The characterization of chitinolytic soil bacterial isolates for their antagonistic activity against root knot nematode Meloidogyne incognita: an effort towards developing ‘green’ nematicidal agents

Root knot nematode ( Meloidogyne spp.) is one of the most infective nematode genera having a wide range of host plants. The study was aimed to isolate chitinolytic soil bacteria, characterize their properties, and to determine their antagonism against root knot nematodes. Out of the ninety-five bacterial isolates, twenty-five Gram-positive and non-hemolytic isolates were screened based on the production of extracellular enzymes, biofilm formation, antifungal activity, and in vitro antagonism against root knot nematodes. Ten isolates exhibited statistically significant antagonism in terms of percent mortality of the second-stage juvenile (J2) and percent egg hatch inhibition compared to untreated sets. In the polyhouse trial, these ten isolates applied at 1.0 billion cfu per growbag planted with cucumber seedlings reduced the egg masses to 69%, number of females to 64%, and final nematode populations to 68%. Subsequently, vegetative growth parameters such as shoot height, shoot weight, and root weight increased, compared to the untreated control treatment, in plants grown for forty-five days in soil infected with nematodes. Nine among the ten isolates were identified as Bacillus spp. (99–100% similarity), and one isolate was identified as Paenibacillus sp. (95% similarity) using whole-genome sequencing. Overall, the present study suggested that the chitinolytic bacterial strains showing biofilm formation, enzyme production, and antifungal activity demonstrate an important trait to exhibit antagonism against root knot nematodes.