Dachaihu Decoction

In recent years, pepper wilt has emerged as a pivotal constraint on pepper yield augmentation. Bacillus velezensis S3-1, with a wide array of hosts, can be used as both a biocontrol agent and biofertilizer. Nonetheless, the precise mechanisms underpinning its employment in combating pepper wilt remain cloaked in ambiguity. In our study, we found that B. velezensis S3-1 could significantly inhibit Fusarium sp. F1^T that caused pepper wilt. S3-1 could effectively inhibit both the growth and germination of F1^T conidia, leading to a reduction in the spore germination percentage from 83.2 to 37.1% in vitro experiments. Additionally, leaf detachment experiments revealed that the volatile compounds produced by S3-1 could inhibit the spread of pepper leaf spot area. Moreover, we observed a significant decrease in the content of malondialdehyde (MDA) in pepper treated with S3-1, along with a significant increase in the content of soluble protein, polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia-lyase (PAL) in pepper. Furthermore, RT-PCR analysis showed that the expression of the defense genes CaPR 1 and CaPIN II in pepper after treatment with S3-1 was significantly upregulated, suggesting that S3-1 had the potential to induce systemic resistance in pepper, thereby enhancing its disease resistance. Hence, our findings suggest that S3-1 can be a promising biocontrol agent for managing pepper wilt in modern agriculture.

Actinomycetes are an important microbial resource closely related to human production and life. Approximately 70% of the antibiotics currently used are produced by various actinomycetes. Pine wilt disease (PWD) is caused by the pine wood nematode (PWN) (Bursaphelenchus xylophilus), which is a devastating forest pest that can cause the wilting and death of pine trees. The purpose of this work was to screen out, identify, and ferment active actinomycetes with high lethality to pine wood nematodes and study the active compounds in their secondary metabolites. A group of 227 original strains/isolates of actinomycetes was screened, and Streptomyces sp. TCS19-048 was selected for further analyses. The taxonomic characteristics and molecular analysis results indicated that the strain was a member of the genus Streptomyces and exhibited the highest similarity (99.77%) with the 16S rRNA gene sequences of Streptomyces lactacystinicus OM-6519. Furthermore, the active extract was isolated and had an inhibitory effect on the movement behaviour of B. xylophilus and was able to significantly increase the body fluid leakage of B. xylophilus. This study focused on isolating secondary metabolites from various soil actinomycetes to control PWD and identified an extract with nematicidal activity from a selected strain. The nematicidal effect of extract S-3-1 was confirmed, and the strain Streptomyces sp. TCS19-048 showed good inhibitory activity against B. xylophilus, which was reported for the first time at home and abroad.