The Potential of Cabbage Rhizosphere Actinomycetes to Control Black Rot Disease Caused by Xanthomonas campestris pv. campestris

Abstract

Actinomycetes are Gram-positive soil bacteria known for decomposing organic matter and producing secondary metabolites, such as antibiotics and hydrolytic enzymes, which contribute to pathogen suppression and soil health. This study aimed to isolation of actinomycetes from the cabbage rhizospheric and evaluate their antagonistic activity against X. campestris pv. campestris (Xcc), the causative agent of black rot disease in cabbage. The study consisted of four main stages: isolation, selection, characterzation, and identification of potential isolates. A total 55 actinomycetes isolates were successfully isolated from cabbage rhizospheric in Garut, Cianjur and Bandung, West Java. Among them, 16 isolates were non-pathogenic to plant and mammals. In vitro assays showed inhibition of Xcc by 3.96-20.83%. Seed germination and growth tests on cabbage revealed a vigor index of 41.7-88.3% and germination rate of 50.83-93.33%. Based on the Analytical Hierarchy Process (AHP) method, three isolates CPT5, CPT8, and SNT10 were identified as the most potential biocontrol agenst Xcc, as they exhibited peroxidase enzyme activity. Moleculer identification through 16S rRNA sequencing confirmed that CPT5 was identified as Streptomyces polychromogenes, CPT8 as Streptomyces vinaceus, and SNT10 as Streptomyces rochei. These findings indicated that actinomycetes from the cabbage rhizospheric have potential to control X. campestris pv. campestris.