College of Agricultural Sciences, International University of Business Agriculture and Technology, Dhaka, Bangladesh.
Department of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh.
PLoS One. 2022 Jun 8;17(6):e0267253. doi: 10.1371/journal.pone.0267253. eCollection 2022.
Southern blight of tomato caused by Sclerotium rolfsii can cause severe plant mortality and yield losses. The use of rhizobacteria for the biological control of Southern blight disease is a potent alternative to chemical fungicides. Although rhizobacteria are prolific candidates, comprehensive reports regarding their use in tomato disease management are limited. The present study screened six rhizobacterial strains for antagonism against S. rolfsii in dual culture and culture filtrate assays. The selected promising strains were tested further for plant-growth-promoting and biocontrol potentials under in vitro, greenhouse, and field conditions. Of the six strains screened, Stenotrophomonas maltophilia PPB3 and Bacillus subtilis PPB9 showed the superior performance displaying the highest antagonism against S. rolfsii in dual culture (PPB3 88% and PPB9 71% inhibition), and culture filtrate assays (PPB3 53-100% and PPB9 54-100% inhibition at various concentrations). Oxalic acid produced by S. rolfsii was significantly inhibited by both rhizobacteria and supported their growth as a carbon source. The strains produced hydrogen cyanide, chitinases, siderophores, biofilm, and indole acetic acid. They showed the potential to solubilize phosphate and fix nitrogen. Seed treatment with S. maltophilia PPB3 and B. subtilis PPB9 improved seed germination and tomato seedling vigour. Significant increases in plant growth, chlorophyll contents, and N, P, and K concentrations were attained in bacterized plants compared to non-treated controls. The application of antagonists on container-grown seedlings in a greenhouse environment and field-grown tomato plants reduced symptoms of damping-off and Southern blight. The sclerotial counts decreased significantly in these soils. Bacteria-inoculated plants had a higher yield than those in the non-treated control. Bacteria colonized the entire roots, and their populations increased significantly in the protected plants. The results show the potential capabilities of S. maltophilia PPB3 and B. subtilis PPB9 for growth promotion, nutrient acquisition, and biocontrol of southern blight disease in tomatoes.
番茄立枯丝核菌引起的南方疫病可导致严重的植物死亡和产量损失。利用根际细菌对南方疫病进行生物防治是替代化学杀菌剂的有效方法。虽然根际细菌是大量的候选者，但关于它们在番茄病害管理中的应用的综合报道是有限的。本研究在双培养和培养液测定中筛选了 6 株拮抗番茄立枯丝核菌的根际细菌。选择有前景的菌株在体外、温室和田间条件下进一步测试其促进植物生长和生物防治潜力。在所筛选的 6 株菌株中，产碱假单胞菌 PPB3 和枯草芽孢杆菌 PPB9 表现出优异的性能，在双培养（PPB3 抑制率 88%，PPB9 抑制率 71%）和培养液测定（PPB3 在不同浓度下 53-100%抑制，PPB9 抑制率 54-100%）中对 S. rolfsii 的拮抗作用最强。产碱假单胞菌产生的草酸对两种根际细菌的生长有明显的抑制作用，并作为碳源支持其生长。这些菌株产生氢氰酸、几丁质酶、铁载体、生物膜和吲哚乙酸。它们具有溶解磷酸盐和固氮的潜力。用产碱假单胞菌 PPB3 和枯草芽孢杆菌 PPB9 处理番茄种子可提高种子发芽率和番茄幼苗活力。与未处理的对照相比，接种细菌的植株的植物生长、叶绿素含量以及 N、P 和 K 浓度均显著增加。在温室环境中对容器中生长的幼苗和田间生长的番茄植株应用这些拮抗剂可减少猝倒病和南方疫病的症状。这些土壤中的菌核计数显著减少。接种细菌的植物比未处理的对照植物产量更高。细菌定植于整个根系，其种群在保护植物中显著增加。结果表明，产碱假单胞菌 PPB3 和枯草芽孢杆菌 PPB9 具有促进生长、获取养分和防治番茄南方疫病的潜力。
