Potential of Bacillus spp. against root-knot nematode, Meloidogyne enterolobii parasitizing chili (Capsicum annuum L.)

Abstract

The root-knot disease caused by root-knot nematodes, Meloidogyne spp. poses a serious threat in economic crops worldwide, causing substantial economic losses. Chemical-based pesticides are the most commonly employed measure to manage root-knot diseases in chili and other crops. In this study, four Bacillus strains were identified as biocontrol agents against M. enterolobii. The cell-free culture filtrates (CF) and cell suspension (CS) of the Bacillus were prepared and tested to determine their efficacy against M. enterolobii, as compared to abamectin (a nematicide) and distilled water. The CF derived from all strains showed the greatest potential, equivalent to abamectin, in controlling M. enterolobii. Results evidenced a 92%–94% reduction in nematode hatching and 99–100% increase in second-stage juvenile mortality, compared to the untreated control. In addition, Scanning Electron Micrograph (SEM) observations showed abnormality in nematode cuticles treated with CF of the bacteria. Similar results were found in the greenhouse experiments where CF of all strains significantly reduced the number of galls, egg masses and eggs per gram root. These Bacillus spp. displayed a potential for effectively controlling M. enterolobii, probably due to their ability to produce nematode cell wall degrading enzymes, i.e., protease and lipase. In conclusion, our study indicates that the Bacillus strains studied can be utilized effectively to manage M. enterolobii, the causal agent of chili root-knot disease.