Strain-Specific DSE Effects on Yam Rhizosphere Carbon Metabolism Are Modulated by Soil Factors

Rhizosphere microbes are vital for plant growth. Dark septate endophytes (DSE) can enhance host plant adaptability and regulate microbial communities, showing promise for yam soil remediation. This study examined how single and mixed inoculations of eight DSE strains affect yam rhizosphere carbon metabolism. Results showed that rhizosphere microbes preferred carbohydrate and amino acid carbon sources. Single inoculations exhibited relatively high overall metabolic activity, whereas mixed inoculations demonstrated distinct advantages in the utilization of specific carbon sources, such as carbohydrates. Key discriminators were phenolic acid, carboxylic acid, and carbohydrate utilization. Different strains enhanced specific pathways: Pe and Fu improved amine metabolism; Ac and Zo excelled in carbohydrate use; Pl boosted polymer metabolism. Changes in carbon metabolism correlated with soil properties: polymer and amine use with pH and SOC; carbohydrate use with AP; phenolic and carboxylic acid use with AN. Soil properties were also altered strain-specifically. The Pe strain emerged as the prime candidate for mitigating yam continuous cropping obstacles by synergistically improving both carbon metabolism and soil quality. These findings aid in developing biofertilizers and rhizosphere remediation strategies.