Isolation and characterization of rhizobacteria, Bacillus spp. for controlling bacterial leaf blight and increasing shallot yield

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Xanthomonas axonopodis pv. alii (Xaa), which causes bacterial leaf blight on shallots, can cause yield losses both in quantity and quality to reach 100% if the environmental conditions are suitable for its development. Indigenous Rhizobacteria, Bacillus spp. reported to be effective for controlling plant diseases and can increase plant growth and yield. The study aimed to obtain Bacillus spp. isolates capable of controlling bacterial leaf blight and increasing the growth and yield of shallots. The study consisted of 3 stages. The first is the isolation of Bacillus spp. from soil and shallot roots in production centers and endemic areas of bacterial leaf blight in Solok and Agam districts, West Sumatra. The second is control of bacterial leaf blight with Bacillus spp. At this stage, research was experimental in the experimental garden of the Agriculture Faculty, Universitas Andalas, consisting of 43 treatments and three replications. The treatments consisted of 40 isolates of Bacillus spp., Streptomycin, control+(without Xaa and Bacillus spp.), and control – (Xaa inoculated, without Bacillus spp.). Bacillus spp. introduced to shallot seeds. Xaa is inoculated by wounding the surface of the leek using a sterile needle, then the Xaa suspension is applied to the injured area, and the plant is covered with clear plastic. The third is the identification and characterization of selected Bacillus spp. to control bacterial leaf blight and increase shallot yield. The results showed that nine isolates of Bacillus spp. increased the resistance of shallots to bacterial leaf blight from susceptible to resistant, and five isolates were also able to increase the yield of shallots by 388-433% compared to controls. Based on the molecular identification of the five isolates, MRTDE2.6 was B. subtilis BSn5; MRSNRZ1.2 is B. mycoides strain ATCC 6462; MRBPRZ1.1 is B. thuringiensis strain IAM 12077; MRRZLL2.2 is B. mycoides strain ATCC 6462, and MRRDE3.4 is B. weihenstephanensis strain ATCC 6457. Biochemical characteristics of 5 species of Bacillus spp. selected were three species produced siderophore, none made HCN, three species produced salicylic acid, two species had protease enzymes, three species produced ammonia, all produced biosurfactant, all were hemolysin negative, and all species produced IAA.