Effect of root knot nematodes on the growth of indigenous leafy vegetables in Kenya
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African indigenous leafy vegetables play an important role as income and food security crops in many rural and urban households in Kenya. However, root knot nematodes (RKN) constrain the production causing yield losses of 80 to 100 % on some of the vegetables depending on susceptibility and levels of inocula in the soil. The objective of this study was to investigate the effect of root knot nematodes on the growth of popular indigenous leafy vegetables. A green house experiment was conducted twice, where six indigenous leafy vegetables namely spider plant (Cleome gynandra), amaranth (Amaranth hybridus), black night shade (Solanum nigrum), cowpea (Vigna unguiculata), jute mallow (Corchorus spp) and sun hemp (Crotalaria juncea) were tested. The vegetables were planted in pots with sterilized soils. Half of the pots were infested with 2000 second stage juveniles of root knot nematodes. During growth, plant height data was taken every fortnight and on termination at 60 days after planting, data on galling index, egg mass index and the second stage juvenile counts was recorded. Root galling was estimated on a scale of 1-10, where 1 = resistant and 10 = most susceptible. The egg mass index was estimated on a scale of 1-5 and the juveniles count made from the roots. Galling index (GI), egg mass index and the juvenile (J2) counts differed significantly (p<0.05) among the vegetables tested. Amaranth had the least GI (1.7) and egg mass index (1.0) while black night shade had the highest GI (7.0), egg mass index (3.7) and the highest counts of juveniles. Spider plant, sun hemp and amaranth were rated as resistant while jute mallow, cow pea and black night shade were rated as susceptible. The identified resistant varieties can be used as rotation crops in agricultural production systems as a component of root knot nematode suppression in the soil.