Characterization of plant growth-promoting rhizobacteria from black pepper rhizosphere: Antinomic activity and field efficacy of Pseudomonas isolate KBPf16

A random survey was undertaken to collect the rhizosphere soil samples from major black (Piper nigrum) pepper growing in highly elevated areas of Tamil Nadu to isolate and evaluate the native strains of Plant Growth Promoting Rhizobacteria (PGPR), with a focus on their antinomic activity and potential to enhance crop growth. 100 rhizobacterial strains were isolated, of which six were identified as Pseudomonas spp. (KBPf23, KBPf16, BBPf16, BBPf22, YBPf17, and TBPf21), demonstrating significant growth-promoting and antinomic properties. Among these, the strain KBPf16 showed the highest antagonistic activity against Meloidogyne incognita, a root-knot nematode. Under pot culture conditions, the talc-based formulation of native Pseudomonas isolate KBPf16 recorded a significant increase in plant growth parameters, viz., plant height, shoot weight, root length, and root weight by checking nematode population in root and soil. The result of the field trials confirmed that KBPf16, applied as a talc-based formulation (20 g/vein in two splits), significantly reduced nematode populations and enhanced yield parameters in black pepper, increasing the yield to 3578.7 g/vein compared to the chemical control (2456.2 g/vein). Additionally, plants treated with KBPf16 exhibited elevated levels of defense-related enzymes, including peroxidase, phenols, polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL), along with enhanced lignification in roots. These findings suggest that the cold-tolerant strain KBPf16 holds great potential as a biocontrol agent for sustainable nematode management and growth promotion in black pepper cultivation.