轮作休耕下耐旱春小麦品种根际偏好微生物与抗旱机理研究

Many experiments show that crop rotation and fallow system combining with rational cultivation can protect and improve effectively the soil environment, and affect microbial community diversity of soil. The microbiome in the rhizosphere plant roots plays a key role in plant growth and health, enhancing nutrient availability and protecting plants from biotic and abiotic stresses, and then increases soil productivity and crop yield. Now, it has not been reported that spring wheat species are treated with crop rotation and fallow system combining with drought stress. Our previous studies and preliminary experiments show that microbiome, treated with crop rotation and fallow system combining with drought stress, in the rhizosphere wheat roots were significant specificity. Here, in northern areas of the Greater Khingan, 3 drought tolerant spring wheat species and 3 water sensitivity species are treated with crop rotation and fallow system combining with drought stresses, the interaction between different spring wheat species and the relevant soil microorganism is systematically researched by high-throughput sequencing and bioinformatics. It is focused on the drought tolerant spring wheat species -rotation and fallow system influence the soil microbial community and its change rule is uncovered. And then, the microbes response mechanism of spring wheat species under drought stress is revealed. The correlation analysis of spring wheat drought tolerance related genes and the specific soil microbes is analyzed, and it is aimed at obtaining beneficial microbes of soil improvement and yield increase and their cooperative drought resistance mechanism . It can provide theoretical and technical support for increasing soil fertility and ecosystem restoration in arid regions.

研究表明轮作休耕结合合理的耕作措施，能有效地保护和改善土壤环境，影响土壤微生物的多样性，且作物根际微生物能影响作物生长发育、增强养分有效利用、抵御逆境危害等，进而提高土壤生产力和作物产量。目前，轮作休耕结合干旱处理对耐旱春小麦品种根际微生物多样性与抗旱机理的研究未见报道。前期研究结果和预实验表明轮作休耕结合干旱处理下耐旱春小麦品种根际微生物具有显著的特异性。在大兴安岭北麓地区，以3种耐旱品种和3种水敏感品种为研究对象，进行6种轮作休耕模式结合干旱处理，利用高通量测序与生物信息学相结合手段，对春小麦不同品种与土壤微生物的偏好关系进行系统研究。重点开展轮作休耕下耐旱春小麦品种根际微生物多样性的变化规律；探索干旱处理下其微生物响应机制；分析春小麦抗旱基因与特异微生物的关联性；以期获得土壤改良和小麦丰产的有益微生物及其协作抗旱机制，为旱区农田地力提升和生态系统恢复提供理论依据和技术支撑。

本文从作物-土壤-微生物互作体系的角度，利用qPCR、紫外吸收光谱法等分子生物学，扩增子、宏基因组、转录组、代谢组等高通量测序与生物信息学相结合的方法，开展了水分、温度及氮肥对农田土壤微生物多样性的影响，轮作休耕结合干旱处理对春小麦根系土壤微生物群落结构的影响及有益菌株筛选与功能验证，气候对春小麦生长发育的影响等方面的研究。主要结果如下：（1）水分、温度对土壤微生物群落多样性具有显著影响（P<0.05）。干旱胁迫下放线菌门丰度显著增加，细菌对温度更加敏感；17年的田间数据表明，在一定程度上气温的提高有利于冷凉地区小麦籽粒产量提升，开花前温度提升，有利于春小麦分蘖，增加穗数，显著提高籽粒产量（P=0.0093）。（2）轮作休耕结合干旱处理下春小麦品种与微生物具有显著的偏好（P<0.05），且与微生物的丰度与基因表达之间存在显著关联（P<0.05）。耐旱春小麦能够增加放线菌门、厚壁菌门和奇古菌门等根际抗旱相关有益微生物相对丰度和根系分泌物含量，促进内质网中的蛋白质加工、淀粉和蔗糖代谢、苯丙烷生物合成等信号转导通路的TaXTH-7A、TaWlip19、TaWdreb2、TaBADHb等关键基因高效表达，调节水分和养分循环动态平衡，有利于抵御干旱危害，尤其春小麦-休耕-马铃薯模式下春小麦表现最佳，揭示了轮作休耕下春小麦根际微生物对干旱的响应机制。（3）施氮水平和方式对根际微生物群落结构具有显著影响（P<0.05），且不同空间位置微生物多样性和群落组成差异显著，呈非根际>根际>根内的趋势，真菌组成比细菌组成对施氮量更敏感，180kg/ha施氮量和基肥60kg/ha+追肥60kg/ha有利于提高土壤放线菌门、亚硝化螺菌属及马赛菌属等有益微生物的相对丰度，调节了土壤硝化作用等功能类细菌，有利于作物对土壤养分的高效利用。（4）筛选出5株秸秆高效降解和高抗性的候选菌株，其中树状微杆菌BZ15纤维素降解效率高，生理生化性能稳定，经生理生化及形态学分析，该菌株呈不规则杆状，菌落表面光滑，为酶活性高的喜氧型革兰氏阳性菌。全基因组测序分析表明其基因组上存在大量与纤维素降解酶有关的基因（内切葡聚糖酶和β-葡萄糖苷酶），初步揭示了BZ15的纤维素降解机制。研究结果为大兴安岭沿麓作物品种、轮作休耕模式和微生物有机肥开发等农田地力培育和可持续发展提供了数据支撑和理论依据。