Evaluation of the biocontrol potential of endophytic bacteria isolated from Coffea liberica (w. Bull ex hiern) against brown eyespot-causing fungal phytopathogen

Abstract

Aims: The study aims to investigate the potential of the endophytic bacteria as an alternative to control the devastating brown eyespot disease caused by Cercospora sp. in coffee plants. The fungal phytopathogen causes severe leaf fall and berry damages resulting in serious yield losses in coffee farms in the Philippines and worldwide. Currently, the management of this fungal infection relies heavily on synthetic fungicides, which may be of major environmental concern. Methodology and results: Endophytic bacteria were isolated from the intercellular tissues of Coffea liberica leaves by surface sterilization, maceration, dilution technique, plating on trypticase soy agar and colony characterization. Fourteen isolated endophytic bacteria were screened for their ability to inhibit the mycelial growth of Cercospora sp. through modified dual culture assay. Isolates HCC10-3 SC3, HCC10-3 SC2, HCC10-1 SC1, ICC10-3 SC1, and ICC10-1 SC1 yielded the highest percent inhibition of radial growth (PIRG) with 59.56%, 60.92%, 60.96%, 64.36%, and 67.06% respectively and are statistically significant (p<0.05) compared to the antibiotic control nystatin. The top five performing endophytic bacteria were subjected to hydrolytic enzyme production assays and found to exhibit amylolytic, lipolytic, proteolytic, chitinolytic, and cellulolytic activities. Based on the morphological and molecular identification by the 16S rRNA sequence analysis, isolates showed the similarity with Staphylococcus cohnii, Bacillus siamensis, Staphylococcus hominis, and Kosakonia cowanii found in GENBANK. Conclusion, significance and impact of study: The study revealed the biological control potential of endophytic bacteria agents against the brown eyespot-causing fungus in coffee.