Prediction of root-knot nematode infestation using soil Characteristics in tomato fields in Mwea, Kirinyaga County, Kenya
Wendot, Kibet Philip
MetadataShow full item record
Tomato (Solanum lycopersicum L.) is a high value horticultural crop in Kenya. utritionally, the crop is rich in niacin, carotene, thiamine, and vitamin C. Mwea in Kirinyaga County is one of the major areas in Kenya where tomato is grown by smallholder farmers and is an important source of income. Tomato production in Kenya is hindered by losses due to diseases caused by pathogens that include plant parasitic nematodes. Among the plant parasitic nematodes, the root-knot nematode is the most predominant in Mwea. This study aimed at investigating the soil parameters that influence the distribution of the root-knot nematodes and map their distribution. This is important since it ensures that nematicide application is only to specific sites where these nematodes are found thereby saving on input costs as well as protecting the environment. The study consisted of surveys conducted in geo-referenced tomato production fields in seven tomato production sites in Tebere, Mwea. Soil sampling was done in a stratified random manner in both rainfed and irrigated tomato production fields in both dry and rainy seasons for determination of the spatial and temporal distribution of nematodes, respectively. Nematode extraction was done using the centrifugal floatation technique and identification done to genera level using morphological features. Soil parameters measured included soil pH, electrical conductivity, elevation and soil texture. Soil texture was determined using the hydrometer method. Detrended canonical correspondence analysis was performed to interpret and summarize major patterns of variation within the soil variable data and to estimate the ability of each soil variable to reflect variance in the entire plant parasitic nematode data set. The plant parasitic nematode incidence and diversity was determined using the Shannon-Weiner species diversity index. Fourteen genera of nematodes were identified with diversity indices ranging between 0.6 and 1.2. Rootknot nematode distribution differed significantly among different sites. Among the soil samples analyzed, 81% were positive for root-knot nematode infestation. There was no significant difference ,- between nematode densities in the dry and rainy seasons. Rainfed fields exhibited significantly higher root-knot nematode population densities compared to irrigated fields. The study established a great variability in the soil parameters in the area. The root-knot nematode distribution pattern, density and abundance were inversely correlated with the soil pH and positively correlated with soil electrical conductivity. Based on the inverse relationship between soil pH and root-knot nematode distribution in the Mwea ecosystem, maps of nematode distribution and soil pH were developed. This enables the possibility of designing a site specific system for management of root-knot nematodes. It is recommended that farmers should avoid uniform application of nematic ides in their production fields.