Diversity and distribution of soil nematodes in Ngere tea catchment area of Murang’a county, Kenya

Abstract

A survey was conducted to determine the diversity and distribution of soil nematodes associated with tea in Ngere tea catchment area in Kenya. Soil samples were collected from six electoral zones of Ngere factory in Gatanga division Thika district, Murang’a County, Kenya. Nematodes were extracted and recovered from soil samples using a modified Baermann funnel method and identified under a light microscope based on their morphological characters. They were also classified according to their feeding habits. Ten genera belonging to, bacteriovores, fungivores, and omnivores were identified. Fungal feeding and parasitic nematodes were the most widely distributed trophic groups across the tea catchment area. Plant-parasitic nematodes recovered included Pratylenchus spp., Helicotylenchus spp. , Rotylenchus spp.,Aphelenchus spp., Rotylenchulus spp., and Xiphinema spp .Tylenchus spp was the most frequently occurring species in the soil (60.47%) where the population was 429 followed by Pratylenchus spp with 55.81% frequency rating and a population of 404 while Aphelenchus spp had frequency rating of 48.84% and a population of 530. Ditylenchus and Rotylenchus spp had the lowest frequency rating of 6.98 and 4.65%, respectively, while Rotylenchus spp had the lowest population of 33. Six genera of plant parasitic nematodes were encountered in the collected soil samples. These plant parasitic nematodes were identified as Pratylenchus spp., Aphelenchus spp.,Helicotylenchus spp.,Tylenchus spp.,Xiphinema spp and Duotylenchus spp. Pratylenchus spp. and Tylenchus spp. were the most frequently occurring species in the soil (50%) with a population of 25 and 21, respectively, which was followed by Helicotylenchus spp.,Aphelenchus spp., Xiphinema spp., and Duotylenchus spp. with 16.67% frequency rating and a population of 10, 10, 3 and 20, respectively. Pratylenchus spp had the highest nematode population of 28.09% and the lowest nematode population was Xiphinema spp., having a population of 3.37%. The correlation between nematode population counts and total organic carbon content was not significant at P≥0.05.