丛枝菌根真菌促进油茶磷吸收的效应及分子机制研究

Camellia oleifera Abel is one of the important economic forest resources in South China, high yield and high nutrient use efficiency is the target of C. oleifera product. However, the contribution of arbuscular mycorrhizal fungi (AMF) to C. oleifera growth under field conditions remains unclear. Phosphorus element is an important nutrient factor to the growth of C. oleifera, in order to improving the transformation efficiency of lowly water-soluble phosphate, we needed further study the effects and mechanism of AMF on phosphrous uptake in C. oleifera. The projects include both field and pot experiments based on previous research and this seminar early research. Two field experiments of a 5 year nitrogen and phosphorus experimental site are selected. Spore isolation and molecular approach are combined to investigate the biodiversity of AMF in the different strains of C. oleifera field over the C. oleifera growth period. Spore isolation, rot colonization rate, plant P uptake and soil available P are determined spatially and temporally to investigate the contribution of AMF to P mobilization and uptake by C. oleifera palnts. Two compartments cultivation system and fluorescence quantitative are employed to analysis regulating effect of AMF on the transformation of soil organic P, and clarified the effects on the expression of phosphate transporter of C. oleifera and phosphatase activity and its gene by AMF, and revealed the molecular mechanism for AMF on phosphorus uptake in C. oleifera. The project has important significance in enriching mycorrhizal resources in our country and improving ecosystem productivity of C. oleifera, and provide theoretical evidence for the management of C. oleifera in the the high yield and high nutrient use efficiency.

油茶是南方地区重要经济林资源之一，高产高效是其生产的目标，而集约化油茶生产体系中菌根的作用尚不明确。磷是其生长的重要养分因子，为提高土壤难溶性磷的转化效率，需要进一步研究菌根促进油茶磷吸收的效应和作用机理。本项目在前人研究和本课题组前期研究基础上，选取定位施氮磷肥效应试验5年的油茶林，采集不同品系不同时期根系和不同土层的土壤样品，以孢子形态学结合分子生物学方法分析集约化油茶菌根真菌多样性的时空变化特征及其品系间差异性；原位检测菌根侵染率、植株磷含量和土壤有效磷的时空动态，探讨林间条件下菌丝对油茶吸收活化土壤磷的影响；通过分室隔网培养系统、荧光定量等方法和手段，分析AM真菌对油茶土壤有机磷转化的调控作用，阐明AM真菌对油茶磷转运子和磷酸酶活性及其基因表达量的影响，揭示菌根促进油茶磷吸收的分子机理，对丰富我国菌根资源和提高油茶林生态系统生产力具有重要意义，为油茶高产高效经营提供科学理论依据。

丛枝菌根真菌（AMF）能与80%以上的陆生植物形成共生关系，促进宿主对水分及营养元素，特别是磷的吸收，而集约化经营油茶根际土壤菌根菌资源及其对磷素吸收的作用机制尚未明确。本项目以油茶为研究对象，在盆栽试验、分室隔网培养系统和林间种植条件下，采用高通量测序技术、质谱技术、实时荧光定量PCR技术，探讨了原位条件下油茶不同品种根际土壤AM真菌多样性时空变化特征和AM真菌对油茶无机磷吸收的影响，并进一步探讨了AM真菌对油茶磷转运子和磷酸酶活性及其基因表达量的影响，揭示菌根促进油茶磷吸收的分子机理。研究结果表明，原位条件下下，AM真菌对油茶根系的丛枝侵染率为1.19%~14.46%，泡囊侵染率为4.70%~28.45%，菌丝侵染率为7.28%~59.93%；油茶根际AM真菌包含4目8科9属，其中相对丰度最高为Glomus(58.5%)；季节、品种和土层影响油茶根际AM真菌的alpha多样性，品种和土层影响AM真菌的群落结构；土壤因子中，NH4+和pH是影响油茶根际AM真菌群落结构的主要因子；盆栽试验和分室隔网培养系统中土壤进行灭菌处理，接种AM真菌能够增强油茶的光合能力，从而促进油茶的生长和物质积累；施有机磷处理提高了基质有机磷、有效磷含量和植株磷浓度，表明油茶能够利用有机磷；在相同的有机磷水平下，接种AM真菌提高了油茶总根长、根直径、根体积、根表面积和根系活力，增强了油茶根系及土壤磷酸酶活性和植酸酶活性，降低了基质有机磷和有效磷含量、增加了油茶植株地上部和地下部磷含量，表明AM真菌促进了土壤有机磷的转化；接种AM真菌和解磷细菌显著提高了土壤酸性磷酸酶、碱性磷酸酶、植酸酶活性；无论是否接种，油茶植株磷浓度随着供无机磷水平的上升而上升，在不同KH2PO4浓度下，接种AM真菌油茶植物磷浓度均显著高于未接种处理，且接种AM真菌降低了油茶Pht1相对表达量。本研究结果对丰富我国菌根资源和提高油茶林生态系统生产力具有重要意义。