Abstract: To explore the effect of Pantoea agglomerans CQ10 Lipopolysaccharide (CQ10-LPSp) on the endophytic bacterial diversity and its Rhizobium. The experiment firstly ground and separated the bacteria of ‘Ju neng 551’ alfalfa seeds, and then sets 6 different concentrations (0, 0.133 5, 0.200 3, 0.267 0, 0.333 8, 0.400 5 EU·mL^-1) of CQ10-LPSp were interacted with alfalfa and associated bacteria, next the endophytic bacteria and Rhizobium in the root system were separated. The results showed that, with the increase of the concentration of CQ10-LPSp, the number of Rhizobium in alfalfa first increased and then decreased. The number of Rhizobium was the highest at 0.267 0 EU·mL^-1 CQ10-LPSp, which was 6.98×10⁷ cfu·g^-1. At this concentration, the species of endophytic bacteria was less diverse than the species-carrying bacteria in the root system. The results showed that, CQ10-LPSp affects the types and number of endophytic bacteria in plants. Within a certain concentration range, it can promote the number of endophytic Rhizobium in alfalfa. The results of the study lay a certain theoretical and practical foundation for the development of exogenous additives that promote the growth of alfalfa endophytic Rhizobium.

Key words: Lipopolysaccharide, Alfalfa, Bacteria diversity, Rhizobium

摘要： 为了探究成团泛菌CQ10脂多糖（Pantoea agglomerans CQ10 Lipopolysaccharide，CQ10-LPSp）对紫花苜蓿（Medicago sativa L.）幼苗内生细菌多样性及其根瘤菌（Rhizobium）的影响，本试验首先研磨分离‘巨能551’紫花苜蓿幼苗内生细菌，后设置6个不同浓度梯度（0，0.133 5，0.200 3，0.267 0，0.333 8，0.400 5 EU·mL^-1）的CQ10-LPSp与紫花苜蓿互作，再分离并测定了其根系内生细菌的种类和数量以及根瘤菌的数量。结果显示，随着CQ10-LPSp浓度的增大，紫花苜蓿内生根瘤菌的数量呈先升高后降低的变化趋势，在0.267 0 EU·mL^-1 CQ10-LPSp下根瘤菌数量最多，为6.98×10⁷ cfu·g^-1，且该浓度下根系内生细菌种类较种带细菌多样性减少。结果表明，CQ10-LPSp处理下会影响植物内生细菌的种类和数量，且在一定浓度范围内能增加紫花苜蓿内生根瘤菌的数量。本研究结果为开发促进紫花苜蓿内生根瘤菌生长的外源添加剂奠定一定的理论和实践基础。

关键词: 脂多糖, 紫花苜蓿, 细菌多样性, 根瘤菌