Study On Genetic Diversity And Phylogeny Of Soybean Bradyrhizobia And Cowpea Rhizobia From Crop Zones Of China

Genetic diversity and phylogeny of 44 indigenous strains of Bradyrhizobium from soybean (Glycine max L.) cropping zones of China were investigated through 16S rRNA PCR RFLP, 16S rRNA sequencing, 16S-23S rRNA PCR-RFLP and G-C rich RAPD assays. Results of 16S rRNA PCR-RFLP and sequence analysis shown that strains tested and reference strains were clustered into 4 genotype, Genotype I consisted of 18 isolated strains mainly from the north of China.,which appeared genetic differences from B. japnicum, B. liaoningense and B. elkanii. Genotype II comprised 23 isolated strains, all reference strains but USDA6 of B. japonicum, and the type strains of B. liaoningense. Genotype III solely consisted of type strains of B. japonicum USDA6 Genotype IV comprised three isolated strains and the reference strains of B. elkanii.l6S rRNA sequences shown that HAS5 clustered with the reference strains of B. elkanii, and the sequence divergence between HAS5 and USDA76 was 0.4%. Strains of DD3, BQ3, GXD1, JZ2, and reference strains from other species formed a large homological cluster sharing a high homology in 16S rRNA sequence, and their sequence divergence was less than 1%.Results of 16-23S rRNA PCR-RFLP shown that group I comprised the same strains of Genotype I in 16S rRNA RFLP assay. Strains of Genotype II in 16S rRNA RFLP assay were divided into group II and group III. Group II contained B. liaoningense and partial isolates from Genotype II. Group III consisted of B. japnonicum and the remains of genotype II, and mainly isolated strains from central China Yangtze River drainage basin .Group IV consisted of three strains from Hongan and B. elkanii.Results of RAPD analysis shown that test strains and reference strains were also divided into I , II, III,IVgroups in the similarity of 72%.They are similiarily tol6-23S rRNA PCR-RFLP assays. At higher similarity, strains tested from different area were further clustered which reflected the effect of geographical factor on rhizobia genetic diversity.16S rRNA RFLP, 16S rRNA sequencing, 16S-23S rRNA Intergenetic Spacer (IGS) RFLP and G-C rich RAPD assays were conducted to clarify genetic diversity and phylogeny of 55 indigenous cowpea [Vigna unguiculata (L.) Walp.] rhizobia from different geographic regions of China. Isolated cowpea rhizobia comprised six 16S rRNA genespecies. Genotype I consists of 15 isolated strains from different geographic region. Together with reference strains of B. japonicum and B. liaoningense, they share the same RFLP patterns. Genotype II comprises 26 isolated strains, which was genetically separate from B. japnicum, B. liaoningense, and B. elkanii. GenotypeIII contains 7 isolates and the reference strains of B. elkanii. Genotype IVwas solely consisted of strain DdE4,...