Nodulation And Microbial Ecology Of Soybean Endorhizoshere Affected By Inoculated Rhizobial HN01 And Mutant GXHN100

The success of a rhizobial inoculant in the soil depends to a large extent on itscapacity to compete against indigenous strains. With improving inoculantaffection, ecological effection of indigenous microbial communities also needto be attended by rhizobium release to soil. Previous researches show: (1)endorhizosphere microbial communities vary in various plants; (2)endorhizosphere microbial communities vary in seasons; (3) someendorhizosphere microbial communities are not affected by both plant andseason. With the wild type strain HN01 as the control, GXHN100, amutant(S. fredii, strain), was used as soil inoculants for soybean in a field releaseexperiment. The aim of this study is to investigate the differences of nodulationand indigenous microbial community in the root system soil after inoculatingHN01 and GXHN100.Inorder to gain a better understanding dynamics of bacterial communities ofthe endorhizosphere of the soybean, traditional culture-dependent, 16S rDNAgene-based PCR followed by denaturing gradient gel electrophoresis (DGGE), and 16Sr DNA library were used to evaluated the effects of these two strainsinfluence the indigenous microbial community.Nodulation competition test showed that the nodulation occupancy ofGXHN100 was 9.4% while that of the HN01 was 49.4%. Data showed soybeanplants increased the number of microbes. The DGGE patterns suggested that thebacterial communities as determined from direct endorhizosphere DNA extractswere largely stable between inoculanted treatment and noninoculanted treatment.Phylogenetic tree of each 16Sr DNA library showed that the structure ofendorhizosphere microbial community was very similar with each other. In ourstudy, no inoculation-dependent effects could be detected, while the soybeanplants appeared to have a much stronger influence on the microbial community.