Potential of Local Bacillus spp. Isolates as Wilt Disease Biocontrol Agents for Fusarium (Fusarium oxysporum f. sp. cepae) on Wakegi Onions (Allium x wakegi Araki)

The use of biological agents as a biocontrol against plant pathogens was often ineffective because it worked slowly. The objective of this research was to examine the potential of local isolates of Bacillus spp. as a biocontrol agent in suppressing Fusarium wilt disease (Fusarium oxysporum f. sp. cepae) on wakegi onions. The research was designed using a completely randomized design with the treatment of rhizosphere bacterial isolates. The treatments consisted of control (without isolate application), isolates KP17, KP5, DB9, DB12, DB18, DG4, and DG11 so that the number of treatments was eight. Each treatment was repeated 5 times and each replication consisted of 10 wakegi onion plants. This research was divided into 2 stages, namely laboratory research which included isolation, characterization of colony morphology of rhizosphere bacterial isolates, and in vitro testing of the inhibitory power of biocontrol agents against pathogens. The test in the greenhouse was in the form of a disease case suppression test. The results obtained seven candidate isolates of biocontrol from 46 isolates obtained from the rhizosphere of the wakegi onion. These isolates had similarities with Bacillus spp. based on colony morphology, physiology, and biochemistry characteristics. Among the isolates found, the DB12 isolate had the potential to be developed as a biocontrol agent compared to other isolates.