Screening Of High Efficient Nitrogen Fixation Rhizobium Strains In Desmodium Intortum (Mill.) Urb

Desmodium intortum(Mill.)Urb is a good legume forage and green manure crop,it comes from Central and South America.It has the characteristics of high crude protein content and high yield.It grows fast and tightly.Rooting and flourishing branches and leaves on the ground of stem nodes have good effects on Soil and water conservation and soil improvement.It is widely used in interplanting pasture and orchard.Screening of high efficient nitrogen fixation rhizobium strains in desmodium intortum(Mill.)Urb is an important technology.The inoculation of high efficient Rhizobium is helpful to improve the yield and quality of leguminous forage.At present,desmodium intortum(Mill.)Urb are no efficient strains and bacteria agent of rhizobium in China.In this study,the physical and chemical properties of soil and the content of indigenous rhizobium in the distribution area of leech weed were determined.Therefore,screening of desmodium intortum(Mill.)Urb strains of highly effective nitrogen-fixing rhizobium.On this basis,root nodules with different habitats were collected for isolation,purification and microscopic examination.35 strains of rhizobium were obtained.Preliminary screening by Gram staining.Using 16SrDNA sequencing,add the reference strain,establishing phylogenetic trees,the classification and status of rhizobium of Chinese desmodium intortum(Mill.)Urb were preliminarily determined.In the sand culture condition,by inoculating desmodium intortum(Mill.)Urb,determine plant height,aboveground biomass,underground biomass,nodule number,nitrogen content of cauline leaf,cauline leaf phosphorus content,nitrogen content of the root,the root phosphorus content,nitrogenase activity,and so on.five strains were screened with high efficiency,the specific results are as follows:(1)In different areas of the desmodium intortum(Mill.)Urb,the content of indigenous rhizobium in soil varied greatly,Hainanjianfengling is the highest,to achieve the 1.1×1010,in Hainandanzhou are the lowest,Only 1.5×102.(2)Rhizobia of desmodium intortum(Mill.)Urb in different regions,37 pure cultures were isolated.After purification and microscopic observation,35 strains of rhizobia were obtained.After 16SrDNA sequencing and comparison,there are 35 bradyrhizobium.Comparison on phylogenetic trees,they clustered in six groups with known strains.(3)After planting with sand,the efficient rhizobia obtained were:JF9,JF11,JF18,JF25,LY10,there are five of them.After rhizobia inoculation,above-ground biomass increases respectively:1.59,1.35,1.66,1.16,1.48 times.Nitrogen content of cauline leaf increase:1.14,1.44,1.39,1.13,1.13 times.These are more suitable for desmodium intortum(Mill.)Urb inoculation.It is beneficial to the improvement of yield and quality.