Management of root-knot nematode in tomato using antagonistic bacteria Stenotrophomonas maltophilia strain w 2–7

Twelve isolates of indigenous bacteria were isolated from the rhizosphere of root-knot nematode infected pepper, cardamom, rice and vegetables grown in different parts of Kerala. Culture filtrates of all these twelve isolates showed toxic effect against Meloidogyne incognita juveniles in preliminary screening. Bioefficacy study of the most effective four isolates on egg hatching and juvenile mortality revealed that two isolates were very effective, with maximum egg hatch inhibition and juvenile mortality. Highest egg hatching (5.35 to 38.71 percent) was observed in lowest concentration of culture filtrate (25%), from three to eight days after treatment, while at highest concentration (100%) it was 0.20 to 20.66. The two potential isolates at lowest concentration (25%) recorded 70.50 to 72.50 per cent juvenile mortality at 72 hours after exposure, while at 100% concentration it was 91.00 to 94.00 per cent. Molecular and biochemical characterization revealed the identity of these isolates as Stenotrophomonas maltophilia strain W 2–7 and Bacillus thuringiensis strain a57. Results of the pot culture study revealed that S. maltophilia strain W 2–7 (1x10⁷ cfu mL⁻¹) soil drenching @50 mL pot⁻¹ significantly reduced nematode population in soil (72.69 per cent) and root (82.23 per cent) and improved the growth parameters and yield in tomato. Result of the present study highlighted the biocontrol potential of S.maltophilia strain W 2–7 against M.incognita.