I-rhizobia Genetic Transformation And Its Application Ii Of Dna Supercoiling Regulation Of Nif Gene Expression

We have constructed two recombinant Rhizobium strains Sinorhizobium fredii LMG101 and Rhizobium leguminosarum LMG301 both of which carrying an extra copy and constitutively expressed nifA gene and then we tested their symbiotic efficiency of nodulation and the ability of nitrogen-fixation under laboratory or agricultural conditions. The plant in field inoculated with the recombinant strain shows enhancement of the efficiency of nodulation and the ability of nitrogen-fixation comparing the plant inoculated with the wild type. In XinJiang and JiangSu province the recombinant strain LMG101 increases soybean yield in field by 10% comparing the field inoculated with the control and 5% comparing the field inoculated with the wild type. In the field which has not been planted legumes before the recombinant strain increases soybean yield by 42% comparing with the control. The plant inoculated with the recombinant strain Rhizobium leguminosarum LMG301 shows enhancement of the efficiency of nodulation and the ability of nitrogen-fixation comparing the plant inoculated with the wild type under laboratory and field conditions. Inoculation with the recombinant strain LMG301 made the plant weight and the number of nodules increase 40% and 140% respectively comparing the inoculation with wild type under laboratory condition. Furthermore the recombinant strain Sinorhizobium fredii LMG102 which carrying a constitutively expressed S.meliloti nodD3 increases the plant biomass, the number of nodules and the nitrogenase activity of the nodules under controlled conditions comparing with the wild type.