红花檵木异常叶色现象与叶片内生细菌的相关性

Correlation between abnormal leaf color phenomenon and endophytic bacteria of Loropetalum chinense var. rubrum

关键词:  红花檵木,异常叶色,内生细菌,细菌多样性,群落结构

Key words:  Loropetalum chinense var. rubrum, abnormal leaf color, endophytic bacteria, bacterial diversity, community structure

摘要:

为探讨红花檵木叶片内生细菌与其季节性异常叶色现象的相关性,该文采用平板分离培养法和16S rDNA序列特征分析法从红花檵木5类异常叶色和正常红色叶片中分离鉴定内生细菌,分析不同叶色叶片的细菌多样性、群落结构和功能菌水平差异。结果表明:(1)5类异常叶色叶片内生细菌生物量较高,分离的906株细菌经鉴定为26属40种。(2)小叶类型叶片内生细菌种类最多且群落结构均匀,而红黄类型的结果与其相反。(3)异常叶色叶片与正常红色叶片的菌群比较发现,不但其优势属、种差异明显,而且在异常叶色叶片中富集大量甲基杆菌属和假单胞杆菌属细菌,尤其是栖稻假单胞菌明显增多。(4)异常叶色叶片(小叶、红斑和红黄类型)中富集了具有溶磷、固氮、产IAA、耐盐功能的细菌,其中有4株兼具以上4种功能,由此推断这种富集功能菌的行为极有可能与异常叶色现象有关。该文揭示了红花檵木异常叶色现象与特定内生细菌菌群富集密切相关,为红花檵木异常叶色的形成机理研究提供了线索,对红花檵木优质高效栽培具有重要应用价值。

Abstract:

In this study, in order to to investigate the correlation between endophytic bacteria in the leaves of Loropetalum chinense var. rubrum and the seasonal abnormal leaf coloration phenomenon of this plant, we performed plate isolation and culturing and subsequent 16S rDNA sequence analysis to isolate and identify endophytic bacteria from five types of abnormally colored leaves and normally red-colored leaves of L. chinense var. rubrum; we also analyzed differences in bacterial diversity, community structure, and functional levels among differently colored leaves. The results were as follows:(1)Compared with the normally red-colored leaves, we detected higher biomass of endophytic bacteria in the five types of abnormally colored leaves. Among the isolated bacteria, 16S rDNA sequence alignment and phylo-genetic tree analysis revealed that the presence of 906 bacterial strains were classified into 26 genera and 40 species.(2)While the smaller leaves were colonized by the largest number of endophytic bacterial species with a relatively uniform community structure, the opposite was true for bacteria isolated from the red- and yellow-pigmented leaves.(3)Comparison of the bacterial community data for abnormally colored leaves and those with the normally red-color revealed that not only were there significant differences with respect to the dominant genera and species, but also an enrichment of numerous bacterial species in the genera Methylobacterium and Pseudomonas in the five types of abnormally colored leaves. Particularly, we detected significantly larger numbers of Pseudomonas oryzihabitans.(4)We established that abnormally colored leaves(smaller, red spotted, and the red and yellow types)were characterized by an enrichment of bacteria with phosphorus solubilization, nitrogen fixation, IAA production, and salt tolerance functions, among which, four strains were found to have all four of these functions. Accordingly, we speculate that the abnormal leaf coloration of L. chinense var. rubrum is closely associated with the activities of these enriched functional bacteria. Our findings in this study indicate that the abnormal leaf coloration of L. chinense var. rubrum is closely associated with the enrichment of specific endophytic bacterial communities, which can thus provide clues for elucidating the mechanisms underlying the development of abnormal leaf color in this plant. Moreover, this may have important application value for the efficient cultivation of high-quality L. chinense var. rubrum.