Benefits of Endophytic Fungus Phomopsis liquidambaris Inoculation for Improving Mineral Nutrition, Quality, and Yield of Rice Grains Under Low Nitrogen and Phosphorus Condition

The deficiency of N-P availability in soil is a primary cause for crop yield and nutrient loss. Since plant-beneficial microbial symbiosis is an eco-friendly method for compensating this negative effect, understanding the interconnection between endophytic fungus colonization and mineral nutrient accumulation in edible parts of crop is important in agricultural production. In this study, we focused on the effects of endophytic fungus Phomopsis liquidambaris on the absorption and distribution of 14 essential mineral elements in vegetative organs (root and shoot) and reproductive organs (grain) of rice during its growing period with reduced N-P fertilizer application, as well as the changes in yield, quality, and mineral nutrition of rice grains. The possible mechanisms including the transcriptional level of the transport-related genes and the structure of endophytic community were also investigated. The results indicated that the P. liquidambaris significantly increased the accumulation of N, P, Fe, Mn, Zn, Mo, and Se in rice grains by 20.5%, 18.9%, 18.2%, 9.5%, 17.9%, 13.3%, and 17.1%, respectively, accompanied by the significant increase in yield (23.8%) and protein content (17.3%). These beneficial effects were attributed to the enhancement formation of iron plaque, the upregulation of nutrient transporters genes, and the altered endophyte community by P. liquidambaris symbiosis. In conclusion, P. liquidambaris could promote the partition of nutrients to the grains by increasing the efficiency of nutrient uptake and remobilization. Our results suggest P. liquidambaris symbiosis as a useful candidate for improving the mineral nutrition, quality, and yield of rice grains under N-P-deficient field condition. Graphic Abstract