Antagonistic potential of Paenibacillus elgii HOA73 against the root-knot nematode, Meloidogyne incognita

This study was conducted to evaluate the nematicidal potential of Paenibacillus elgii strain HOA73 against the root-knot nematode, Meloidogyne incognita, under both in vitro and in vivo conditions. The novel strain HOA73 (GenBank accession number JQ12069) produced hydrolytic enzymes including gelatinase and chitinase. Exposure of M. incognita to various concentrations (10-30%) of the bacterial culture filtrate (BCF) or 0.05-0.4 mg ml(-1) of the crude enzymes produced by P. elgii HOA73 significantly reduced hatch of the second-stage juvenile (J2) and caused substantial mortality under in vitro conditions. The hatch inhibition and J2 mortality rate was enhanced with the increase in the concentration of BCF and the crude enzymes. Similarly, the antagonistic effects also increased significantly over the time for which the treatments were given. Moreover, the crude enzymes partially destroyed cuticle layers of eggs and juveniles at 0.4 mg ml(-1) concentration. Furthermore, the pot experiment indicated that addition of HOA73 culture into potted soil significantly reduced the root galling, number of egg masses and nematode population by 62.1%, 69.8% and 53.0%, respectively, as compared to the control at 7 weeks after M. incognita infestation. HOA73 inoculation also promoted tomato plant fresh shoot weight by 17.9% as compared to control. Hence, the present results demonstrated the ability of P. elgii HOA73 as a potential biocontrol candidate against the root-knot nematode as well as a plant growth promoter for tomato.