Screening Of Highly Efficient Caragana Rhizobium In Western Inner Mongolia

Three Rhizobium strains isolated from Cagarana in three different drought west area of Inner Mongolia were analyzed for 4 physiological and biochemical characteristics; Three strains were inoculated to the Cagarana using vermiculite and soil in order to screening of effective strain. A strain with strong resistance and obvious growth promoting effect is identified.The results of the phenotypic characteristics showed that:1) The salt-resistant ability of strain 2-S1 was the best, which could be grown on the medium with salt concentration of 2%, and the maximum tolerance to salt concentration of strain 5-9 and DK44 was 1%.2) The acid-alkali-resistant ability of strain 2-Si and 5-9 was best, which could be grown on PH=6.0-10.0 medium; The strain DK44 could be grown on the medium with PH value of 7.0-9.0; The 2-Si strain grow best in culture medium with PH value of 7.0, and strains 5-9 and DK44 growth is best on the medium with PH value of 8.0.3) Among 12 kinds of carbon sources tested, except xylose, succinic acid, sodium citrate and D-fructose, the rest 8 carbon source can be utilized by all of 3 strains; all of strains can not use sodium citrate; Strain of 5-9 can make full use of the seven kinds of carbon source, and its ability that using carbon source was the most widely; The strain 2-Si grow better with four kinds of carbon sources among all kinds of carbon sources tested; The ability of strain DK44 to use the carbon source is worst, and it can only make full use of mannitol and galactose.4) The experiment of only nitrogen source showed all of 11 nitrogen sources can be utilized by 3 strains except the nitrogen sources of (NH4) 2SO4 can not be utilized by the strain of DK44; The ability of all the strains that using organic nitrogen source were better than inorganic nitrogen source; 5-9 strain can make full use of 7 nitrogen sources, and had the strongest ability of utilizing nitrogen source; The strain 2-S1 grow better with four kinds of nitrogen sources; Strain DK44 can only be fully grown with three kinds of nitrogen source, using nitrogen source range is minimal.Pot inoculation test showed that the 3 strains of Rhizobium showed better nodulation ability and different levels effect of promoting plant growth:1) All of the three strains showed obviously nodulation ability, the strain 5-9 nodulation ability is best, more and larger root nodules, nodulation rate was 100%.2) Analysis of growth parameters such as the plant height, root length, aboveground biomass, underground biomass, chlorophyll content and total nitrogen content showed that 5-9 strains showed obvious growth promoting effect on all of growth characteristics to Caragana; The Caragana plant height, root length, the ground and underground biomass can be significantly improve by the strain of 2-Si; The growth characteristics index such as plant height, aboveground biomass and plant total nitrogen content that inoculated strain DK44 is obviously better than control group.3) Linear correlation analysis results show that the growth promoting effect of ground part is better than the underground part by inoculated Caragana Rhizobia; There was a significant positive correlation between the total nitrogen content and fresh weight of root nodules, and the correlation coefficient reached 0.994; The linear correlation coefficient of nodule fresh weight and chlorophyll content is r= 0.711, there is a better positive correlation, which reflects the nitrogen could be promoted assimilate by Rhizobia.The promoting effect of strain 5-9 was the most significant, and it can tolerate the acid and alkali level is PH=6.0-10.0 as well as the more extensive use of carbon and nitrogen sources. Therefore, preliminary screening showed that the strain 5-9 could be used as the test strain in the field experiment.