Establishment of the Genetic Transformation System of Trichoderma longibrachiatum 40418 and Its Induced Resistance Against Meloidogyne incognita in Tomato

Trichoderma longibrachiatum is a filamentous fungus that functions as a biocontrol agent against multiple plant diseases. However, the lack of a genetic transformation system has hindered studies on gene function and the underlying biocontrol mechanisms in this species. In this study, protoplast preparation conditions were optimized using single-factor experiments and response surface methodology, yielding 2.05 × 107 protoplasts/g. PEG-mediated transformation yielded a GFP-labeled strain (GFP-40418). This strain enhanced resistance against Meloidogyne incognita, with root galling decreased by 47.6%. Treatment with GFP-40418 enhanced the activities of antioxidant enzymes, including PAL, POX, SOD, PPO, APX, and CAT. Plants treated with GFP-40418 alone showed the highest expression value, with relative transcriptional levels of PR2, Pal1, LOX, MYC2, ETR1, and ACO1 that were 29.62, 5.76, 7.30, 3.64, 4.79, 9.99-fold higher in comparison with control plants, respectively. These findings provide a genetic platform for exploring the gene functions of T. longibrachiatum 40418 and validate its biocontrol prospect against root-knot nematodes.