Eco-friendly biocontrol of Phytophthora capsici in black pepper (Piper nigrum) using Burkholderia species

BACKGROUND AND OBJECTIVES: Phytophthora capsici is a devastating pathogen that causes significant yield losses in black pepper (Piper nigrum) globally. Given the need for environmentally safe alternatives to chemical fungicides, this study aimed to evaluate the antagonistic potential of rhizobacteria isolated from black pepper rhizospheres in Bangka and Sukamulya, Indonesia, to develop sustainable management strategies against Phytophthora capsici.METHODS: A total of 520 rhizobacterial isolates were screened using dual culture assays to assess their antagonistic activity against Phytophthora capsici. The isolates exhibiting strong inhibitory effects as more than 70 percent inhibition of radial growth were further characterized for their mechanisms of action, including enzyme production and volatile organic compound emission. Cryo-field emission scanning electron microscopy was used to study the morphological effects on Phytophthora capsici mycelia. Biosafety assays were conducted to evaluate hemolytic activity and hypersensitive response induction. Molecular identification of the most potent isolate was performed using 16 small subunit ribosome deoxyribonucleic acid sequencing. Greenhouse trials were conducted to assess the biocontrol efficacy of the identified isolate in reducing foot rot disease in black pepper plants.FINDINGS: Out of 520 isolates, 37 showed antagonistic activity, with ten isolates inhibiting over 70 percent of Phytophthora capsici radial growth. Isolate Burkholderia species demonstrated the highest inhibition as 87.59 percent, mediated through enzyme production and volatile organic compound emission. Cryo-field emission revealed significant morphological abnormalities in Phytophthora capsici mycelia, such as lysis and shriveling. Eight effective isolates were non-hemolytic and did not induce hypersensitive responses in tobacco leaves, confirming their safety for biocontrol use. Physiological characterization revealed the production of chitinase, glucanase, and protease enzymes by these isolates. Molecular identification classified Burkholderia species a known biocontrol agent. In greenhouse trials, Burkholderia species significantly reduced foot rot disease incidence, demonstrating its efficacy in controlling Phytophthora capsici.CONCLUSION: The findings conclusion demonstrate that Burkholderia species can serve as an effective and eco-friendly biocontrol agent, significantly reducing Phytophthora capsici infections. This study promotes sustainable agricultural practices and supports the use of biological control in integrated disease management systems, minimizing environmental impact and reducing chemical reliance.