旱直播条件下强弱化感潜力水稻根际微生物的群落结构

Analysis of rhizosphere microbial community structure of weak and strong allelopathic rice varieties under dry paddy field

运用末端限制性片段长度多态性(T-RFLP)技术,以强化感水稻品种PI312777和弱化感水稻品种Lemont为材料,研究了旱直播模式下5叶期和7叶期化感水稻根际土壤微生物的组成和结构。结果显示:HaeⅢ和MspⅠ2种内切酶分别检测到9—87个TRFs、15—89个TRFs,各个样本的TRFs排序间存在极显著差异,表明各样本的微生物的相对丰富度存在极显著差异。用物种丰富度(S)、香隆指数(H)、Simpson多样性指数(D)、均匀度指数(E)评价了6个样本中TRFs的多样性,香隆指数最能体现2个酶切片断中TRFs的多样性,PI7中TRFs多样性最高。聚类分析和主成分分析表明旱作条件下强弱化感潜力水稻在生育前期(5叶期以前)根际微生物群落的组成与结构相似性较大,而7叶期强弱化感水稻及对照之间微生物群落差异较大,表明水稻根际微生物的组成既受生育期的影响又受水稻品种的影响。7叶期的化感水稻根际微生物呈现最大物种丰富度和香隆-威尔指数多样性,在其特有的34个菌中有7个属于粘细菌目,另外还有一些滑行菌和一些与氮循环相关的细菌等。粘细菌可能通过次生代谢产物抑制伴生杂草种子的萌发,降低杂草的密度从而提高化感水稻的化感作用潜力。

Terminal restrain fragment length polymorphism（T-RFLP） technique was employed to investigate the microbial community structure and composition in the rhizosphere of weak and strong allelopathic rice varieties directly sowing on dry paddy field at 5-leaf stage and 7-leaf stage.The results showed that 9—87 TRFs and 15—89 TRFs were detected from the soil DNA digested with two restriction enzymes Hae Ⅲ and MspⅠ,respectively.The rank-abundance of TRFs from different samples showed extremely significant difference,indicating that relative abundance of rhizosphere bacteria was markedly different.The diversity indices including species abundance（S）,Shannon-wiener diversity index（H）,Pilow diversity index（D） and evenness index（E） were used to analyse the diversity of TRFs in 6 samples.The analysis of correlation coefficients among species indices showed that Shannon-wiener diversity index was the best one for the invesitigation of the species diversity.The Shannon-wiener diversity in the sample of PI7 was the highest compared with those in the others.The cluster analysis and principle analysis suggested the similarity among the 3 samples of 5-leaf stage was greater than that of 7-leaf stage.Especially,the three samples of 7-leaf stage were separated by not only principal component Ⅰbut also principal component Ⅱ,which implicated that the composition and structure of soil microorganism community could be regulated by both growth stage of rice and rice variety.The Shannon-wiener diversity index and species richness of PI7 were the highest in all samples,and 34 genera were special in PI7,in which 7 genera belonged to myxobacteria.Some sliding bacteria and N-fixing bacteria were also found in those special genera of PI7.Secondary metabolites of Myxobacteria might improve the allelopathic potential of allelopathic rice by inhibiting germination of weed seeds in soil seed bank and decreasing the density of weeds in the field of rice.