Isolation and screening of actinomycetes active against plant pathogenic fungi

This paper mainly focuses on the isolation and screening of actinomycetes from the south coast of Yogyakarta, which has bioactivity against plant pathogenic fungi. Actinomycetes with bioactivity against Phytophthora palmivora, a plant pathogenic fungus that causes fruit rot disease, was isolated and screened. The medium used for the isolation was starch casein mixed with antifungal compound of nystatin (25 µg/mL) and cycloheximide (75 µg/mL). The samples were pretreated by heating them for 15 minutes at 65℃. Bioactivity assay of the plant pathogenic fungi was conducted using the disc diffusion agar method. From the experiment, 36 isolates were obtained from 30 sediment samples. Two isolates, RS001.05, and RS003.04 showed inhibitory activity against the growth of the cocoa plant pathogenic fungi Phythopthora palmivora. RS001.05, which showed higher activity, was selected to be identified using DNA molecular identification. Microbial identification and characterization showed that RS.001.05 was actinobacteria, part of the genus Streptomyces, and part of the Streptomyces sp. with a homology was 99%. The phylogenetic tree showed that RS001.005 isolate was part of the same group as Streptomyces indonesiensis and Streptomyces malaysiensis.