Jaiswal Sanjay K, Msimbira Levini A, Dakora Felix D
Department of Chemistry, Tshwane University of Technology, Pretoria, South Africa.
Department of Crop Sciences, Tshwane University of Technology, Pretoria, South Africa.
Syst Appl Microbiol. 2017 Jun;40(4):215-226. doi: 10.1016/j.syapm.2017.02.002. Epub 2017 Mar 7.
Groundnut is an economically important N-fixing legume that can contribute about 100-190kgNha to cropping systems. In this study, groundnut-nodulating native rhizobia in South African soils were isolated from root nodules. Genetic analysis of isolates was done using restriction fragment length polymorphism (RFLP)-PCR of the intergenic spacer (IGS) region of 16S-23S rDNA. A total of 26 IGS types were detected with band sizes ranging from 471 to 1415bp. The rhizobial isolates were grouped into five main clusters with Jaccard's similarity coefficient of 0.00-1.00, and 35 restriction types in a UPGMA dendrogram. Partial sequence analysis of the 16S rDNA, IGS of 16S rDNA-23S rDNA, atpD, gyrB, gltA, glnII and symbiotic nifH and nodC genes obtained for representative isolates of each RFLP-cluster showed that these native groundnut-nodulating rhizobia were phylogenetically diverse, thus confirming the extent of promiscuity of this legume. Concatenated gene sequence analysis showed that most isolates did not align with known type strains, and may represent new species from South Africa. This underscored the high genetic variability associated with groundnut Rhizobium and Bradyrhizobium in South African soils, and the possible presence of a reservoir of novel groundnut-nodulating Bradyrhizobium and Rhizobium in the country.
花生是一种具有重要经济价值的固氮豆科植物，可为种植系统贡献约100 - 190千克氮/公顷。在本研究中，从南非土壤中的花生根瘤中分离出结瘤的本地根瘤菌。使用16S - 23S rDNA基因间隔区（IGS）的限制性片段长度多态性（RFLP）-PCR对分离株进行遗传分析。共检测到26种IGS类型，条带大小在471至1415bp之间。根瘤菌分离株被分为五个主要聚类，Jaccard相似系数为0.00 - 1.00，在UPGMA聚类图中有35种限制性类型。对每个RFLP聚类的代表性分离株获得的16S rDNA、16S rDNA - 23S rDNA的IGS、atpD、gyrB、gltA、glnII以及共生nifH和nodC基因进行部分序列分析，结果表明这些本地花生结瘤根瘤菌在系统发育上具有多样性，从而证实了这种豆科植物的混杂程度。串联基因序列分析表明，大多数分离株与已知模式菌株不一致，可能代表来自南非的新物种。这突出了南非土壤中与花生根瘤菌和慢生根瘤菌相关的高遗传变异性，以及该国可能存在新型花生结瘤慢生根瘤菌和根瘤菌的储存库。
