磷高效转基因水稻土壤磷形态及其有效性研究

Plants require large amounts of phosphate (Pi) to maintain growth and development. However, Pi is often a limiting factor for plants because of its low availability in the soil, which is mainly due to its low abundance and easy chelation with cations or organic compounds to form insoluble complexes. Rice (Oryza sativa) as one of the most important grain crops is also affected by Pi availability. Its productivity is seriously affected by Pi availability. It is well known that Pi-efficient transgenic rice increases the use efficiency of phosphorus, attracting widespread attention by the majority of plant nutritionists and genetic breeders. However, the effects of Pi-efficient transgenic rice on the soil nutrient and ecosystem function have not yet been carefully studied, it is important to evaluate the potential risks of Pi-efficient transgenic rice to agro-ecosystems. In this study, the characteristics of phosphorus fractions and activation characteristics of different forms of phosphorus in rhizosphere of different phosphorus efficiency rice are investigated. By sand culture, root box and field experiment, Pi-efficient transgenic rice (OsPT4, PHO2), high phosphorus efficiency rice (S. ANDREA, hualingdao) and low phosphorus efficiency cultivars (Lindao 1, Changnongjing 1) are used to evaluate the differences in pH, acid phosphatase, dry matter weigh, phosphorus accumulation, water soluble phosphorus, organic P fractions, inorganic P fractions under different P application rates. Finally, we will try to investigate the influence mechanism of the continuous Pi-efficient transgenic rice planting on different forms of phosphorus and Pi availability, which will provide technique support to evaluate the soil ecosystem safety of Pi-efficient transgenic rice.

土壤缺磷是限制植物生长的主要因素之一，水稻作为重要的粮食作物，其养分吸收尤其是磷素吸收极大的受到土壤有效磷的制约。磷高效转基因水稻以其对土壤磷素的高效吸收利用优势，受到广大植物营养学家和遗传育种学家的广泛关注。但是目前关于养分高效利用转基因作物种植对土壤养分循环影响的相关研究较少，其潜在的土壤环境风险无法预测。本项目以实验室已有的磷高效转基因水稻（OsPT4和PHO2）及其亲本非转基因水稻（日本晴）、磷高效常规水稻（S. ANDREA和花岭稻）、低磷敏感水稻（临稻1号和常农粳1号）为材料，利用不同形态磷素添加试验、根盒试验及3年的连续大田栽培试验，采用农业化学分析方法研究磷高效转基因水稻对土壤pH值、酸性磷酸酶、有效磷、土壤无机磷和有机磷形态组分变化及吸收的影响，揭示磷高效转基因水稻根际土壤磷形态及其有效性特征，为科学评价磷高效转基因水稻的土壤生态安全性提供相关技术支撑。

磷高效转基因水稻OsPT4的土壤磷素吸收量增加，势必会打破土壤中磷素的原有平衡，进而可能会影响土壤无机磷组分及土壤细菌群落的变化，因此，其外源基因对土壤环境的动态变化及养分空间分布的影响已成为转基因作物环境风险性评估中一项重要内容，本课题系统研究了种植磷高效转基因水稻OsPT4后植株磷素分布状况、土壤磷素动态变化及土壤细菌群落结构等，主要研究结果如下：.在盆栽条件下，⑴ OsPT4和PHO2根和叶的磷吸收效率、茎的磷利用效率以及磷转运效率均显著大于日本晴。⑵OsPT4和PHO2水稻根际土壤无机磷组分含量表现Ca10-P>O-P>Ca8-P>Fe-P>Al-P> Ca2-P，有机磷浓度表现为中活性有机磷浓度>中稳性有机磷>高稳性有机磷>活性有机磷，且各时期根际土壤的不同磷形态含量和同期日本晴相比均差异不显著。⑶ OsPT4和PHO2根际土壤磷酸酶活性和同期日本晴相比均无显著差异。.在红壤根盒栽培条件下，⑴ OsPT4和PHO2水稻根际和非根际土壤无机磷组分含量均表现为O-P>Fe-P>Al-P>Ca-P。 ⑵施磷处理时，OsPT4和PHO2的根际土壤O-P、Ca-P含量显著低于Nipp，其非根际土壤Al-P、Fe-P和O-P含量也显著低于Nipp。⑶不施磷处理时，OsPT4和PHO2的根际土壤Fe-P含量和非根际土壤Fe-P、O-P含量均显著低于Nipp，其根际土壤Ca-P含量显著高于Nipp。说明在供磷条件下，磷高效转基因水稻对A1-P、O-P和Ca-P的吸收活化能力较强，而缺磷条件下，磷高效转基因水稻可促进其根系对Fe-P的吸收利用。 .在田间小区施磷和不施磷栽培条件下，⑴同一生长期 OsPT4和PHO2的土壤全磷含量与日本晴均无显著差异，OsPT4的土壤Ca8-P、Al-P含量在抽穗扬花期、成熟期均显著低于日本晴。不施磷条件下，OsPT4土壤Ca2-P 含量在抽穗扬花期、成熟期显著低于日本晴。⑵同一处理、同一生长期内磷高效转基因水稻OsPT4、磷高效突变体水稻PHO2与常规水稻日本晴的土壤细菌16S rDNA DGGE指纹图谱基本相似。⑶在个别生长期，磷高效转基因水稻OsPT4对土壤细菌丰富度（S）、香农-威纳指数（H）和均匀度（EH）产生显著影响。