Ralstonia solanacearum causes bacterial wilt disease in tomato and other crops resulting in huge economic losses worldwide. Several measures have been explored for the control of R. solanacearum, but the desired control level of the disease through sustainable and ecofriendly way is still awaited. In this study, fungal metabolites produced by Trichoderma harzianum were investigated in the form of crude extract for the management of R. solanacearum both in vitro and in planta in tomato plants. In in vitro investigation, fungal metabolites were checked for their antibacterial potential at different concentrations (30, 60, 90, 120, 150, and 180 mg ml−1) and bacterial cell morphology was observed under scanning electron microscopy (SEM). In a greenhouse experiment, different application times (0, 3, and 6 days before transplantation DBT) and doses (0, 3, 6, and 9%) of the fungal metabolites were tested for their effects on soil bacterial population, disease severity and plant growth of tomato plants. The in vitro evaluation showed a strong antibacterial activity of fungal metabolites in concentration dependent manner. The highest concentration 180 mg ml−1 produced maximum inhibition zone (20.2 mm) having non-significant difference with the inhibition zone (20.5 mm) produced by the standard antibiotic streptomycin. The SEM analysis revealed severe morphological destructions of bacterial cells. In case of greenhouse experiment, the highest decrease in soil bacterial population, lowest disease severity, and maximum increase in plant growth parameters were obtained by highest dose (9%) and longest application time (6 DBT). The fungal metabolites produced by T. harzianum could be used as low-cost, environment-friendly, and sustainable management strategy for the control of R. solanacearum in tomato plants.

中文翻译：

---

通过生物防治真菌哈茨木霉（Trichoderma harzianum）产生的代谢物对番茄中的青枯病进行生物防治

青枯雷尔氏菌引起番茄和其他农作物的细菌性枯萎病，在世界范围内造成巨大的经济损失。已经探索了几种控制青枯菌的措施，但是仍在等待通过可持续和生态友好的方式控制疾病的期望水平。在这项研究中，以粗提物的形式研究了哈茨木霉（Trichoderma harzianum）产生的真菌代谢产物，用于在番茄植物的体外和植物中管理青枯菌。在体外研究中，检查了真菌代谢物在不同浓度（30、60、90、120、150和180 mg ml-1）下的抗菌潜能，并在扫描电子显微镜（SEM）下观察了细菌的细胞形态。在温室实验中，不同的施用时间（DBT移植前0、3和6天）和剂量（0，测试了3％，6％和9％的真菌代谢物对土壤细菌种群，疾病严重程度和番茄植物生长的影响。体外评估表明真菌代谢物具有很强的抑菌活性，且呈浓度依赖性。最高浓度180 mg ml-1产生的最大抑制区（20.2 mm）与标准抗生素链霉素产生的抑制区（20.5 mm）无明显差异。SEM分析显示细菌细胞的严重形态破坏。在温室试验的情况下，通过最高剂量（9％）和最长施用时间（6 DBT）可获得最大的土壤细菌种群减少，最低的疾病严重度和最大的植物生长参数增加。哈茨木霉产生的真菌代谢物可以用作低成本，