Antagonistic Effect and Plant Growth Hormone Produced by Endophyte Bacillus amyloliquefaciens LKM-UL Isolated from Cocoa Plant

Abstract

In Malaysia black pod disease caused by Phytophthora palmivora is one of the serious problems causing yield loss in cocoa plantation. In this study, an endophytic bacterium living within tissues of healthy Theobroma cacao L. leaves was isolated and assessed its ability to inhibit the growth of P. palmivora. Based on molecular identification using 16S rDNA gene sequences analysis, this endophytic bacterium was identified as Bacillus amyloliquefaciens which was subsequently named as Bacillus amyloliquefaciens LKM-UL. Preliminary test using dual culture method showed B. amyloliquefaciens LKM-UL has strong ability to inhibit the growth of P. palmivora. B. amyloliquefaciens showed the highest antifungal activity after 24 h incubation in nutrient broth. Cells-free supernatant from B. amyloliquefaciens showed the highest antifungal activity of 30.6 mm with cell concentration of Log 10 10.63 CFU/mL via agar disc diffusion method. B. amyloliquefaciens LKM-UL also produced plant growth hormone identified as 1-naphthalene acetic acid (NAA), tryptamine, 3-indole propionic acid (IPA), indole-3-butyric acid (IBA), gibberellic acid (GA), trans-zeatin and kinetin.