Five samples of 1 kg each of organic soil (10.14 dag/kg) were autoclaved at 120 °C for 1 hour, five were heated in a 660 watt and 2450 Hz microwave oven at full power for 4 min, and five were not heat-treated. Roots of Mucuna aterrima, Crotalaria juncea, Tagetes erecta and Lycopersicon esculentum were macerated, separately, in 1000 ml of tap water in a blender at low speed for 30 s, then sieved. Each of the resulting suspensions or just tap water (control treatment) was poured on one of the different soil samples inside a plastic bag and stored at 28 °C for 24 h. Seventy-eight bacterial isolates were obtained from the soil samples by serial dilution and selected for a subsequent assay for the biocontrol of Meloidogyne javanica. Tomato seeds were soaked in suspension of each bacterial isolate, then sowed in substrate inside plastic tubes in the greenhouse. The seedlings were each inoculated with 400 eggs of the nematode. The isolate UFV-6 of Escherichia coli reduced the number of galls to the highest extent (80%), and UFV-8 of Citrobacter freundii was the most effective in reducing number of eggs (83%). The identification of the isolates was done by fatty acid analyses and biochemical tests.
isolation; biological control; thermic treatment; root-knot nematode
