DSE and its metabolites on Medicago sativa L. growth promotion and its potential for ecological restoration in mining areas

Coal mining has caused the reduction of land productivity in mining areas and exacerbated the problem of ecological fragility, while microbial combined plant reclamation technology is a commonly used means of ecological restoration in mining areas, and the appropriate inoculation method of microbial agents is of great significance for accelerating the ecological restoration in mining areas. Dark Septate Sndophytes (DSE) are a group of endophytic fungi ubiquitously existing in plant root systems, whose metabolites could function as plant growth stimulants. Taking Medicago sativa L. as the research object, four treatments were set up, including DSE hypha (HD), metabolite (MD), hypha and its metabolite (HD+MD) and blank control (CK), to explore the mechanism of DSE and its metabolite promoting effect on Medicago sativa L., under two inoculation methods of root dipping and simulated soil cultivation. The results showed that Medicago sativa L. co-treated with hypha and its metabolites under root dipping method had the best growth potential. Compared to the control group, the total biomass, total chlorophyll, root volume and total nitrogen content increased by 83.78%, 35.54%, 132.12% and 82.16%, respectively. The colonization rate of DSE in the root system of Medicago sativa L. could achieve 68.89%, dominated by the colonization in the hypha mode. Under simulated soil cultivation, DSE metabolites performed a significant growth-promoting effect on Medicago sativa L., and the colonization was dominated by the microsclerotia mode. The correlation analysis showed that compared with the inoculation method, the DSE inoculation treatment was significantly positively correlated with hypha colonization rate, microsclerotia colonization rate, total colonization rate, root length, root surface area, root projected area (P<0.05), and highly significantly positively correlated with aboveground fresh weight, root fresh weight, total fresh weight, root volume, total nitrogen and total potassium (P<0.01). DSE and its metabolites could regulate the growth of Medicago sativa L. through colonization rate and photosynthesis, providing a theoretical basis for the development and utilization of green microbial fertilizer for ecological restoration in mining areas.