Different Rhizobia In Soil Profile Of Genetic Diversity And Phylogenetic Studies

Rhizobium soil profile distribution and diversity of recovery has important implications for a variety of engineering disturbed soil and soil fertility, but it has not relate to research in this area.For the first time, capturing Rhizobium of 0-300 cm soil profile by legume in agricultural land of Yangling to study rhizobia distribution, genetic diversity and phylogenetic.After planting robinia,On one hand the results show that there is no fixed rules about nodule distribution, revealing nodule distribution has no direct relationship with the distribution of soil nutrients, the reason is not clear at present.It may be related to soil microbial flora or the oxygen content of soil. So it is necessary to study microbial community structure of soil profile further. On the other hand, as the depth increases, soil nitrogen content decreased in 0-120 cm depth, unchanged in 120-150 cm and increased in 150-300 cm. Hydrolysis nitrogen content increased in 0-20 cm, decreased in 20-40 cm and increased in 60-300 cm. Available K content decreased in 0-20 cm, increased in20-300cm; Available P content is decreased generally, except increased in 150-200 cm. organic matter content is an increased trend overall. PH has a little decline trend overall, ranging from 8.5-9 dropped to 8-8.5.50 Rhizobium strains are isolated from the 12 soil profile of 0-300 cm depth totally. 16 S rDNA sequence analysis results show that these strains belong to four Genus, including Mesorhizobium, Sinorhizobium/Ensifer, Rhizobium and Bosea.In 0-5cm Mesorhizobium and Rhizobium is the main, including 65% Rhizobium and 35% Mesorhizobium. In 5-10 cm Mesorhizobium, Rhizobium and Bosea is the main, including 72% Mesorhizobium、18% Rhizobium and 10% Bosea. 10-20 cm is Mesorhizobium and Rhizobium mainly, each 50%. 20-40 cm, 60-80 cm and 80-100 cm mainly is Mesorhizobium. 40-60 cm is mainly Mesorhizobium and Rhizobium, including 65% Rhizobium and 35% Mesorhizobium. 100-120 cm is mainly Sinorhizobium/Ensifer and Rhizobium, 60% and 40% respectively. no isolated rhizobia in 120-150 cm. 150-200 cm is mainly Mesorhizobium, Ensifer and Rhizobium, distribution ratio is the same for a third. 200-250 cm ismainly for Ensifer. 250-300 cm is mainly Mesorhizobium and Rhizobium, 67% and 33% respectively.In addition, the strain 2-7-1 classifies with Bosea vestrisii blong to rhizobia order for the first time, had never found the bacteria in plant root nodules.Nodulation genes nodA sequence analysis results show that nodA of the soil profile is diversity, belonging to three Genus, including Mesorhizobium, Rhizobium and Sinorhizobium. Among them, the rhizobia located in different branches of 16 S rDNA sequence phylogenetic tree is located in the same branch in nodA sequence phylogenetic tree. nodA genes of 12-3 strains at the same big branch with Mesorhizobium, but it belongs to Sinorhizobium/Ensifer in 16 S rDNA phylogenetic tree.Revealing symbiotic genes of the bacteria maybe happenits gene transfer in the potential process of evolution. The nodA genes of 10-1-1 and 10-1-1 Strains classifies with Sinorhizobium, but it belongs to Rhizobium in 16 S rDNA phylogenetic tree.This phenomenon shows that there forms different phylogenetic relationship between gene and 16 S rDNA gene. Nodular gene nodA fragment may be got through horizontal transfer of the symbiotic genes.