不同连作年限野生地黄根际土壤微生物群落多样性分析

以野生地黄为试验材料,设置野生地黄头茬土壤、重茬土壤和原茬土壤处理,未种植任何作物为对照,于块根膨大中期采集土样,通过磷脂脂肪酸法(PLFA)和末端限制性片段长度多态性(T-RFLP)技术,分析不同连作年限野生地黄的根际微生物生物量和群落结构变化。PLFA分析结果表明,不同处理情况下地黄根际土壤微生物群落结构存在明显差异,与头茬地黄根际土壤相比,重茬地黄土壤微生物总量显著下降,并且细菌/真菌比例下降。T-RFLP分析结果表明,不同连作年限地黄根际土壤细菌群落结构存在一定差异,野生状态地黄土壤和头茬土壤菌群较为相似,变形菌门和厚壁菌门占据优势地位。野生状态地黄和头茬地黄根际富含Bacillus、Pseudomonas等有益生防菌,而重茬地黄根际土壤滋生大量病原菌如Clostridium sp.、Flexibacter polymorphus和Clostridium ghoni,有益菌群和纤维素降解菌群减少,q RT-PCR定量分析也显示,野生状态地黄和头茬地黄土壤中假单胞菌数量都显著高于重茬地黄土壤。总之,野生地黄存在连作障碍问题,导致野生地黄根际有益菌数量减少而病原菌大量滋生,从而降低了野生地黄抵御病害的能力,使重茬野生地黄生长发育差,产量大幅降低。

Diversity Analysis of Rhizosphere Microflora of Wild R. glutinosa Grown in Monocropping for Different Years

The soils sampled from the four different plots, including the newly planted, the two-year monocultured, the wild R. glutinosa and the control without growing R. glutinosa, were used to study the changes in microbial biomass and community composition using phospholipid fatty acid (PLFA) and terminal restriction fragment length polymorphism (T-RFLP) analyses. PLFA analysis indicated that the soil microbial community composition was significantly different among the R. glutinosa with different years of monoculture. Compared with the newly planted soil, the total PLFA content and the ratio of bacteria/fungus in two-year monocultured soil greatly declined. Further analysis by T-RFLP also displayed the distinct differences in rhizospheric bacterial community structure of R. glutinosa. The microbial compositions from the wild and the newly planted R. glutinosa soils tended to be more similar. It was found that the bacteria including Proteobacteria and Firmicutes were predominant in the wild and newly planted R. glutinosa soils. Some beneficial biocontrol bacteria (such as Bacillus, Pseudomonas, etc.) gathered in the rhizosphere of the wild and newly planted R. glutinosa. However, a large number of pathogenic bacteria bred in the rhizosphere of the two-year monocultured R. glutinosa, such as Clostridium sp., Flexibacter polymorphus and Clostridium ghoni, and the number of beneficial bacteria and cellulose degradation bacteria decreased. Furthermore, qRT-PCR analysis verified that the total number of Pseudomonas was much higher in the wild and newly planted R. glutinosa soils than in the two-year monocultured soil. In conclusion, the pathogenic microbes breed seriously in the rhizospheric soil of wild R. glutinosa under the monoculture regime, and yet the number of beneficial bacteria decline, resulting in weakened ability of wild R. glutinosa to resist the diseases so that the two-year monocultured wild R. glutinosa grows abnormally and its yield is decreased drastically.