Construction And Highly Effective Recombinant Sinorhizobium Meliloti Strains And Primary Study Of Their Salt Tolerance

A recombinant plasmid pHN307 containing dctABD, nifA and luxAB genes was introduced into Sinorhizobium meliloti HNM1, HNM2, HNM4 and 1021 by tri-parental mating. The stability of pHN307 in the transconjugants under free living conditions was also investigated, the result show that the plasmid exist steadily after cultivated more than 10 generations without any antibiotic. The results of plant pot experiments using cultivar Caoyuan No.l,Gongnong No.1 and Tumu No.2 of Medicago sativa indicated that transconjugant could develop the data of nodule number, nodule fresh weight, shoot fresh and dry weight more or less, so we conclude that the introduction of dctABD and nifA genes could improved the symbiotic nitrogen fixation efficiency of the rhizobia tested.HNM4(pHN307) and 1021(pHN307) could significantly increase shoot fresh and dry weight on Caoyuan No.l and Tumu No.2 comparing with recipient strains. Thus, the effects on the symbiotic nitrogen fixation of Sinorhizobium meliloti with the introduction of dctABD and nifA genes are also relevant with Medicago Sativa variety. On the Caoyuan No.1 and Gongnong No.1, the inoculation of transconjugant could develop shoot fresh and dry weight comparing with wild type, but on the Tumu No.2, the inoculation of HNM4(pHN307), 1021(pHN307) could not improved the shoot fresh and dry weight significantly, and HNMl(pHN307) demonstrated negative effect under the same condition.We also study the salt tolerance of transconjugants and Medicago Sativa plant. The result demonstrated that 2.5% NaCl concentration could inhibit growth of strains tested significantly, and the plants tested could not grow and form nodule under the environment of 1.5% NaCl concentration.