大豆-小麦长期轮作下小麦磷吸收利用的根际微生物驱动机制

The major demands of agricultural supply-side structural reform in China are keeping stability of wheat production, reducing corn production and increasing soybean, promoting cereal-legume rotation. However, we do not know whether phosphorus uptake in wheat in soybean-wheat rotation were higher than in maize-wheat rotation and microbial mechanism are not yet clear. Our previous illumina Miseq high through sequence studies showed that bacterial communities composition in wheat rhizosphere in soybean-wheat rotation were different from those in maize-wheat rotation. Metagenomic study showed that phytase gene (β-propeller phytases, BPP), pyrroloquinoline-quinone synthase C (pqqC) and alkaline phosphatase gene (phoD) with high relative abundances existed in soybean-wheat rotation soil. Surrounding the scientific problem of enhanced bioavailability and uptake of phosphorus in crops by rhizosphere microorganisms, the following studies will be investigated with rhizosphere ecology and modern molecular biology techniques: (1) the law of phosphorus uptake and utilization in wheat in the pot culture, to reveal the important role of microorganisms in phosphorus uptake under soybean-wheat rotation using microbial inhibition technology; (2) the law of phosphorus uptake in wheat and the driving factors in the field experiment; (3) the abundances of key functional genes of pqqC、phoD and BPP with real time fluorescence quantitative PCR technique, the community structure of key functional microorganisms containing genes of pqqC、 phoD and BPP in wheat rhizosphere with high throughput sequencing technology; The rhizospheric microbiological mechanism of efficient phosphorus utilization of wheat in soybean-wheat rotation would be elucidated. The results provide scientific basis for adjusting the agricultural planting structure and improving phosphorus utilization efficiency.

稳定小麦，调减玉米，增加大豆，促进粮豆轮作是我国农业供给侧结构改革的重大需求。相比玉米-小麦轮作，大豆-小麦轮作是否促进小麦磷吸收及微生物机制尚不清楚。前期研究发现，两种轮作模式下小麦根际细菌群落有所差异。大豆-小麦轮作土壤存在植酸酶基因BPP、葡萄糖脱氢酶基因pqqC和碱性磷酸酶基因phoD。围绕根际微生物是否促进作物磷吸收的科学问题，本项目应用微生物学和分子生物学方法，拟研究以下内容：（1）利用盆栽试验结合微生物灭菌技术，研究小麦磷吸收利用规律，揭示微生物在大豆-小麦轮作下小麦磷吸收的重要性；（2）利用田间小区试验，解析大豆-小麦轮作下小麦磷吸收变化规律；（3）利用实时荧光定量PCR技术测定小麦根际磷转化关键功能基因pqqC、phoD和BPP丰度，应用高通量测序技术分析功能微生物多样性，阐明大豆-小麦轮作下小麦磷吸收的根际微生物驱动机制，为调整农业种植结构，提高磷利用效率提供科学依据。

磷是小麦生长必需的大量元素，但磷肥施入土壤后易与矿物结合不易被植物吸收利用，为保证植物营养需求而施入的大量磷肥会通过地表径流造成水体富营养化等环境问题，同时加剧了全球磷资源的短缺。通过根际微生物溶解土壤无机磷和矿化有机磷为植物所利用成为减施增效的有效途径。调减玉米，增加大豆，促进粮豆轮作是我国种植业调整的重点。由玉米-小麦轮作转为大豆-小麦轮作后小麦磷吸收利用情况如何，根际微生物对小麦磷吸收发挥了什么作用尚不清楚。本项目设计了不同轮作和施肥处理的盆栽试验，测定了灭菌和正常情况下土壤有效磷、小麦生物量和磷吸收含量，比较分析了其差异，明确了根际微生物在小麦磷吸收中的促进作用。进一步测定了盆栽小麦根际土壤磷转化功能基因phoD、pqqC和BPP的数量，解析了pqqC基因与小麦生物量的相关性，进一步明确了根际磷转化功能基因对小麦生长发育的促进作用。通过田间试验研究了不同轮作小麦生长发育状况，发现了玉米-小麦轮作高施肥量对小麦磷吸收的抑制作用，阐明了轮作和生育期对小麦生物量和磷吸收的显著影响。通过研究磷转化功能基因数量及其功能微生物群落结构和多样性，明确了轮作和生育期对小麦根际功能微生物群落和组成的影响，阐明了Hydrogenophaga与Roseivivax与小麦生物量和磷吸收的相关关系，以及phoD、pqqC和BPP基因与小麦根际土壤有效磷、生长发育与磷吸收的相关性，探索了根际微生物及其功能基因phoD、pqqC和BPP对轮作的响应和对小麦磷吸收的促进机制，研究结果为调整种植业结构，促进农业供给侧结构改革，减施增效提供了科学依据。