EXPLORATION OF ANTIMICROBIAL COMPOUNDS FROM STREPTOMYCES S9 AGAINST A PHYTOPATHOGEN, CORYNESPORA CASSIICOLA ( BERK & CURTIS)

Abstract

The present study was carried out to explore potential antimicrobial compounds from Actinomycetes against common plant pathogens. Actinomycetes were isolated from different environmental samples and screened for antifungal activity against Corynespora cassiicola (Berk & Curtis), the causative agent of target spot disease in tomato plants. Among the isolates screened by the dual culture plate assay, an isolate S9 exhibited highest percent in vitro growth inhibition (85.5%) against C. cassiicola. This isolate was identified as Streptomyces albolongus based on morphology, biochemical characteristics and 16S rDNA sequencing. Two antimicrobial compounds were extracted and purified from culture filtrate of potent isolate S9 by Thin layer chromatography TLC, column chromatography and High Performance Liquid Chromatography (HPLC) techniques. Fourier transform infrared spectroscopy (FTIR), Mass Spectroscopy and Nuclear Magnetic Resonance spectroscopic investigations revealed the identity of compounds as propyl ester of Octadec-9-enoic acid and 17-hydroxy, 27-methoxy natamycin. The Minimum Inhibitory Concentration (MIC) of these compounds against several plant pathogens was recorded. Pure compounds exhibited broad spectrum antimicrobial activity. In vivo studies in tomato plants revealed the efficacy of purified compounds in controlling target spot disease caused by C. cassiicola.