The characterization of chitinolytic soil bacterial isolates for their antagonistic activity against root-knot nematode Meloidogyne incognita: An effort towards developing 'green' nematicidal agents.

Abstract Root-knot nematodes (Meloidogyne spp.) are one of the most infective pests for a wide range of cultivated plants. The study was aimed to isolate chitinolytic soil bacteria, characterizing their properties, and to determine their in vitro antagonism against root-knot nematode eggs and juveniles. Out of the Ninety-five isolated strains, twenty-five gram-positive and non-hemolytic strains were selected and screened for production of extra-cellular enzymes, such as chitinase, protease, lipase, gelatinase, etc., as well as for biofilm formation, anti-fungal activity, and in vitro antagonism against root-knot nematodes. Eleven strains demonstrated broad anti-fungal activity against common plant pathogenic fungi, like Fusarium oxysporum and Alternaria alternata. Among the twenty-five strains, ten strains exhibited statistically significant (P˂0.05) second stage juvenile (J2s) percent mortality (>60 %) and inhibited egg hatching. The in-vitro activity of these ten strains was found to be correlated with their biofilm formation, enzyme production, and anti-fungal activity. Further, out of these ten strains, nine strains were assigned to the Bacilli group (99-100% similarity), and one was identified as Paenibacillus xylanilyticus (96 % similarity) after sequencing the gyrB gene. Overall, the present in vitro study suggested that the chitinolytic bacterial strains showing biofilm formation, enzyme production, and anti-fungal activity demonstrate an important trait to exhibit antagonism against root-knot nematodes.