The Responses Of Two Soybean Rhizobium To Uniconazole And Its Preliminary Application

Rhizobium is the symbiotic nitrogen-fixing bacterium of soybean,how to promote the proliferation of Rhizobium and increase the nitrogen fixation of soybean nodules is a key in soybean production.Plant growth regulators have been widely used in soybean production in recent years,it has become indispensable to find out that Rhizobium respond to plant growth regulators and the application of Rhizobium interact with plant growth regulators.Taking strains of Sinorhizobium fredii and Bradyrhizobium elkanii as the research materials,the concentration of uniconazole from 0.001 mg·L-1 to 100 mg·L-1 were used to culture those two strains.Rhizobium growth was measured by plate colony counting and liquid culture,the cell morphology was observed by scanning electron microscopy,with these two methods to investigate the effect of uniconazole on Rhizobium growth.The Rhizobium transcriptomes was analysed to investigate the response of rhizobia gene and metabolic pathway to uniconazole.Soybean seed was presoaked by Uniconazole with 1 mg·L-1,30 m L Rhizobium liquid in logarithmic growth phase was mixed with soil per 2.5 kg,the ureide content in root and nodule nitrogenase activity were assayed in flowering-poding phase to reflect the effects of those two strains and Uniconazole interaction to symbiotic nitrogen fixation.The enzyme activities of SOD,POD and CAT,the MDA level in soybean leaf and root were assayed in flowering-poding phase.Soil urease,catalase and phosphatase activities in soybean seedling,three-leaf stage,four-leaf stage,early flowering stage and podding stage were tested.Based on these two methods,the effect of Rhizobium and Uniconazole interaction on the growth of soybean was determined.The results showed that the amount of S.fredii and B.elkanii was inhibited when the concentration of Uniconazole was higher than 10 mg·L-1,but the amount of these two strains was promoted when the concentration of Uniconazole was 1 mg·L-1,the amount of S.fredii and B.elkanii was increased 20%~40%,the width of B.elkanii cells cultured at the concentration of 1mg·L-1 uniconazole was increased.Transcriptome analysis showed that fix gene,fli gene and atp gene were up-regulated.In cell metabolism pathways,peptide biosynthetic process,peptide metabolic process,cellular amide metabolic process,cellular protein metabolic process,organonitrogen compound biosynthetic process and organonitrogen compound metabolic process were up-regulated.In the aspect of soybean nitrogen fixation,Rhizobium and Uniconazoleinteraction were effectively increased soybean nodule nitrogenase activity,at the same time,the ureide content in soybean root were increased 5%~8.4%.In soybean growth,Rhizobium and Uniconazole interaction were effectively reduced the MDA level about 40%~60% in soybean roots and leaves,but the three enzyme activities were not significantly affected.Rhizobium and Uniconazole interaction were effectively increased the catalase activity in soil over the five periods,however,the changes of urease and phosphatase activities in soil were not significant.This experiment confirmed the Uniconazole could promote the growth of Rhizobium,up-regulate the growth metabolism genes of Rhizobium.Rhizobium and uniconazole interaction can increase nitrogen fixation of soybean nodules,reduced MDA content in soybean and improved catalase activity in soil.The results provided the theoretical basis and technical support for the application of new technologies in soybean cultivation.