Understanding the role of Bacillus subtilis GEB1 in enhancing guava plant immunity against Meloidogyne enterolobii: A multifaceted approach

Abstract

Guava root-knot nematode, Meloidogyne enterolobii has emerged as a significant threat to guava cultivation, impacting production worldwide. By integrating the molecular, histopathological and in silico approaches the current study explores the efficacy of Bacillus subtilis GEB1 in enhancing the resistance of guava against M. enterolobii. The gene expression studies reveal that guava plants treated with B. subtilis and challenged with nematodes at 72 h showed 2 fold increase in phytoene synthase, 2.1 fold increase in mitogen-activated protein kinase, 1.54 fold increase in phenylalanine ammonia-lyase and 1.82 fold increase in peroxidase genes when compared to untreated control. The Scanning electron microscope analysis of guava roots treated with B. subtilis revealed the presence of spores in the rhizoplane region which led to deter the invading nematodes. The comparative histological studies with guava roots treated with B. subtilis revealed lesser damage in the cortex, vascular regions with limited hypertrophy and hyperplasia, lesser adult females, and feeding traces with minimum root, stele and cortex diameter and thickness than those of untreated infested roots. Attempts were made to dock the plant functional proteins with B. subtilis peptides to understand their interaction. The results revealed that bacillobactin showed a greater binding affinity of −9.0 kcal/mol with phytoene synthase, plipstatin (−16.0 kcal/mol), and fengycin (−15.9 kcal/mol) with MAPK proteins of guava. Overall, the current study offers insight into the intricate mechanisms of plant-nematode-bacteria interactions and underscores the importance of B. subtilis GEB-1 as a biocontrol agent to combat Meloidogyne enterolobii infection in guava.