Biocontrol potential of five Burkholderia and Pseudomonas strains against Colletotrichum truncatum infecting chilli pepper

Abstract

ABSTRACTThe effect of bacterial antagonism against the causal agent, Colletotrichum truncatum was assessed as a potential alternative in managing anthracnose in chilli pepper. Out of 104 contrasting bacterial colonies isolated from rhizosphere soil of a forest floor, five isolates caused the radial growth inhibition greater than 90% (Significant at p < 0.05 level) of C. truncatum in dual cultures. Based on 16S rRNA analysis, these antagonistic bacterial isolates were identified as Pseudomonas aeruginosa, Burkholderia arboris, Burkholderia gladioli and Burkholderia rinojensis. The selected promising antagonists showed nearly 100% inhibition of the spore germination of C. truncatum in vitro. These antagonists produced antifungal compounds which are diffusible in nature. Microscopic studies of blackened fungal hyphae, which were subjected to antagonism showed many deformations such as thickening, swelling and malformation. In vivo study revealed that C. truncatum inoculated chilli pepper seeds treated with the five antagonists significantly inhibited the incidence of seed colonisation (p < 0.05) by the pathogen. At the post emergence stage, the survival percentages and vigour indices of all the antagonists’ treatments, except B. rinojensis strain 1, were significantly higher compared to the untreated control. The efficacy of the selected antagonists in managing anthracnose fruit rot was 100% at the colour breaking stage of chilli pepper fruits. These bacterial antagonists had a negative effect on C. truncatum spore attachment and subsequent colonisation on chilli pepper leaves except in the treatment of B. arboris. The results of in-vitro and in-vivo studies, suggest that the screened antagonistic bacterial isolates are potential biocontrol agents and need to be further studied for the biochemical basis of their activity against C. truncatum.