Effects of comprehensive reclamation of boggy bottomland on soil microbes and yield of soybean in Sanjiang Plain Effect of pH on nodulation of soybean rhizobia from Weifang and Huayuankou soils Effect of Sinorhizobium fredii YC4 symbiotic plasmid amplification on nod factors and symbiotic N-fixation Root colonization and nodulation of Sinorhizobium fredii HN01DL in Glycine max rhizosphere Diversity of Sinorhizobium fredii strains The Construction of Rhizobia Engineering Strain of Introduction a Tandem Gene nodD-lba into Sinorhizobium fredii Root Colonization of Sinorhizobium fredii pSym-Cured Strain HN01 in Rhizosphere of Glycine max