Isolation Of Endophytic Diazotrophic Bacteria From Gramineae Grasses And Their Activity For Nitrogen Fixation And Plant Growth-Promoting

In this study, the endophytic bacteriaes isolated from the gramineae gras and selected the varieties of functions of Plant Growth-Promoting endophytic bacteria strain with nitrogenase activity, solubilizing phosphate activity, IAA-Producing activity and so on. We study the transmission of field planting and the efficacy of Plant Growth-Promoting of functional strains in the gramineae grass. In order to develop and use the multifunctional microbial inoculant of the gramineae grass, establish the highly effective nitrogenase system of the gramineae grass, promote the growth of the gramineae grasses and strength the optimum ecocycle of grassland to provide the scientific fundament and technical support.The results indicate that the community densities of endophytic bacteria varied depending on different gramineae grass cultivars and tissues in sever Agropyron elongatum(Host)Nevski;Loluim perenne L.;Festuca arundinacea;Elytrigria repens (L.) Desr etc 13 kinds of gramineae grass .The size of population of endophytes in the different cultivars were found to range from 8.70×10~4 to 8.06×10~6CFU/g fresh weight, and were much higer in roots than in foliages. Twenty-one of endophytic diazotrophic bacteria strains were obtained by using CCM medium combined with nitrogen-free selected medium, and the nitrogenase activity is from 8 to 2865 nmolh-1ml-1. It is proved that endophytic bacterial strains with high nitrogenase activity can be isolated from gramineae grass. Determinating the whole 16SrDNA sequence of endophytic diazotrophic bacteria isolated from gramineae grasses and analysising the relationship between the diversity of population and the phylogenesis. The results show that the endophytic diazotrophic bacteria strains isolated from the gramineae grass belong to Agrobacterium, Bacillus, Rhizobium and two independent branches, among them, the Agrobacterium belonging to the dominant population. The diversity index of Shannon is 1.1255; the rich index of Margalef is 0.6569.Tested the all endophytic bacterial strains isolated indicates that 12 strains have solubilizing phosphate activity and its magnitude is 4.18ug/ml-54.64ug/ml;14 strains have the capacity to secrete auxine IAA and the productivity quantum of IAA is 7.01μg/ml-16.55μg/ml; and 8 strains have multi-promoting function including azotification, Solubilizing phosphate and the capacity to secrete auxine IAA, which occupies 38.10% of endophytic diazotrophic bacteria. And the promoted function of the NB42 strain among is predominance.Using the immune electronic microscope dyeing to localization the field planting and transimission of the endophytic diazotrophic bacteria ENB42 in the gramineae grasses, and indicates that the ENB42 strain can invade into the body of host from root and transmit into leaf through conducting tissue. The bacteria ENB42 distributed in the cell space and cell, but the number of bacterias in root colonization is larger than others. Using 15N isotope dilution method to determination the biological nitrogen fixation of ENB42 in the tissues of Festuca arundinacea, Psathyrostachys, Festuca rubra L., the biological nitrogen fixation percentage of 7.366 -28.025%, leaf nitrogen-fixing capacity of 9.834-44.686 kg/hm2, the nitrogen-fixing capacity of the gramineae grasses is more increase than unvaccinated control significantly. The study indicated that the nitrogeny fixation activit was related to the host specificity in a certain degree. Meanwhile there are significant promoting of the grass germination rate, height, weight and other biomass growth traits on inoculation of the strain on the grass. The endophytic diazotrophic bacteria ENB42 strain isolated from the gramineae grass had higher plant Growth-Promoting,better field planting and as a new type of grass for the biological fertilizer have the brighter application prospects.