Multiple Applications of Bacterial Based Biocontrol in Plant Protection

Plant pathogens and pests pose one of the greatest challenges to global food security due to the rapidly growing human population, while the changing global climate further exacerbates their negative impact on crop productivity. In order to comply with IPM regulations and achieve sustainable development in agriculture, it is imperative to explore new strategies for managing prevalent plant diseases and pests. Thus, we explored potential biocontrol bacteria strains from Xenorhabdus and Bacillus in order to identify effective biocontrol agents, which can serve as new resources for the development of biopesticides.
Plant fungal diseases represent a significant threat to crop production, not only by reducing product quantity and quality but also by posing serious health risks to humans and livestock due to mycotoxins. Fusarium head blight (FHB) and black scurf disease are epidemic fungal diseases caused by Fusarium graminearum and Rhizoctonia solani, respectively. The antifungal capacity of decades of Xenorhabdus strains was evaluated by bioassay targeting these two pathogens. Multiple genetic methods coupled with HRMS/MS analysis were applied to identify the bioactivity NPs (natural products) and their BGCs (biosynthetic gene clusters), while combinatorial strategies of genetic engineering and fermentation engineering were conducted to improve the yield of bioactivity NPs. XBD 14 and XBD 8 were found to exhibit remarkable antifungal efficacy against F. graminearum and R. solani, respectively, with fabclavine derivatives identified as the major antifungal compounds that significantly controlled these plant diseases in field tests.
To cope with deoxynivalenol (DON) contamination in cereals infected with FHB, we collected soil and wheat grain samples from FHB-affected fields, isolated new Bacillus strains from enriched solutions, and employed HPLC analysis to assess the DON degradation capacity of these isolates. The cultivation conditions were optimized to enhance the degradation ability of candidate strains, and the structure of the transformed products was determined through LC-MS and NMR analysis. Results indicate that Bacillus N22 and HN117 exhibited stable detoxification capacity, effectively transforming DON into less toxic derivatives.
Apart from using direct prevention techniques to control plant diseases and pests, enhancing plant immunity and resistance to pathogens and pests is a good concept for an indirect effect. Bacillus spp. are well-known plant-growth-promoting rhizobacteria (PGPR). Therefore, we investigated the inducible effect of a PGPR strain, Bacillus velezensis GA1, on broad bean resistance against Myzus persicae, which causes a huge loss in crop yield and economy by transmitting plant viruses. GA1 was found to have a positive effect on plant resistance against aphids, as evidenced by feeding behavior and fitness results.
In conclusion, the Xenorhabdus and Bacillus strains studied here have great potential as new bio-pesticides or additives for multiple applications in plant protection