Nematicidal potential of plant growth-promoting rhizobacteria against Meloidogyne incognita infesting tomato under protected cultivation

Background: In the protected cultivation of tomato (Solanum lycopersicum L.) crop, the severity of root-knot nematode, Meloidogyne incognita, incidence is alarming nowadays. To combat this, growers usually prefer using synthetic chemical pesticides, which in turn results in harming non-target beneficial microbes present in the soil micro-flora and indirectly toxic to human health. Therefore, attempts were made to find out the nematicidal potential of plant growth-promoting rhizobacteria (PGPR) against M. incognita, which could be used as an alternative solution to manage M. incognita incidence under protected cultivation. Results: Nematicidal potential of three PGPR isolates and their consortium against M. incognita under laboratory, pots, and field experiments was studied. Juvenile mortality of 91.67% was recorded at 100% consortium, followed by 73.33-81.33% by individual isolates. Similarly, hatching inhibition of 84.26% was recorded at 100% PGPR consortium followed by 78.48-83.21% in individual isolates after 96 h. of incubation. In the pots' study, soil drenched with PGPR isolates consortium, followed by Bacillus subtilis DTBS 5, Pantoea agglomerans, and Bacillus amyloliquefaciens DSBA 11 recorded significant reductions in the nematode incidence. Whereas in the field study, PGPR isolates applied as soil drenching also significantly reduced nematode's incidence in consortium, followed by B. subtilis DTBS 5 and B. amyloliquefaciens DSBA 11-treated soil in both field experiments. On an average, the plant growth promotion and fruit yield were enhanced than untreated control and PGPR isolates applied as soil drenching gave a significant result than bare root dip treatment. Conclusions: PGPR isolates, B. amyloliquefaciens DSBA 11, B. subtilis DTBS 5, and P. agglomerans, were found to be effective against M. incognita. This finding can be incorporated into the nematode management strategy in tomato crop grown under protected cultivation. Further to enhance the biocontrol efficacy of these PGPR isolates, suitable formulations of either individual or consortium need to be done.