Effectiveness and Mechanism of Endophytic Bacillus in Suppressing Wilt Intensity of Banana Seedling Inoculated by Blood Disease Bacterium

Abstract

Background and Objective: The main constraint faced by the banana farmers in Indonesia is bacterial wilt caused by Blood Disease Bacterium (BDB). Biological control of the disease using endophytic Bacillus is promising to develop. This study aimed at reporting the experimental study of the effectiveness and mechanism of some endophytic Bacillus of banana in suppressing wilt intensity of banana seedling artificially inoculated by BDB. Materials and Methods: The study was conducted in greenhouse, using 10 isolates of endophytic Bacillus of banana and banana seedlings produced by tissue culture acclimated for 3 months. A unit of treatment consisted of three banana seedlings arranged by completely randomized design with three replications. Each seedling was planted on 1 kg of soil media infested by endophytic Bacillus and BDB at 108 CFU g–1. The pathogen inoculation was done on day 7 after Bacillus infestation. Some capability analyses of the isolates of producing growth regulator, enzymatic and chemical compounds were also done in vitro for supporting the study of antagonistic mechanism. Results: The results showed that some isolates of the endophytic Bacillus significantly (p<0.05) suppressed the infection rate and wilt intensity. The Bacillus reduced disease intensity by 51.44-24.07%. The antagonistic isolates reduced infection rate from 0.36 to 0.03-0.09 unit day–1. The significance was also showed by the Area Under the Disease Progres Curve (AUDPC) variable. The isolates produced Indole Acetic Acid (IAA) and grown positively on chitin and pectin medium. The volatile and nonvolatile compounds produced by the isolates inhibited growth of the pathogen significantly (p<0.05). Conclusion: Some isolates of endophytic Bacillus are promising as biological control agents of bacterial wilt of banana caused by BDB as they reduce wilt intensity effectively and they produce IAA, chitinase, pectinase, volatile and nonvolatile compound that are presumably involved in the antagonism mechanism.