Studies On The Isolation And Characterization Of Diazotrophic Endophytesfrom Sugarcane And Their Rhizosphere Soil

In this study, the endophytic nitrogen fixing bacteria and free-living nitrogen-fixing microbes were selected out from sugarcane and its rhizosphere. Nitrogen fixing enzyme activity was measured by acetylene reduction method;According to16 S r RNA gene sequence analysis, the phylogenetic relationships were determined;Using the colorimetric method to measure the auxin, Biolog boardwas used to measure the carbon utilization,The ability of dissolved phosphorus and potassium was measuredby transparent circle method;The culture condition optimization was carried out using live bacteria counting method for the strains with high activity of nitrogen fixation and good physiological and biochemical characteristics; The growth promoting characteristics of rice and maize seedlings were studied by pot cultureon the representative strains of each group.In 35 strains of nitrogen fixing bacteria,The highest activity of g1 was found in 1111.36 nmol/(m L·h). the nitrogen fixing enzyme activity of g7, g6, g116, g98 is higher, more than 500 nmol/(m L · h).The activity of t108 was the lowest, which was 75.37nmol/(m L·h). From the point of view of the activity of the nitrogen fixing enzyme, the superior strains with high efficient nitrogen fixation ability were more.The strains belonged to the Arthrobacter sp.,Bacillus spp., Klebsiella sp., Herbaspirillum sp.,Rouxiella sp., Raoultella sp.,Pantoea sp., Sphingomonas sp., and Kosakoniaspp..The most of the 9 genera were isolated 14 strains from Klebsiella sp.and 8 strains from Bacillus sp.. Among them, the nitrogen fixing enzyme activity of Klebsiella sp. was the highest, and the nitrogen fixing enzyme activity of Bacillus spp. was the lowest.The physiological and biochemical characteristics of nitrogen fixing bacteria were studied. 9 strains of nitrogen fixing bacteria, which had better ability to produce auxin, were obtained, which reached 20.03~384.13 mg/L. Strains b310, t134, g1, g7, g172 with strong ability to dissolve phosphorus.Through the liquid culture of all strains, measured the live bacteria number of t98, g1, g7, g172, g12, g24 was the highest, Optimization of culture conditions with g24, g12, t98 as the representative strains, The number of viable bacteria respectively reached8.8* 109CFU/m L, 6.1*109CFU/m L, 1.25*1010CFU/m L.The effect of nitrogen fixing bacteria on the growth of rice and maize seedlings showed that the 8 representative strains had significant effects on the plant height, dry weight, fresh weight and germination rate of rice and maize.Types of beneficial microorganisms in microbial fertilizer and the number of live bacteria directly affects the quality of fertilizer. This study enriched the germplasm resources of nitrogen fixing bacteria, and provided a good functional strain for microbial fertilizer production.