Combining Trichoderma sp. and biogenic AgNPs from Trichoderma strains as a synergistic control complex to improve the growth of muskmelon and suppress Fusarium oxysporum f. sp. melonis

Abstract

Muskmelon Fusarium wilt (MFW) disease caused by Fusarium oxysporum f. sp. melonis (FOM) is one of the major challenges faced in muskmelon production worldwide. Trichoderma sp., as a well-known biocontrol fungus, and AgNPs have been widely used to control plant diseases. However, few literature studies have been reported on the combined application of AgNPs and Trichoderma sp. against soil-borne diseases. This study was aimed at investigating the inhibitory effect of AgNPs and Trichoderma sp. to FOM and the control effect of the combined application of AgNPs and Trichoderma koningiopsis (TK) against MFW. The characteristics of different AgNPs were also analyzed using various techniques, such as XRD, TEM-EDS, FTIR and TEM. Results showed that TK had the highest inhibition rate (63.77%) against FOM among the four Trichoderma strains and had the best resistance to AgNPs, with an average inhibition rate of 5.76% on mycelium growth. Different AgNPs and their combinations had different inhibitory effects on the growth and sporulation of FOM. The inhibition rate of the AgNPs-TH (T. hamatum) and AgNPs-TK (T. koningiopsis) combination (AgNPs-C) was the highest, reaching up to 50.83%. The specific absorption peaks of AgNPs-TH, AgNPs-TK and AgNPs-C occurred at 420 nm, 323 nm and 320 nm, respectively. XRD and TEM-EDS showed that the crystalline structured nanoparticles were spherical with a diameter ranging from 16.5 nm to 23.4 nm. FTIR results showed that there were more functional group moieties (–OH, –CH₃, –C–O, etc.) on AgNPs-C, which were involved as a capping and reducing agent in the biosynthesis of AgNPs. The combined application of AgNPs-C and TK decreased the incidence (11.11%) and disease index (2.78) compared with CK-F (77.78% and 48.61, respectively) and improved the growth and plant fresh weight. Thus, the combined application of AgNPs and biocontrol agent (TK) could be used to improve the growth and development of muskmelon and suppress the MFW disease, providing an alternative approach to realize an eco-friendly control of the soil-borne disease.