Characterization of antagonistic–potential of Bacillus velezensis SK71 against bacterial brown spot on a terrestrial orchid (Habenaria lindleyana)

Abstract

© 2020 Association of Agricultural Technology in Southeast Asia. All rights reserved. Bacillus velezensis SK71 was isolated from the rhizosphere of a terrestrial orchid. The result showed that SK71 has strongly inhibited Acidovorax avenae subsp. cattleyae. Isolate SK71 produced a 22 mm inhibition zone against A. avenae subsp. cattleyae in paper disc culture plate confrontation on nutrient yeast dextrose agar plates. The antagonistic bacterial isolate was identified by using 16S rRNA sequence analysis. PCR detection of the sfp and ituA genes coding for iturin A and surfactin, respectively, indicated a potential for the production of these antibiotics. The production of hydrolytic enzyme and the plant growth–promotional attribute of SK71 confirmed this multifaceted potential. The mixture formulation of SK71 with diatomite powder as a carrier and carboxymethyl cellulose, K2HPO4 and glucose showed good effect in suppressing the pathogen in vitro. Bulb treatment and spraying with these formulation is an effective delivery system that can provide a conducive environment for B. velezensis SK71 to suppress brown spot disease on the terrestrial orchid. Greenhouse studies revealed that SK71 had a 53.34% efficacy in controlling brown spot disease. In this study, we consider that formulation of SK71 is a promising natural biocontrol product, with scale–up possibilities for health and growth promotion of terrestrial orchids.