Molecular characterization and non-chemical management of root-knot nematodes (meloidogyne spp.) on African nightshades in selected parts of Kenya
Nchore, Shem Bonuke
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Root-knot nematodes (RKN) (Meloidogyne spp.) cause up to 80 % yield losses in infected vegetables. A study was carried out to; assess the influence of farmers’ knowledge and awareness on RKN damage on African nightshades (AFNS); assess the incidence and severity of RKN on AFNS; characterize the RKN species infecting AFNS; screen the AFNS for response to RKN and determine the efficacy of solarizing soils amended with selected organic materials against RKN. A root-knot nematode survey was carried out in selected farms in Lower midlands 1 (LM1), Upper midlands 1 (UM1), UM2, UM3 and UM4 located in Nandi, Bungoma, Kakamega and Uasin Gishu Counties during the April to July 2014 growing season. The survey revealed that 53.6 % of the AFNS farmers were not aware of RKN. Majority (66.7 %) of the farmers planted AFNS using organic manure while 33.3 % used inorganic fertilizers. Farmers controlled RKN through the use of pesticides, crop rotation, woodash and uprooting diseased crops. Two hundred and fifty soil and root samples were taken from depths of 20 cm from ten different points per farm to determine the disease incidence and severity. Incidence and severity of 94.13 % and 2.63 respectively was reported. Galling index ranging from 1.3 to 4.43 was reported. Molecular characterization identified M. incognita, M. arenaria, M. hapla, M. javanica and M. lopezi from the surveyed areas. The response of AFNS to RKN varied from resistant to susceptible. Solanum eldoretiunum and S. scabrum were resistant, while S. sarrarachoides was tolerant in the greenhouse and field conditions. Solanum americanum and S. nigrum line IP03 were resistant in the greenhouse, but were tolerant to RKN in both field experiments, while S. nigrum landrace from Kakamega and S. opacum were resistant in the greenhouse and field test at Kenyatta University but were tolerant to RKN at Chepterwai. Both S. nigrum from Simlaw Seed Company and S. villosum line BG03 were susceptible in the field test at Chepterwai though they were tolerant in the field test at Kenyatta University. In addition, resistant and tolerant AFNS had lower RKN damage and reproduction compared to susceptible AFNS. Solarized soils amended with Cattle manure (Cm), Tithonia diversifolia (Td) and pymarc (Pm) reduced RKN population and damage significantly compared with non-solarized and non-amended controls. Solarization improved efficacy of Cm, Td and Pm against RKN reproduction and damage on S. villosum. Reproduction was lower on Cm, Pm and Td amended soils while galling index ranged from 0.7 to 2.2 in solarized soils compared to 1.4 – 5.0 in non-solarized soils. Sensitization of farmers on RKN damage and application of organic amendments to reduce disease incidence and severity is proposed. The dominant RKN identified threatens AFNS production in the surveyed regions. Farmers should grow tolerant AFNS on heavily infested soils to reduce RKN population and reproduction. The tolerant AFNS could also be used in breeding programs for the management of RKN. Solarizing soils amended with organic materials is an ideal integrated pest management strategy for combating RKN infecting AFNS.