Fungal Endophyte Phomopsis liquidambari Improves Iron and Molybdenum Nutrition Uptake of Peanut in Consecutive Monoculture Soil

Iron (Fe) and molybdenum (Mo) are essential trace elements for plants, especially for peanut. However, peanut planted in consecutive monoculture soil usually suffers from malnutrition. Thus, the objective of this study was to investigate the effects of the fungal endophyte Phomopsis liquidambari on Fe and Mo nutrition uptake of peanut in consecutive monoculture soil. Plant growth parameters, physiological parameters. the accumulation of Fe and Mo elements, gene expression related to absorption and transformation of Fe and Mo in planta, and the low-molecular-weight organic acids (LMWOAs) concentration in rhizosphere soil were analyzed by greenhouse pot experiments. The results showed that the application of P. liquidambari improved growth parameters, chlorophyll content, nitrate reductase (NR) activity, and Fe and Mo nutrition of peanut. Furthermore, LMWOAs in peanut rhizosphere soil and the expression levels of AhFRO1, AhIRT1, and AhMOT1 were significantly changed by the application of fungal endophyte. These findings indicated that the improvement of Fe and Mo nutrition in peanut was mostly derived from the promoting growth function of P. liquidambari and the regulation of peanut-P. liquidambari symbiosis with rhizosphere LMWOAs and Fe- and Mo-related gene expression in continuous monoculture soil.