Abstract：
Kudzu (Pueraria lobata) is an important medicinal plant, which can associate with rhizobia for nitrogen fixation. The mutualistic symbiosis between rhizobium and kudzu is not well understood, but it is necessary to fully utilize kudzu. Nodules and rhizosphere soils collected from 16 sampling sites were characterized based on phylogenetic analyses of the rpoB gene; 16S rRNA gene; the housekeeping genes SMc00019, truA, and thrA; and the symbiotic genes nodA and nifH. The relationships between biogeographic pattern, nitrogenase activity, and environmental factors were studied. Results indicated that a clear biogeographic pattern of rhizobial communities in the kudzu rhizosphere existed in southern China; latitude and soil pH were found to be the most important factors affecting the biogeographic pattern. Bradyrhizobium diazoefficiens and Bradyrhizobium erythrophlei were the dominant species in kudzu rhizosphere. The symbiotic rhizobia in kudzu nodules mainly belonged to B. lablabi, B. elkanii, B. pachyrhizi, and B. japonicum. Nitrogenase activities in the nodules of kudzu in the Jiangxi sampling region were significantly higher than those in the Guangxi and Hunan sampling regions, and they were significantly negatively correlated to pH and exchangeable Ca. These results constitute the first report of the existence of symbiotic genes in kudzu bradyrhizobia, which are similar to those in B. elkanii and B. pachyrhizi. Our findings could improve the understanding of kudzu-rhizobium symbiosis and could advance the application of rhizobial inoculation in medicinal legumes in terms of increasing the content of active ingredients.
摘要：
葛根是一种重要的药用植物,可以与根瘤菌结合进行固氮。根瘤菌和葛根之间的共生关系还没有得到很好的理解，但是有必要充分利用葛根。根据rpoB基因的系统发育分析，对从16个采样点收集的结节和根际土壤进行了表征；16SrRNA基因；管家基因SMc00019，truA，和thrA；以及共生基因nodA和nifH。生物地理格局之间的关系，固氮酶活性，和环境因素进行了研究。结果表明，中国南方葛根际根瘤菌群落存在明显的生物地理格局；纬度和土壤pH是影响生物地理格局的最重要因素。增氮根瘤菌和红花根瘤菌是葛根的优势种。葛根中的共生根瘤菌主要属于B.lablabi，B.Elkanii,B.pachyrhizi,和日本芽孢杆菌。江西采样区葛根结的固氮酶活性明显高于广西和湖南采样区,它们与pH和可交换Ca呈显著负相关。这些结果构成了关于葛藤属根瘤菌中共生基因存在的第一个报道，类似于B.elkanii和B.pachyrhizi。我们的发现可以提高对葛根-根瘤菌共生的认识，并可以在增加活性成分含量方面推进根瘤菌接种在药用豆科植物中的应用。
