Influence of Soil Types on Citrus Nematode Species Diversity and Abundance Under Varied Ecological Conditions in Kenya

Abstract

Plant-parasitic nematodes (PPNs) cause major crop losses by damaging plant roots and causing reduced absorption of soil nutrient elements. A two-year survey in 2018 and 2019 was conducted in most citrus growing regions in Kenya to assess the abundance, distribution and diversity of plant parasitic nematodes from different soil rhizosphere. Nematode population in 200cc of soil and 5g of roots were collected for PPNs extraction by using modified Baermann’s technique and identification by morphological features. The findings indicated that four major genera were abundant in different citrus growing ecological zones in Kenya. The identified species were Meloidogyne incognita, Tylenchulus semipenetrans, Helicotylenchus dihystera and, Pratylenchus brachyurus. The most abundant species in all the surveyed localities was T. semipenetrans. Factor regression analysis results showed that modest rainfall amounts favoured high density populations of PPNs on citrus roots where soil types of Rackers in Baringo and Luvisols, Ferralsols and Cambisols in Machakos County were dominant. Tylenchulus, Meloidogyne and Helicotylenchus species were most abundant in Kitale, Taita-Taveta, Kilifi and Kwale. The results presented here show how possible population density of PPNs in varied soil class types, rainfall amounts and prevailing temperature would be influenced by abiotic factors therein.