<i>Fusarium oxysporum</i> f. sp. <i>lycopersici</i> (<i>Fol</i>) and <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> (<i>Foc</i>), are the causal agent of Fusarium wilt disease of tomato and banana, respectively, and cause significant yield losses worldwide. A cost-effective measure, such as biological control agents, was used as an alternative method to control these pathogens. Therefore, in this study, six isolates of the <i>Streptomyces</i>-like colony were isolated from soils and their antagonistic activity against phytopathogenic fungi and plant growth-promoting (PGP) activity were assessed. The results showed that these isolates could inhibit the mycelial growth of <i>Fol</i> and <i>Foc</i>. Among them, isolate STRM304 showed the highest percentage of mycelial growth reduction and broad-spectrum antagonistic activity against all tested fungi. In the pot experiment study, the culture filtrate of isolates STRM103 and STRM104 significantly decreased disease severity and symptoms in <i>Fol</i> inoculated plants. Similarly, the culture filtrate of the STRM304 isolate significantly reduced the severity of the disease and symptoms of the disease in <i>Foc</i> inoculated plants. The PGP activity test presents PGP activities, such as indole acetic acid production, phosphate solubilization, starch hydrolysis, lignin hydrolysis, and cellulase activity. Interestingly, the application of the culture filtrate from all isolates increased the percentage of tomato seed germination and stimulated the growth of tomato plants and banana seedlings, increasing the elongation of the shoot and the root and shoot and root weight compared to the control treatment. Therefore, the isolate STRM103 and STRM104, and STRM304 could be used as biocontrol and PGP agents for tomato and banana, respectively, in sustainable agriculture.

The tomato (Solanum lycopersicum L.) is one of the most important vegetables grown globally. However, the production of tomatoes is restricted by Fusarium oxysporum f. sp. lycopersici (Fol). This study aims to investigate the ability of Fol-resistant tomato genotypes to be a rootstock for the susceptible cultivar. In this study, a tomato cultivar was grafted on rootstocks of the same species (intraspecific), and grafting compatibility, peroxidase gene expression, and fusarium wilt disease incidence of tomato scion was evaluated. A Fol-susceptible tomato ‘Sidathip 3’ (SDT3) was grafted onto four different Fol-resistant tomato genotypes and compared with self-grafted cultivar/cultivar and rootstock/rootstock. The survival rate of all grafted plants was 100% at 20 days after grafting (DAG) without significant differences in incompatibility evaluated at 42 days after grafting. The expression of the peroxidase gene (Solyc02g084800.2) using the qPCR technique was compared in self-grafted rootstock LE472/LE472 and SDT3/LE472. The expression level was three times higher in heterografted plants than in self-grafted ones at 15 DAG, indicating graft incompatibility. The rootstocks did not affect the height of the plant, the number of branches, the size of the fruit, or the yield of SDT3 scion. All intraspecific heterografted plants significantly controlled Fol when evaluated 60 days after inoculation. These results showed the usefulness of intraspecific grafting by using the proper rootstock genotypes to increase pathogen resistance in addition to stimulating growth and fruit yield.