Screening Of PGPR And Its Physiological Characteristics Of The Curcuma Wenyujin

Curcuma is a traditional Chinese herbal medicine. In recent years, large amount of fertilizer and pesticide has been used, and the Curcuma planting falls into cropping obstacles, resulting in lower yield, medicinal substances reduced, and serious economic losses. Microbial fertilizer has such advantages as low cost, high fertilizer efficiency, saving energy, no pollution, etc. The major promoting plant growth effects of microbial fertilizer are mainly as:transforming nutrients, which is difficult to be absorbed and utilized by plants in nature, into the forms easily absorbed by plants; promoting plant growth and development through the secretion of growth factors; inhibiting the growth of plant pathogens and playing the roles in prevention and control of plant diseases and insect pests by competition, parasitism and other ways. The development and use of microbial agents can reduce the amount of chemical fertilizers and pesticides used, and eliminate Curcuma with obstacles to avoid the drug resistance of curcuma pathogens, while improving economic efficiency and protecting environment.In this study, Curcuma lectin was used as a screening tool to isolate efficient nitrogen-fixing bacteria, phosphate solubilization bacteria and potassium releasing bacteria from Curcuma rhizosphere, and determined the biochemical and physiological activities and siderophores production of these strains.Root of Curcuma was ground, defatted, and extracted by formic acid, and crude Curcuma lectin was obtained by ammonium sulfate fractionation. Crude Curcuma lectin was separated by chitin chromatography, and pure production rate was0.046mg/g. The blood agglutination activity of Curcuma lectin was16, and specific activity was8648.65HU/mg.Forty four rhizosphere bacteria were selected from Curcuma rhizosphere, including13nitrogen-fixing strains,17phosphate solubilization strains and14potassium-releasing strains. There are8nitrogen-fixing strains,10phosphate solubilization strains and8potassium-releasing strains reacting specifically with the Curcuma lectin.Siderophores production of Curcuma rhizosphere bacteria were determinaed using CAS method. Among44Curcuma Rhizosphere strains14strains had siderophore reached the level of "+++++", including4nitrogen-fixing bacteria,6phosphate solubilization bacteria,3potassium-releasing strains. The siderophores productions of strain WEP0500, WEN0101and WEN0102were determinaed by modified CAS method.The results showed that siderophores production of strains WEN0102was still at "5+" level after diluted by four times, siderophores production of strains WEP0500was at "5+" level after diluted by two times, and the datum for strains WEN0101was at "4+" level after diluted by two times. The order of siderophores production of three strains was as the following:WEN0102> WEP0500> WEN0101.The color reaction of Phenanthroline and Fe+was applied to determine the ability of siderophores to combined Fe3+for these three strains. The maximum concentration of Fe3+combined by WEN0102was1985.7μmol/mL, and the data for strain WEP0500and WEN0101were624.0μmol/mL and570.0μmol/mL respectively.Six strains reacting positively with Wenvunjin lectin and having high siderophores concentration were identified. Strains WEK0101and WEP0500were identified as Pseudomonas spp.; WE02and WEP0200as Lactobacillus spp.; WEN0101as Azotobacter spp.; WEK0102as Micrococcus sp. These strains should be further evaluated for their high potential usage as specific bio-fertilizer of Wenyunjin.