水稻种子内生泛菌(Pantoea spp.)系统发育多样性及其促生功能

【目的】Pantoea菌株是广泛分布在自然界中的一类功能多样的细菌。本研究对分离自水稻种子内生的Pantoea菌株进行系统发育分析及功能评价,从而确定分类地位、种类多样性、分布特征及功能特性。【方法】采用乙醇-次氯酸钠联合灭菌方法进行水稻种子的表面灭菌,进行内生细菌的分离与纯化;其次将纯化后的菌株进行16Sr RNA基因PCR扩增及序列分析,通过MEGA7软件构建系统发育树;将分离得到的菌株进行功能实验检测,如溶磷、产IAA、产铁载体、拮抗病原真菌等特性,最后检测菌株的溶血性;水稻分型采用SSR方法,并对水稻农学性状如分蘖数、株高、植株重及产量进行调查。【结果】本研究对分离自8个不同基因型水稻种子中的146株内生Pantoea菌株进行系统发育分析及功能评价,结果发现所分离到的泛菌菌株主要属于Pantoea dispersa、Pantoea agglomerans、Pantoea cypripedii以及Pantoea brenneri四个种,其中P. dispersa的菌株数量最多,分布最广,并且存在于所有的8个水稻种子样品中。对其中66株菌进行功能检测,发现86.3%和69.7%的菌株具有溶磷和产IAA能力,有7株菌具有产铁载体能力,未发现对真菌病害Fusarium moniliforme有拮抗作用的菌株,并发现3株菌具有溶血性;本实验未发现泛菌组成与水稻系统发育及农学性状存在明显的相关性。【结论】本研究首次对水稻种子中泛菌的多样性及其功能进行报道,发现不同基因型的水稻种子所含Pantoea种类及组成存在差异,种子选择性地积累了Pantoea类群,大部分菌株具有一定的促生特性。该研究结果有助于进一步探究微生物与植物的共进化、种子微生物的传播途径及作用方式。

Phylogenetic diversity and plant growth-promoting characteristics of endophytic Pantoea spp. in rice seeds

Objective] The genus Pantoea comprises 26 species that are isolated from a multitude of environments. In this study, 146 strains of Pantoea isolated from rice seeds of 8 different rice genotypes were systematically analyzed to determine their phylogenetic status, diversity, distribution and functional characteristics. Methods] First, surface of rice seeds was sterilized by ethanol-sodium hypochlorite, and then the surface sterilized seeds were ground into a powder to isolate endophytic bacteria using the standard dilution plating technique. Second, the strains were purified and 16S rRNA gene sequencing and analyzed. Finally, the isolated strains were tested for plant growth-promoting, such as phosphorus solubilization, indoacetic acid (IAA) and siderophore production, antagonistic and hemolysis. Simple sequence repeats molecular marker technology was used to study the genetic polymorphism in five different genotypes of rice, and some agronomic traits such as tiller numbers, plant height, plant weight and rice production were studied. Results] In total 146 endogenous Pantoea strains were isolated from 8 different genotypes of rice seeds. Pantoea strains were classed to Pantoea dispersa, Pantoea agglomerans, Pantoea cypripedii and Pantoea brenneri based on 16S rRNA gene phylogenetic analysis. Among the 4 species, P. dispersa has the largest size of population and existed in all 8 rice seed samples. Then, 66 strains were selected to test the plant growth-promoting characteristics, 86.3% and 69.7% of the strains were found to have the ability to dissolve phosphorus and produce IAA. 7 strains had the ability to produce siderophore. None of the strains was antagonistic to fungal pathogen Fusarium moniliforme. Another 3 strains had hemolytic activity. Pantoea composition did not correlate with rice phylogeny and agronomic traits. Conclusion] The species and composition of Pantoea were different in different rice seeds. The seeds could selectively accumulated Pantoea as endophytic bacteria, and most of the strains had growth-promoting characteristics.