Characterization and evaluation of the endophyte Bacillus B014 as a potential biocontrol agent for the control of Xanthomonas axonopodis pv. dieffenbachiae – Induced blight of Anthurium

Abstract

A Bacillus isolate (B014) demonstrating strong inhibition against the pathogen Xanthomonas axonopodis pv. dieffenbachiae (XAD) was obtained from healthy tissue of an Anthurium plant and was selected for further characterization. Based on the sequence analysis of the 16S rDNA gene and the gyrA gene, the Bacillus B014 isolate was identified as Bacillus amyloliquefaciens. Bacillus B014 was shown to produce anti-XAD metabolites that have a high resistance to a wide range of pH values, high temperatures and digestion by proteinase K. PCR-based detection showed that Bacillus B014 can potentially coproduce iturins and surfactins. Applying the Bacillus B014 cell suspension or its cell-free culture filtrate to the leaves of an Anthurium pot plant before challenge with the pathogen XAD decreased the percentage of leaves with lesions to 17.86% and 28.57%, the percentage of the leaf area with lesions to 7.86±1.25% and 18.14±1.44%, respectively, when compared to 96.30% and 49.85±1.58% in control Anthurium plants challenged only with the bacterial pathogen. The Bacillus B014 cell suspension or its cell-free culture filtrate also induced an increase in the activities of the defense-related enzymes phenylalanine ammonia lyase, peroxidase and polyphenol oxidase, when compared to control Anthurium plants challenged only with the pathogen. The Bacillus B014 cell-free culture filtrate also inhibited further disease development of Anthurium plants already demonstrating disease symptoms caused by XAD. In conclusion, the newly isolated B. amyloliquefaciens B014 is a promising candidate as a biological agent to control bacterial blight caused by XAD, particularly in the Anthurium plant.