间作大豆对甘蔗根际土壤细菌及固氮菌多样性的影响

为探讨间作大豆(Glycine max)对甘蔗(Saccharum officinarum)根际土壤细菌及固氮细菌多样性的影响, 收集和开发固氮菌资源, 筛选高效甘蔗联合固氮体系, 选用3个甘蔗栽培品种‘ROC22’、‘GT21’、‘B8’与大豆品种‘Guizao 2’进行间种栽培, 采用巢式PCR特异扩增细菌16S rRNA基因片段和固氮细菌nifH基因片段, 并结合变性梯度凝胶电泳(DGGE)技术, 对间作大豆的甘蔗根际土壤细菌及固氮细菌进行系统演化和多样性分析。聚类分析结果显示, 间作大豆改变了甘蔗根际土壤细菌及固氮细菌原来的群落组成结构, 尤其对固氮菌群落组成的改变更大, 但对群落物种的优势度影响较小。Shannon-Wiener多样性指数和Simpson多样性指数分析结果表明, 甘蔗-大豆间作显著影响甘蔗根际土壤中细菌和固氮菌的多样性, 其中对固氮细菌多样性的影响较大。不同甘蔗品种的根际土壤细菌和固氮菌在间作大豆条件下表现出不同的多样性, ‘ROC22’和‘GT21’间作处理甘蔗根际土壤固氮细菌的Shannon-Wiener多样性指数显著高于单作处理, 而‘ROC22’与大豆间作处理的甘蔗根际土壤固氮菌多样性最为丰富。在大豆生长盛期, 间作处理的甘蔗根际土壤细菌多样性最为丰富, 不同处理间的差异也最大, 随后下降。总体来看, 甘蔗-大豆间作显著地影响根际土壤细菌和固氮菌的群落结构和群落多样性, 有助于对甘蔗合理间作栽培模式的认识和筛选高效甘蔗联合固氮体系。

Effects of intercropping with soybean on bacterial and nitrogen-fixing bacterial diversity in the rhizosphere of sugarcane

Aims In order to investigate the effects of intercropping with soybean on the diversities of bacteria and nitrogen- fixing bacteria in the rhizosphere of sugarcane (Saccharum officinarum), to collect and exploit nitrogen-fixing bacterial resources, and to screen for efficient sugarcane-associative nitrogen fixation system, an experiment was conducted by cultivating three sugarcane cultivars ‘ROC22’, ‘GT21’, and ‘B8’ with a soybean (Glycine max) cultivar ‘Guizao 2’.
Methods Rhizospheric soil bacteria and nitrogen-fixing bacteria were measured in the rhizosphere of sugarcane intercropped with soybean by using a nested-PCR combined with denaturing gradient gel electrophoresis (DGGE) technique. The specific bacterial 16S rRNA gene fragments and nitrogen-fixing bacteria nifH gene fragments were amplified for phylogenetic and diversity analyses.
Important findings Cluster analysis of bacterial communities showed that the sugarcane-soybean intercropping changed the community composition of rhizospheric soil bacteria and nitrogen-fixing bacteria, with the effect being greater on nitrogen-fixing bacterial communities than on the soil bacterial communities. The intercropping system had a significant effect on the diversity of the rhizospheric bacteria and nitrogen-fixing bacteria; the impact on the diversity of nitrogen-fixing bacteria was greater than on the soil bacteria, and was only minor on the dominance of the bacterial species. Analyses of Shannon-Wiener index and Simpson index showed that the nitrogen-fixing bacteria differed in diversity among the treatments with different sugarcane varieties, and that the sugarcane cultivar ‘ROC22’-soybean intercropping had the greatest diversity. The diversity of soil bacteria in the rhizosphere of sugarcane varied greatly among different stages of crop growth; the booming stage of soybean had the greatest diversity and variations in the diversity among treatments in soil bacteria in the rhizosphere of sugarcane, and thereafter the two variables decreased. In conclusion, the sugarcane-soybean intercropping system had significant effects on the community structures and diversities of soil bacteria and nitrogen-fixing bacteria in the rhizosphere of sugarcane. This is of help for understanding the beneficial effects of sugarcane-soybean intercropping and for identifying efficient sugarcane-associative nitrogen fixation systems.