Recently, the Soil-Plant Interaction Innovation Team of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) has made new progress in phosphorus nutrient recycling in green manures with research titled "Revealing the underlying molecular basis of phosphorus recycling in the green manure crop Astragalus sinicus", published in the Journal of Cleaner Production (IF="9.297").

According to Prof. Keke Yi, green manure is widely used in agricultural ecosystems and plays a vital role in the ecological restoration of degraded environments and in improving soil fertility. Milk vetch (Astragalus sinicus) is one of the most widely-used green manure varieties. The roots of leguminous green manure milk vetch can form root nodules with nitrogen-fixing bacteria and have a strong biological nitrogen-fixing ability. Turning milk vetch can reduce the loss of active nitrogen and increase the soil nitrogen nutrient cycle.

Given the excessive application of phosphorus fertilizers and the consequent environmental pollution risks, how to improve the phosphorus absorption capacity of green manure with nitrogen fixation ability, achieve high accumulation of nitrogen and phosphorus nutrients in green manure, and further improve the nitrogen and phosphorus recycling in the agricultural ecosystem is a problem that limits the development of the green manure industry.

In this study, different varieties of milk vetch were selected, and the physiological indexes of the vetch were evaluated under the condition of different phosphorus levels. An elite cultivar Xinzi-1, with high phosphorus efficiency, was identified. Xinzi-1 has a high tolerance to phosphorus starvation, and its phosphorus content is about 25% to 60% higher than other varieties. In both low-phosphorus and high-phosphorus environments, a higher level of phosphorus accumulation was observed in Xinzi-1, indicating that Xinzi-1 has a high ability to activate and accumulate phosphorus.

The study further analyzed the molecular mechanism of high phosphorus efficiency in this variety through spatiotemporal full-length transcriptome analysis, and found that the phosphorus signaling pathway network of Xinzi-1 changed globally under phosphorus deficiency. Under phosphorus starvation conditions, the expression profiles of core genes involved in phosphorus transport and signal transduction in Xinzi-1 changed significantly, and the expression of genes such as phosphate transporters and acid phosphatase was induced considerably, increasing activated soil phosphorus and phosphorus absorption capacity. At the same time, vacuolar phosphorus efflux genes were significantly up-regulated to release vacuolar phosphorus storage for plant growth. Finally, the study proposes an improved model based on the synergistic and efficient recycling of nitrogen and phosphorus between leguminous green manure and main crops.

The study identified the phosphorus-efficient milk vetch cultivar Xinzi-1, analyzed its molecular mechanism of phosphorus-efficiency, and accumulated important materials and experience for breeding improvement and field management of phosphorus-efficient milk vetch in the future. The study also provides new ideas for the efficient recycling of nitrogen and phosphorus nutrients of green manure crops in sustainable agricultural ecosystems, as well as the rational utilization, breeding, and variety evaluation of green manure crops.

The study was funded by the Science and Technology Partnership Program of the Ministry of Science and Technology, the Green Manure Industry Technology System, and the Science and Technology Innovation Project of the Chinese Academy of Agricultural Sciences.

Paper link: https://www.sciencedirect.com/science/article/pii/S0959652622005625

Lab website link: https://yilab.life/