| Chemical fertilizer bring up huge income to agriculture production while resulting in serious environment pollution.The research of separating excellent PGPR(plant growth-promoting rhizobacteria,named PGPR)strains from plant rhizophere will alleviate the environment crisis that chemical fertilizer bring up,and providing theoretical basis to promote plant growth.But there is recession phenomenon exsit in PGPR using in actual production.Thus screening PGPR strains is a dynamic continuous process.Research object in this paper is excellent PGPR that separate from Leymus chinensis and Puccinellia tenuiflora.We screen 9 srains through determinig its physicochemical properties and growth promoting characteristics,and analysising these16 SrDNA.Finally we identify 4 strains.Key findings are based on followings:1.Using Assby and PKO selective medium,respectively separate 106 strains from Leymus chinensis and Puccinellia tenuiflora rhizosphere,including azotobacter bacteria79 strains,separating 50 strains azotobacter bacteria from Leymus chinensis,29 strains phosphorus bacteria from Puccinellia tenuiflora;the other 27 strains separated from Puccinellia tenuiflora,separating 20 strains from Leymus chinensis,7 remained separated from Puccinellia tenuiflora.The distribution of azotobacter and phosphorus bacteria in Leymus chinensis and Puccinellia tenuiflora show trend that RS>NRS>RP>HP.2.We determined the nitrogenase activity of nitrogen fixing bacteria,and testing phosphate solubilizing ability of phosphate solubilizing bacteria,PH of culture medium,the ability of two strains to secrete IAA and salt tolerance.In terms of nitrogen fixation capacity,YCN-3 has the strongest Nitrogenase activity,to 200.64 nmol C2H4·m L-1,Compared with other strains,being significant difference.In the aspect of dissolving phosphorus,Compared with blank and other strains,the phosphate solubilizing ability of strains YCP-19 enhance significantly.In terms of secreting IAA,YCN-2,XXP-21 respectivily arrive at 31.24 μg/m L 和 27.60 μg/m L,Compared with blank,the secreting IAA of this two strains surpass blank significantly,and secreting ability surpass other strains significantly.In the aspect of salt tolerance,YCN-3 and YCP-19 is better.3.Effect of 9 excellent strains on growth of Leymus chinensis Promoting thegrowth of Leymus chinensis roots,YCN-3 compared with the control group,Root length increased by 22.71%.The growth promoting effect of host plant was obvious.Promoting the growth of Leymus chinensis,YCN-5 had the best effect on the growth of host plant,12.74% higher than the control group.Promoting the growth of dry weight of Leymus chinensis,The effect of XXP-21 on the dry weight per plant of non host plant is best.Compared with the control group increased by 28.57%,YCN-3effecting on the aboveground dry weight per plant is best,Compared with the control group increased by 21.73%;every strain effecting on underground dry weight is not signifant.In terms of Leymus chinensis P content: YCP-25 effecting on the P to host plant is best,surpassing 26% compared with the control group,XXP-21 effecting on the underground P to host plant is best,,surpassing 16.25% compared with the control group.4.Carring out 16 SrDNA analysis of 9 strains isolated from PGPR,Finally,4 strains of YCN-5 and XXN-11 were identified as Bacillus,YCN-2 and XXP-21 belong to the Sphingomonas... |
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