不同生育时期水稻土壤细菌群落特征与生态功能预测

Soil Bacterial Community Characteristics and Ecological Function Prediction at Different Rice Growth Stages

分蘖期和拔节—孕穗期是水稻产量构成要素中穗数和穗粒数形成的2个关键生育时期,氮素影响分蘖成穗和穗粒数的形成,细菌是土壤氮素循环的重要参与者。以高产水稻品种Y两优900和早丰优69为试验材料,通过设置2个氮肥施用比例(基蘖肥和穗粒肥比例分别为7∶3和6∶4),分析了分蘖期和拔节—孕穗期土壤细菌数量、群落特征的差异,及其与水稻产量、土壤氮素的关系。结果表明,水稻的分蘖期和拔节—孕穗期土壤细菌群落结构存在差异;分蘖期和拔节—孕穗期稻田土壤细菌优势菌门是变形菌门、拟杆菌门、绿弯菌门和酸杆菌门等。分蘖期绿弯菌门的相对丰度比拔节—孕穗期高6.16百分点,酸杆菌门的相对丰度比拔节—孕穗期高2.65百分点;拔节—孕穗期的变形菌门相对丰度比分蘖期高0.69百分点,拟杆菌门相对丰度比分蘖期高1.09百分点。相关性分析发现,水稻产量与分蘖期土壤细菌数量呈显著负相关关系,而与拔节—孕穗期土壤细菌数量和全氮含量均呈显著正相关关系;有效穗数与分蘖期土壤细菌数量呈显著正相关关系,穗粒数与分蘖期、拔节—孕穗期的氨氧化潜势均呈显著正相关关系。冗余分析(RDA)结果表明,稻田土壤细菌群落结构受多种因素共同影响,分蘖期土壤的铵态氮和拔节—孕穗期土壤的氨氧化潜势是显著影响稻田土壤细菌群落结构的2个环境因子。FAPROTAX功能预测进一步说明,分蘖期7∶3处理的反硝化功能增强,其中Y两优900土壤细菌的反硝化功能最强。因此,分蘖期土壤细菌数量的增加可提高水稻有效穗数。拔节—孕穗期土壤细菌参与的氨氧化作用可促进水稻穗粒数的增加。高产水稻品种Y两优900和早丰优69在不同施氮比例下,产量、有效穗数和穗粒数的形成与土壤细菌数量、群落组成及其生态功能关系密切。

Tillering stage and jointing—booting stage are important for the formation of panicle number and spikelets per panicle of rice,respectively.Nitrogen application affects the formation of panicle number and spikelet per panicle.Bacteria involve in soil nitrogen cycle.Two high-yield rice varieties,Y Liangyou 900 and Zaofengyou 69,were used to study the difference of soil bacterial number and community structure between tillering stage and jointing—booting stage,and the relationship between them and soil nitrogen,rice yield under two application ratios of nitrogen fertilizer(7∶3 and 6∶4 application ratios of basic tiller fertilizer to panicle-spikelet fertilizer).The results showed that there were significant differences in the structures of dominant bacterial groups in paddy soil between the tillering stage and jointing—booting stage,which were mainly Proteobacteria,Bacteroidetes,Chloroflexi and Acidobacteria.The relative abundance of Chloroflexi at the tillering stage was 6.16 percent points higher than that at the jointing—booting stage.The relative abundance of Acidobacteria at the tillering stage was 2.65 percent points higher than that at the jointing—booting stage.The relative abundance of Proteobacteria at the jointing—booting stage was 0.69 percent points higher than that at the tilling stage.The relative abundance of Bacteroidetes at the jointing—booting stage was 1.09 percent points higher than that at the tillering stage.The results of correlation analysis showed that rice yield was significantly negatively correlated with the number of soil bacteria at the tillering stage,but significantly positively correlated with the number of bacteria and total nitrogen content in the soil at the jointing—booting stage.There was a significant positive correlation between the number of effective panicles and the number of soil bacteria at the tillering stage.The number of spikelets per panicle was significantly positively correlated with the ammonia oxidation potential at the tillering stage and the jointing—booting stage.Redundancy analysis(RDA)showed that the bacterial community structures were affected by many factors.The contents of soil ammonium nitrogen and the ammonia oxidation potential were the main factors affecting the bacterial community structures at the tillering stage and the jointing—booting stage,respectively.The function prediction of FAPROTAX further indicated that the denitrification in the 7∶3 treatment at the tillering stage was enhanced,especially in the soil of Y Liangyou 900.Therefore,increasing the number of soil bacteria at the tillering stage could enhance the number of effective panicles.Ammonia oxidation involved by soil bacteria at the jointing—booting stage can promote the increase of spikelets per panicle in rice.For the high-yielding rice varieties,Y Liangyou 900 and Zaofengyou 69 under different nitrogen application ratios,the formation of yield,effective panicle number and spikelets per panicle is closely related to soil bacterial number,community composition and ecological function.