops. The objectives of this research were to characterize and identify groups of nematodes that are associated with soil in tea growing areas of Ngere. Nematodes were extracted and recovered from soil samples using a modified Baermann funnel method. The isolated nematodes were identified under a light microscope based on their morphological characters. DNA was extracted from the isolates and PCR-RFLP was performed. The amplified DNA fragments were sequenced and compared with sequences in databases. Eleven nematode genera belonging to bacterivores, fungivores, and plant feeding nematodes were identified. Fungal feeding and parasitic nematodes were the most widely distributed trophic groups across the tea catchment area. Nematodes recovered included Pratylenchus spp., Helicotylenchus spp., Rotylenchus spp., Aphelenchus spp., Longidorus spp., Ditylenchus spp., Cervidellus spp., Hoplolaimus spp., Xiphinema spp., Tylenchus spp., and Meloidogyne spp. The correlation of the nematode population and organic carbon content showed a significant positive correlation (R=0.246) at P<0.05. The study showed that there is diversity of soil nematodes inhabiting tea soils in Ngere tea catchment area. The effect of tea on the structuring of nematode communities should be studied and documented.