基于有机酸分泌的野生油茶对酸性土壤高铝低磷适应的植物-根际微生物互作机制

Al toxicity (high-Al) and P deficiency (low-P) are the primary factors limiting crop growth and production in acidic red soils. Previous studies mostly investigated them separately as independent factor, which made it difficult to fully reveal the adaptation mechanisms of plant to the high-Al and low-P environment. Wild oil tea (Camellia oleifera Abel.), one of oil crops, is widely distributed in acidic red soils in south of China,and has a strong tolerance to the high-Al and low-P environment. However, the adaptation mechanisms of oil tea to high-Al and low-P environment is still unclear. This project intends to research the characteristics of organic acid anions secretion under high-Al and low-P stress in wild oil tea which has a stronger tolerance to the high-Al and low-P than cultivar, and to inquiry into the relationship of the secretion of organic acids and the stress of high-Al and low-P under the actual soil conditions; Then, to study the population and abundance of rhizosphere microorganisms using molecular biological techniques, and to explore the molecular ecology of rhizosphere microorganisms related to high-Al and low-P stress; Finally, to analyse the interaction of microorganisms and organic acids between rhizosphere and non rhizosphere soil, based on the systematic research of the microbial adaptive mechanisms of high-Al and low-P stress. The objective of this project is to clarify the adaptation characteristics of oil tea in response to the high-Al and low-P stress based on secretion of organic acids. The results of this project can not only expound the adaptation mechanisms of oil tea to the high-Al and low-P stress in acidic red soil in theory, but aslo provide theoretical foundation and direction for the high-yield cultivation of oil tea in practice.

铝毒和缺磷是影响酸性土壤中作物生产的两个主要限制因素。以往的研究大多侧重单一的因子，不能全面揭示植物对酸性土壤高铝低磷适应的机制。野生油茶是我国南方酸性土壤上广泛分布的油料作物，对酸性土壤高铝低磷具有较强的适应性，但其对酸性土壤高铝低磷的适应机制仍不明确。本项目拟以存在抗性差异的两个油茶基因型为研究对象，研究高铝低磷对有机酸分泌特征的影响，探讨有机酸的分泌与磷铝胁迫浓度之间的关系；利用分子生物学技术研究高铝低磷下油茶根际微生物的种群及丰度，探讨胁迫条件下根际微生物的分子生态学特征；最后，在系统研究根际微生物高铝低磷胁迫适应性机制的基础上，探究油茶根际和非根际土壤中微生物与植物分泌有机酸的互作规律。通过本项目的研究，可望从有机酸分泌的角度阐明野生油茶对酸性土壤高铝低磷的适应机制。研究成果不仅可丰富酸性土壤上植物对铝毒和低磷的适应性机制，以期为油茶高产栽培提供理论依据。

项目以野生普通油茶和栽培品系为研究对象，运用野外调查采样、水培实验、盆栽实验相结合的方法，主要开展了以下工作：（1）研究了高铝低磷环境下油茶根际土壤与非根际土壤的细菌多样性，结果表明，Nitrospirae门丰度在野生油茶根际土壤与非根际土壤之间存在显著差异，同时野生油茶根际一些细菌种类与栽培品系赣油1号存在显著差异。（2）研究了高铝低磷胁迫对油茶幼苗生长及其根系有机酸分泌的影响。结果表明，在铝胁迫下，磷的加入能够显著降低铝的胁迫；而高铝低磷胁迫都会显著降低其根系分泌的总有机酸量，以及柠檬酸和苹果酸的含量。（3）研究了不同油茶品系细根功能性状及根际土理化性质的差异，结果表明，栽培品系（赣永6号油茶）相对于野生油茶和赣油1号油茶在养分吸收上更具有优势。根际土壤速效养分（SAK、Olsen-P、NH4+-N和NO3--N）含量与油茶细根各功能性状存在相关关系。（4）研究了野生油茶与栽培品系油茶对土壤养分和胞外酶的影响，结果表明种植野生油茶使土壤养分（有机质，全磷，有效磷和速效钾）含量和土壤磷酸单酯酶(AP)活性显著低于种植栽培品系，但是土壤纤维二糖水解酶(CB)活性显著高于栽培品系。（5）研究了高铝低磷环境下野生油茶和人工油茶从枝菌根真菌多样性研究，结果表明，野生油茶与栽培油茶根际AM真菌的总体组成存在显著差异，回归分析表明，环境因子对油茶根际丛枝真菌影响的大小依次为土壤酸碱度、铵态氮含量、有效磷含量、有机质含量；6种不同品系（赣无1、赣无24、赣永6、赣兴46、赣石84-8、野生）油茶种子内生AM真菌在属水平上的优势种为Paraglomus和unclassified_c_Glomeromycetes，其中有4个人工栽培品系和野生品系之间在OTU水平上存在显著差异物种；通过基于 Bray–Curtis距离的NMDS分析表明，野生普通油茶、浙江红花油茶与人工栽培普通油茶、浙江红花油茶林下土壤AM真菌群落组成存在明显差异。（6）从红壤丘陵区土壤中分离出了耐钇、耐铝、解磷等微生物菌株，并对其耐性特征进行了研究，揭示了不同耐性微生物的生理生化特征。