<i>Trichoderma pubescens</i> Elicit Induced Systemic Resistance in Tomato Challenged by <i>Rhizoctonia solani</i>

<i>Rhizoctonia solani</i> causes severe diseases in many plant species, particularly root rot in tomato plants. For the first time, <i>Trichoderma pubescens</i> effectively controls <i>R. solani</i> in vitro and in vivo. <i>R. solani</i> strain R11 was identified using the ITS region (OP456527); meanwhile, <i>T. pubescens</i> strain Tp21 was characterized by the ITS region (OP456528) and two genes (<i>tef-1</i> and <i>rpb2</i>). The antagonistic dual culture method revealed that <i>T. pubescens</i> had a high activity of 76.93% in vitro. A substantial increase in root length, plant height, shoot fresh and dry, and root fresh and dry weight was indicated after applying <i>T. pubescens</i> to tomato plants in vivo. Additionally, it significantly increased the chlorophyll content and total phenolic compounds. The treatment with <i>T. pubescens</i> exhibited a low disease index (DI, 16.00%) without significant differences with Uniform^® fungicide at a concentration of 1 ppm (14.67%), while the <i>R. solani</i>-infected plants showed a DI of 78.67%. At 15 days after inoculation, promising increases in the relative expression levels of three defense-related genes (<i>PAL, CHS,</i> and <i>HQT</i>) were observed in all <i>T. pubescens</i> treated plants compared with the non-treated plants. Plants treated with <i>T. pubescens</i> alone showed the highest expression value, with relative transcriptional levels of <i>PAL, CHS</i>, and <i>HQT</i> that were 2.72-, 4.44-, and 3.72-fold higher in comparison with control plants, respectively. The two treatments of <i>T. pubescens</i> exhibited increasing antioxidant enzyme production (POX, SOD, PPO, and CAT), while high MDA and H₂O₂ levels were observed in the infected plants. The HPLC results of the leaf extract showed a fluctuation in polyphenolic compound content. <i>T. pubescens</i> application alone or for treating plant pathogen infection showed elevated phenolic acids such as chlorogenic and coumaric acids. Therefore, the ability of <i>T. pubescens</i> to inhibit the growth of <i>R. solani</i>, enhance the development of tomato plants, and induce systemic resistance supports the application of <i>T. pubescens</i> as a potential bioagent for managing root rot disease and productivity increase of crops.