Isolation and Performance Testing of Bacillus subtilis As Biological Agents to Control the Diplodia Disease on Siam Citrus

Abstract

This study aims to determine the feasibility of the Bacillus subtilis isolate as a biological agent and the concentration of bacterial cells capable of controlling Diplodia in the Siamese citrus (Citrus nobilis). Isolation and biological agency testing on soil samples taken from horticultural land were carried out at the UMSIDA Microbiology Laboratory. The trial of the biological agency application was carried out in Talok Village, Dlanggu District, Mojokerto Regency. The application experiment was carried out in a randomized block design, with treatment in the form of bacterial cell concentrations in the application volume consisting of no biological agents, 10−7, 10−8, and 10−9 CFU.ml−1 in 100 ml. The experiment was repeated five times in order to obtain 20 experimental units. The experimental data were analyzed by ANOVA at 5% followed by the 5% HSD test. The results showed that the bacterial isolates of B. subtilis were found to be potential biological agents with the white rhizoid-shaped colony and dry surface, gram-positive, and non-pathogenic in nature. Biological agent B. subtilis with a cell concentration of 10−8 CFU.ml−1 in 100 ml of application solution gave the best effect to reduce the intensity of Diplodia disease in C. nobilis.