Studies On The Biological Properties And Symbiotic Nitrogen-Fixing Effects Of Rhizobium Leguminosarum Var. Trifolii In Xining Area

The Trifolium L. is one kind of important herbages.By researching trifolii rhizobium in Xining area ,we found Rhizobium leguminosarum var.trifolii that could fix nitrogen high efficiently and developed the bacterium agent that could be widly used .These finds established a basis for the output's furthrr improving of Trifolium L. in Xining area.This study gathered root nodules from different parts of Xining area and finded nine strains of root nodules and maiden filtered strains of fine characteristics from nine strains which were screened by back inoculation. Three strains were numbered NY6-1,NY6-2,BY5-2.NY6-1 was filtered again by back inoculation which was studied by bacterial agents. Their biological characteristics and symbiotic nitrogen-fixing effects with Leguminosae were preliminarily studied based-on the strains selected as the starting ones.The test showed trifolii rhizobium may have the race singleness, and it coundn't form root nodules on the Glycine max,Medicago sativa, Arachis hypogaea which were not belonged to Trifolium L..After three strains which were filtered again from nine strains were cultivated on the YMA plate for 48h under the condition of 25℃, We found that they would grow into single colonies about 1 - 3mm which were regular round, milk-white or transparent, smooth on the surface, little hunch, smooth on the edge, dope and olefm-like sheening.They never produced vela in liquid culture media and generated a lot of smoke-like sedimentations which disappeared after being shaken after they were cultivated motionlessly for 48h. The result of the violet stain showed that Rhizobium leguminosarum var.trifolii is G^-.The result of flagella staining showed that trifolii rhizobium had only one flagellum growing in one end.The research also demonstrated that it coundn't grow on the beef cream-protease peptone media;it would yield acid after B.T.B reaction;it couldn't liquefy gelatin; it couldn't hydrolyze amylum; it couldn't generate 3-ketone lactose and it did not use citrate.The test of oxygen requirement showed that trifolii rhizobium was a kind of aerobic bacterium; Results of the pH test showed that rifolii rhizobium. growed better under pH from 5 to 8 and beared acidproof basicity.The root nodules is smaller and it's shape like antler or grain. Studying the biological characteristics of Rhizobium leguminosarum var.trifolii shown that it belonged to model of growing fast Rhizobium; NY6-1 was belonged to Rhizobium leguminosarum var. trifolii by test of physiology and biochemistry and correlative literature with NY6-2 and Y5-2.Optimized experiments of medium showed that the optimum constituents for the medium were glucose 15g,NaCl 0.1g, K₂HPO₄ 0.5g, MgSO₄·7H₂O 0.6g, yeast cream 0.4g, CaCl₂ 0.05g, microelement solution for Rh 4ml; when rifolii rhizobium inoculation quantity was 1.5%, temperature as 25℃, pH value as 7.5, and 32h fermentation time operated, the optimal fermentation results could be achieved.The bacterium agent was used potted experiment indicate that all four kinds of bacterium agents made reaches notable difference to Trifolium L. Bacterium agent B (garden soil:plant ash = 7:3) was best to growplant, and bacterium agent A (garden soil: plant ash = 1:0) and bacterium agent D (vermiculite) was secondly.