Mortierella elongata's roles in organic agriculture and crop growth promotion in a mineral soil

The addition of organic amendments contributes substantially to improvements in soil quality and prevents soil degradation. However, very little is known about the responses of dominant fungal strains to organic fertilizers or their functions in the nutrient transformations and crop growth promotion. Here, soils and maize roots were collected from a 35-year field experiment treated with composted soybean cake. The fungal communities in the bulk soil, rhizosphere, and endosphere were analyzed by deep amplicon sequencing of the internal transcribed spacer region gene. Overall, the soil fungal community was dominated by the phyla Ascomycota, Basidiomycota, and Zygomycota. Organic amendments changed the fungal community composition, with significant increase in the relative abundances of Mortierella, Fusarium, and Chaetomiceae in the bulk and rhizosphere soils. Mortierella elongata was the most successful fungi responding to organic inputs as seen by the surge in abundance. Genome characteristics of M. elongata indicated that M. elongata possessed the functional capacity to degrade a range of toxic organics, and thereby improve soil health. Furthermore, M. elongata's capacity to compose recalcitrant substances that can contribute to pools of long-term stable SOM was confirmed. These findings suggest that M. elongata may be mechanistic in sequestering C in soil. Inoculations of M. elongata into soil significantly increased the levels of plant indole acetic acid and plant biomass. Soil phosphatase and beta-glucosidase activities were also improved. Our study suggests that M. elongata can defend against soil degradation, improve soil health, and stimulate production of plant growth hormones.