Induced Resistance Mechanism of Twisted Disease Suppression of Shallot by Bacillus spp.

Abstract

Plant Growth Promoting Rhizobacteria has been known for its ability to induce plant resistance on shallot against twisted disease. Its ability as a bioprotectant agent is estimated to be comparable to the efficacy of Trichoderma which is currently widely used as a biological control agent.. This study aims to determine the content of jasmonic acid, salicylic acid, peroxidase, and disease suppression in shallot by application of Bacillus velezensis B-27, Bacillus cereus RC76, and application with combination of both rhizobacteria. The application was carried out with tuber dipping for 30 minutes in each treatment with a bacterial density of 108 CFU mL-1. Application using Trichoderma was used as the comparison treatment, and the control plot was not given any treatment. Pathogen inoculation was carried out simultaneously as planting using Fusarium acutatum with a spore density of 106 CFU mL-1. The jasmonic and salicylic acids content was measured using the High-Performance Liquid Chromatography method, and the peroxidase content was determined using the spectrophotometric method. Disease suppression was measured at 10-day intervals. The results showed that treatment with Bacillus cereus RC76 increased jasmonic and salicylic acid levels, while application with Bacillus velezensis B-27 showed the highest level of peroxidase. Treatments with Bacillus spp. were able to suppress twisted disease by 72.2% to 100%. This study demonstrated that application Bacillus spp. suppressed twisted disease on shallot and increased the jasmonic and salicylic acid content as induced resistance mechanism against pathogens.

Response of Five Shallot Varieties Applied with Bacillus spp. Against Twisted Disease

“…The suppression of twisted disease based on the disease intensity of five shallot varieties in all treatments ranged from 71.85% to 77.78% (Table 3). The ability of B. velezensis B-27 and B. cereus RC76 in combination to suppress twisted disease in the greenhouse, based on the study by Wulan et al (2022) showed that the twisted disease intensity was reduced by up to 90% with the bulb-dipping method.…”

“…The bulbs of five shallot varieties were dipped in a bacterial combined suspension of B. velezensis B-27 and B. cereus RC76 at a density of 10 8 CFU/mL with a ratio of 1:1. Each variety was dipped in 300 mL of the bacterial combination added to 3000 mL of water for 30 min, then air-dried (Wulan et al, 2022). The five shallot varieties were then planted in beds with a spacing of 20 × 15 cm.…”

The Diversity of Shallot Rhizomicrobiome and Twisted Disease Suppression with The Applicationof Bacillus spp. and Trichoderma asperellum

“…Furthermore, the treatment of B. velezensis had 71% similarity of fungal community compared to the treatments of B. cereus RC76 at the beginning of planting can induce plant resistance and suppress twisted disease by enhancing the accumulation of jasmonic acid (Wulan et al 2022). Jasmonic acid can activate plant resistance through the ISR signalling pathway, which causes priming for enhancing host defence gene expressions such as pathogenesis related (PR) 1, PR2, PR5, and plant defensin (PDF 1.2) (Niu et al 2011).…”

Utilization of Arbuscular Mycorrhizal Fungi and Bacillus velezensis Inoculation in Suppressing Twisted Disease of Shallot

“…The use of B. velezensis by soaking and spraying application by Rahma et al (2020), reported that B. velezensis was able to suppress twisted disease and purple spots development on shallot plants by 67% and increase plant growth and protect shallot bulbs postharvest. Wulan et al (2022) reported that the use of B. velezensis reduced disease development by 89%, with disease intensity and incidence of 4% and 4%, respectively.…”