Soil application of Bacillus thuringiensis Berliner isolates against root-knot nematode (Meloidogyne javanica (Treub) Chitwood) in okra (Abelmoschus esculentus (L.) Moench)

Abbasi, M. W. and Khan, M. Q. and Zaki, M. J. and Shaukat, S. S. and Rauf, A. and Ahmed, N. and Azeem, M. and Tariq, M. (2019) Soil application of Bacillus thuringiensis Berliner isolates against root-knot nematode (Meloidogyne javanica (Treub) Chitwood) in okra (Abelmoschus esculentus (L.) Moench). Acta Phytopathologica et Entomologica Hungarica, 54 (2). pp. 173-186. ISSN 0238-1249

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Abstract

Bacillus thuringiensis (B.t) is well known for its biocontrol potential against a variety of insects. Nematicidal potential of ten B.t isolates was tested against root-knot nematodes (Meloidogyne javanica (Treub) Chitwood) in vitro, under greenhouse as well as in field conditions. Eggs and second stage juveniles (J2) were exposed to 5 and 25% concentrations of bacterial cell-free aqueous extracts up to 96 h. B.t isolates showed lesser degrees of nematicidal activity at 5% concentration. However, some B.t isolates (B.t-14, B.t-16 and B.t-64) greatly reduced egg hatching and increased J2. All B.t isolates revealed suppressed egg hatching and increased mortality of J2 at 25% concentration. Soil applications with most of the B.t isolates under greenhouse and field conditions significantly improved height and fresh weights of root-knot nematode parasitized okra (Abelmoschus esculentus (L.) Moench). Some isolates, including B.t-64 reduced the number of galls and egg masses. B.t-64 reduced gall formation up to 70% under greenhouse conditions. However, 29% of decrease was observed in field conditions. Similarly, B.t-64 treated plants showed a 56% decreased in eggs/egg mass in a field experiment. Population of root-knot nematodes in the rhizosphere was decreased up to 61% in the field experiment as compared to control.

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