不同耕作方式对当归根际土壤细菌群落多样性的影响

摘要

该研究以甘肃省中部渭源县大豆—当归轮作地、连作3年的当归地和荒地植物根际土为材料,采用PCR?RFLP法研究不同耕作方式下根际土壤细菌的群落多样性.应用 CTAB?SDS 法提取土壤微生物总DNA,建立土壤菌群16S rRNA基因克隆文库.用HaeⅢ,HhaⅠ和HinfⅠ对阳性克隆子进行酶切指纹图谱分析,测序并绘制系统进化树.经过初步分析,荒地、轮作地和连作地三者之间根际土壤细菌群落在种群数量和多样性上无显著差异,但在组成结构上存在明显差异,尤其是轮作和连作地.结果表明:轮作地和荒地的优势种群均为变形菌门,连作地的优势种群是拟杆菌门.进一步分析发现,对农作物有利的鞘脂单胞菌属(属于变形菌门)仅在轮作和荒地中出现,而在其他作物连作障碍中出现的无色杆菌属(属于拟杆菌门)仅在当归连作地中出现.因此,不同耕作方式对土壤细菌的群落组成结构影响较明显,土壤细菌群落组成结构的变化可能是当地当归连作障碍的重要原因之一;而轮作可有效提高根际土壤中细菌群落组成的多样性,并使有益细菌种群增加,改善土壤微生态环境,有效防止当归根腐病的发生.%Angelica sinensis is a genuine regional drug in the Gansu Province of China,continuous cropping obstacles se?riously affect the yield and quality of angelica in recent years. In this paper,the rhizosphere soil was sampled from the fields of Angelica?soybean rotated, angelica continuous cultivations and wasteland in Weiyuan County of Gansu Province. We aimed to know the differences of community structure and diversity of bacteria population in the three sam?pling sites,and provide some useful advises for the reasonable planting of angelica.The method of 16s rRNA PCR?RFLP (polymerase chain reaction?restriction fragment length polymor?phism)was used for the comparative analysis of rhizo?sphere bacterial community structure and diversity. The total DNA was extracted from the soil microbes by CTAB?SDS method and 16S rRNA gene cloning library was established.The fingerprints were analyzed by restriction fragment length polymorphism(RFLP)by using the HaeⅢ,HhaⅠand HinfⅠrestriction enzymes,respectively. Then phylogenetic tree was set up according to the 16S rRNA sequences.After preliminary analysis,there was no significant difference in bacte?ria population quantity and diversity indices of rhizosphere soils among wasteland,rotated planted fields and continuous cultivation fields,but there was very obvious difference in community structure of bacteria among the three fields,espe?cially in rotated planted fields and continuous cultivation fields.The results showed that the dominant population of bac?teria was Proteobacteria in rotation fields and wasteland,while the dominant population of bacteria was Bacteroidetes in continuous cultivation fields of angelica.The strains of Sphingomonas that belonged to Proteobacteria,which were benefi?cial to the growth of crop, appeared only in the rotation fields and wasteland, and the Achromobacter that belonged to Bacteroidetes associated with the continuous cropping obstacle appeared only in the continuous cropping fields. Our re?sults suggested that the different ways of angelica cultivation play an important role in bacteria community structure. Meanwhile, the continuous cropping obstacle might be associated with the changes of bacterial community structure in rhizosphere soils of cropped angelica. In conclusion, we think that the rotation can effectively enhance the composition of the bacterial community structure,increase the beneficial bacterial population,improve the soil microen?vironment,and prevent the root rot of angelica.