Abstract

Common beans (Phaseolus vulgaris L.) are the most important legume staple food in Kenya coming second to maize. In Central Highlands of Kenya, the 0.4-0.5ton ha-1 output is below the genetic yield potential of 1.5-2ton ha-1 partly due pests and diseases. Plant parasitic nematodes (PPN) have been reported to cause yield losses of up to 60% on beans. Though bean production is important in the Central highlands of Kenya, information on PPN associated with the beans in the region is lacking. This study was therefore undertaken to establish the diversity of PPN associated with common beans and to assess the root knot nematode damage on beans in the region. The study covered 50 farms (32 in Kirinyaga and 18 in Embu Counties) distributed in eight localities namely Kibirigwi (L1), Makutano (L2), Kagio (L3), Mwea (L4) and Kutus (L5) in Kirinyaga County and Nembure (L6), Manyatta (L7) and Runyenjes (L8) in Embu County and covering three Agro Ecological Zones (AEZs); UM2 (L1, L2, L3 & L4), UM3 (L5, L7 & L8) and UM4 (L6) AEZs. Manyatta (L7) and Nembure (L6), had the highest and second highest gall indices, respectively, while Kibirigwi (L1), Makutano (L2) and Mwea (L4) had some of the lowest gall indices. The most common PPN in bean roots were Meloidogyne spp. Pratylenchus spp. and Scutellonema spp. with a frequency of 94.38%, 78.25% and 59.13%, respectively. This further confirm the importance of these nematodes in bean production systems. Upper Midland 3 (UM3) AEZs and UM4 had higher nematode population densities and diversity than UM2. Disease severity and nematode composition and distribution were notably low in the irrigated areas Kibirigwi, Kagio and Mwea compared to rain-fed areas such as Makutano, Nembure and Manyatta.

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