Biological Control Ability and Antifungal Activities of Bacillus velezensis Bv S3 against Fusarium oxysporum That Causes Rice Seedling Blight

Abstract

Fusarium oxysporum, a primary soil-borne fungus that affects rice seedlings globally, is responsible for rice seedling blight (RSB), which reduces seedling quality and survival rates. The synthetic fungicides used to treat this disease negatively affect human health and the environment. A biocontrol bacterial isolate, Bacillus velezensis Bv S3, isolated from the rice rhizosphere, showed a strong antagonistic effect on RSB-causing F. oxysporum. The ratio of the longest to the shortest radius of F. oxysporum following Bv S3 inoculation was 2.52 (cm/cm) in a plate standoff experiment. This was different from the other biocontrol strains. Bv S3 exhibits a wide spectrum of antifungal activity against various pathogenic fungi that cause RSB. When 10% Bv S3 liquid culture filtrate was applied, it dramatically reduced F. oxysporum spore germination and mycelial growth, with inhibition rates of 66.7%, and 45.7%, respectively, and caused hyphal malformations. Furthermore, the Bv S3 suspension (1 × 108 CFU/mL) reduced RSB by 65.5% and 76.5% in pot experiments, effectively promoted the growth of rice seedlings, and improved the activities of neutral phosphatase, urease, invertase, and catalase in rice rhizosphere soil. The active substances produced by Bv S3 were sensitive to temperature and ultraviolet irradiation, and the antifungal effect significantly increased after 90 min of exposure, with antifungal effect observed at pH 7. Bv. S3 effectively reduced the incidence of RSB and showed potential as a biocontrol agent.

Exogenous GABA Enhances Copper Stress Resilience in Rice Plants via Antioxidant Defense Mechanisms, Gene Regulation, Mineral Uptake, and Copper Homeostasis

“…Seeds of the Ilmi rice cultivar ( Oryza sativa L.) underwent sterilization using Sportak fungicides [ 42 ] and multiple rinses with sterilized distilled water. They were soaked in water for four days at 32 °C in an incubator, as per Jan, R., et al [ 43 ].…”

Characterization of Biofertilization and Biocontrol Potential of Bacillus velezensis KHH13 from Organic Soils

“…The isolated bacteria were first identified at the genus level based on colony morphology. Subsequently, isolates exhibiting antibiotic activity were sent to the Food Industry Research and Development Institute of Taiwan for further identification using 16S ribosomal DNA (rDNA) and gyrase subunit B (gyrB) gene sequencing (Figures S1 and S2) [40]. Sequence alignment of 16S rDNA and gyrB gene regions was conducted using the maximum parsimony (MP) and maximum likelihood (ML) in MEGA 10.0 (Molecular Evolutionary Genetics Analysis) as described by Tamura et al [41] and subsequently analyzed by Bayesian inference, based on a Markov Chain Monte Carlo (MCMC) approach, was performed in MrBayes v.3.1.2 [42], with 1,000,000 generations, sampled every 100 generations.…”