Influence of different amelioration methods for replant peach orchards on phosphorus-dissolving microbial composition as well as yield and quality of yellow-fleshed peaches

【Objective】Peach, which is rich in vitamin C, antioxidants, dietary fiber and other nutritional elements, is a favorite fruit of Chinese people. Peach is grown in a large area and is a kind of fruit with both nutritional and economic values. However, peach industry is suffering from serious restricts by continuous cropping obstacle. Due to the short economic life of peach trees, most peach orchards require annual renewal. Thus, we need to overcome the obstacles of peach tree replanting disease. Although deep tillage could expand the shallow tillage layer, facilitate deeper rooting and increase resource availability in the subsoil layer, subsoil may not undergo weathering and lack of available nutrients. In addition, the primary plant productivity is typically limited by bioavailability of soil P, despite the abundant total P, after soil was deeply tilled. The aim of the experiment is to reduce the effect of peach replant obstacle on the growth of newly planted peach trees, and understand the soil properties,phosphorus microbial community composition and the interaction between peach yield and quality, and soil properties-phosphorus microbial composition.【Methods】In this study, three treatments, including untreated old peach orchard (CK), deep tillage and one year fallowing (DT) and deep tillage combined with one year rice planting (DT + RP) were applied to evaluate the effect of different methods on soil physical and chemical properties, and phosphorus-dissolving microbial composition. We analyzed soil physical and chemical properties, fruit weight and sugar content of yellow-fleshed peach with different treatments after four years. In addition, Illumina Miseq sequencing was applied to determine soil phosphorus-dissolving microbial composition and diversity by targeting phoD gene. In addition, the partial least squares path modeling was applied to analyze the relationship among soil physical and chemical properties, phosphorus-dissolving microbial composition, and peach yield and quality.【Results】The results showed that different treatments changed the physical and chemical properties of soil, and increased soil pH by 4.2% and reduced soil EC value by 74.7%, compared with CK treatment, respectively. But we did not find that soil nutrients contents significantly changed among different treatments (p> 0.05). DT treatment did not significantly affect soil absolute abundance of phoD gene, while DT + PR treatment significantly reduced the abundance of phoD gene in soil by 51.8% compared to the CK. Correlation analysis showed that phoD gene abundance was significantly and positively correlated with EC value and available phosphorus content, while significantly and negatively correlated with soil organic matter content. The different improvement methods did not significantly change the soil phosphorus-dissolving microbial richness index (ACE and Chao) and Sobs, but significantly changed the diversity index. DT treatment reduced the soil Shannoneven index by 1.96%, while DT + PR treatment increased the Shannoneven index by 1.44%. Bradyrhizobium, Nocardioides, Cupriavidus and Rhizobacter as the dominant phoD were contained in the microorganisms, and the relative abundance of Bradyrhizobium and Cupriavidus increased. Different improved methods increased the yield of yellow- fleshed peach, with DT and DT + PR treatments increasing the yield by 7.1% and 13.8% than CK, respectively. DT treatment increased fruit sugar content by 18.8%, while DT + PR treatment only increased by 5.4%, compared with CK treatment. Different improved methods decreased the titratable acid of yellowfleshed peach fruit, and DT and DT + PR fruits decreased by 21.5% and 27.9% compared with CK, respectively. Partial least squares path modeling showed that different improvement methods can directly change the yield and sugar content of yellow-fleshed peach by changing the soil physical and chemical properties (R = -0.855, p＜0.05), or indirectly affect the abundance and composition of soil phosphorusdissolving microorganisms to affect the yield and sugar content of yellow- fleshed peach. In addition, soil physicochemical properties can directly change the abundance of microorganisms (R = 1.30, p＜ 0.05) and composition (R = -0.890, p＜0.05), which in return, the abundance of soil phosphorus microorganisms (R = -0.614, p＜0.05) and composition (R = 0.953, p＜0.05) significantly affected the yield and sugar degree of yellow-fleshed peach, respectively.【Conclusion】This study showed that the combination of deep tillage and rice plantation can changed soil physical and chemical properties, improved the microbial diversity of phoD containing microorganisms and changed the composition of phoD containing microorganisms. Different improvement methods changed the community composition of phosphorus microorganisms, and the deep tillage combined with planting rice improved the relative abundance of Bradyrhizobium and Cupriavidus, which may play an important role in improving soil nutrient content. In addition, our results also showed that the soil physical and chemical properties caused by different improvement methods directly affected the yield and sugar content of yellow- fleshed peach, which can be also affected indirectly by the changing of abundance and composition of phoD contain-ing microorganisms caused by different improvement methods. Our results provide reference for soil improvement of yellow-fleshed peach replanting, and provide a viable method for the sustainable development of yellow-fleshed peach industry