Synergistic Interactions Between Plant Growth-Promoting Bacteria and Trichoderma virens Enhance Arabidopsis Growth and Suppress Fusarium brachygibbosum

Trichoderma virens and plant growth-promoting bacteria (PGPB) are well-known agents that promote plant development and control pathogens. This study assessed the compatibility, biocontrol potential, and plant growth promotion of T. virens in combination with four PGPB strains (Pseudomonas fluorescens UM270, Rouxiella badensis SER3, Bacillus velezensis AF12, and Bacillus halotolerans AF23) against Fusarium brachygibbosum and Arabidopsis thaliana. The results showed that single inoculations significantly inhibited the growth of F. brachygibbosum by the 7th day of confrontation. However, co-inoculating T. virens with PGPB exhibited synergistic effects on the inhibition percentages for the consortia Tv + UM270 (48.94%), Tv + AF12 (67.04%), and Tv + SER3 (78.63%). Plant assays demonstrated that most microorganisms enhanced root development and plant height, with UM270 having the strongest beneficial effect. Expression analysis of T. virens effector genes (sm1, tvsep3, and tvhydii1) indicated early induction of tvhydii1 in the condition of Fb + AF12 at day 3, while sm1 was downregulated. No significant changes in the expression of these genes were detected during interaction with A. thaliana and PGPB. These findings demonstrate that T. virens–PGPB can simultaneously promote plant growth and suppress pathogens, with effector genes such as tvhydii1 contributing to these interactions, highlighting their potential for sustainable agriculture.