水稻种子的细菌含量和群落结构及其影响因素分析

【目的】种子是植物微生物群代际传递的重要途径,但种子携带的微生物群落尚缺乏系统的研究。本研究以水稻种子为模型,定量分析种子的细菌含量、测定种子的细菌群落结构、探究地域与品种对细菌含量及群落结构的影响和鉴定水稻种子的核心菌群。【方法】选取18个水稻品种,每个品种分别来自中国海南和天津2个地域,共36组样本。每组样本包含5或10个DNA样本,每个DNA样本由3粒种子提取的总DNA构成。使用细菌特异性16S rDNA介导的荧光定量PCR技术测定种子的细菌含量,并分析影响因素;使用16S rDNA扩增子测序技术测定种子的细菌群落结构,并用生物信息学方法分析了影响因素和核心菌群。【结果】本研究测定了1 080粒水稻种子的细菌含量,发现经过表面除菌的水稻种子内部存在共栖细菌,平均每克种子的细菌含量为1.53×10⁶。水稻品种对种子的细菌含量有显著影响,而地域无影响。测定180个扩增子文库的细菌群落结构,发现水稻种子的菌群与水稻植株有相似之处,均以变形菌门为主要的细菌门类;地域对水稻种子的细菌群落结构有重要影响,不同地域的水稻种子在主坐标分析(principal co-ordinate analysis, PCoA)中有明显分离;而粳稻和籼稻之间无显著差异。还发现水稻种子存在核心菌群,且相对丰度高达总菌群的85.56%。【结论】本研究系统地揭示了水稻种子的细菌含量、群落结构及其影响因素,为利用种传微生物促进水稻健康提供了数据和方法支持。

Bacterial abundance and community structure in rice seeds and their influencing factors

[Objective] Seeds are an important pathway for the intergenerational transmission of plant microbiota, while the systematic research on the microbiota carried by seeds remains to be carried out. In this study, we measured the bacterial abundance, determined the bacterial community structure, explored the effects of planting regions and rice cultivars on bacterial abundance and community structure, and identified the core bacterial taxa in rice seeds. [Methods] We collected 36 groups of samples of 18 rice cultivars, each from Hainan and Tianjin in China. Each group of samples contained 5 or 10 DNA samples, each of which was extracted from 3 seeds. The fluorescent quantitative PCR for bacterial 16S rDNA was employed to measure the bacterial abundance in seeds, and the factors influencing the abundance were explored. The 16S rDNA amplicon sequencing was performed to determine the bacterial community structure in seeds. Furthermore, bioinformatics tools were used to analyze the factors influencing bacterial community structure and the core bacterial taxa. [Results] We measured the bacterial abundance of 1 080 rice seeds and found that endophytic bacteria existed in the rice seeds after surface sterilization, with the average abundance of 1.53×10⁶ per gram of seeds. The bacterial abundance in seeds was affected by rice cultivars rather than planting regions. We measured the bacterial community structure of 180 amplicon libraries and found that the bacterial community in rice seeds was similar to that in rice plants, both dominated by Proteobacteria. Planting regions significantly affected the bacterial community structure in rice seeds. The rice seeds from different planting regions were clearly separated in principal co-ordinate analysis, while there was no significant difference between japonica and indica. In addition, rice seeds had core bacterial taxa, with the relative abundance up to 85.56%. [Conclusion] This study systematically revealed the bacterial abundance and community structure in rice seeds and their influencing factors, providing data and methods for using seed-borne microorganisms to improve rice health.