Trichoderma asperellum M7 stimulates resident rhizobacterial consortia and alters the tomato fruit metabolic profile to enhance the sugar-acid ratio in postharvest tomatoes

• T. asperellum M7 enhances sugar acid ratio (SAR) in tomato by modulating soil microbes. • M7 impacts tomato metabolite synthesis pathways, increasing carbohydrate related compounds. • M7 boosts sugar metabolism enzyme activity and gene expression in tomatoes. Tomato ( Solanum lycopersicum L.), a globally cultivated fruit crop of the nightshade family, is highly valued for its broad dietary applications and health-promoting properties. In recent years, escalating consumer preferences for nutritious food options, coupled with rising disposable incomes and heightened awareness of dietary wellness, have significantly driven market demand for superior-grade tomato varieties. Consequently, enhancing fruit quality has emerged as a critical determinant in securing competitive advantages within the agricultural and horticultural sectors. Although using Trichoderma to improve fruit quality is an environmentally friendly approach, the microbial ecological mechanisms and the fruit metabolic profile by which Trichoderma inoculation affects fruit quality remain unclear. This study primarily explores the role of Trichoderma asperellum M7 in improving tomato quality from the perspectives of rhizosphere soil microbial communities and fruit metabolism, revealing its potential mechanisms. It was found that T. asperellum M7 enhanced the sugar-acid ratio of tomato fruits through the action of soil microorganisms, and this increase was significantly correlated with the genera TM7a and Candidatus _ Saccharimonas . Furthermore, the application of T. asperellum M7 was observed to significantly modulate metabolite synthesis pathways in tomato fruits. It notably enhanced the biosynthesis of carbohydrates and organic acid derivatives, with marked increases in specific compounds such as CDP-ribitol, d-glucose, cellobiose, and oxalosuccinate. Furthermore, strain M7 enhanced both the enzyme activity and gene expression associated with sugar metabolism in tomato fruits. Our research findings provided a new perspective on potential strategies for using microorganisms to enhance fruit quality.