Screening Of Multifunctional Endophytes Of Panax Ginseng And Study On Phosphorus Solubilizing Endophyte GR-69

Panax ginseng C.A.Mey is a perennial medicinal plant in the Aracidae family.Jilin Province,as the main ginseng producing area,has made some contributions to promote the development of ginseng industry.Ginseng contains a variety of ginsenosides,which can reduce blood sugar and enhance immunity.Endophytes isolated from ginseng tissues play an important role in growth and development,formation of secondary metabolites and environmental adaptation,and have a great impact on total yield and quality of ginseng.Ginseng endophytes are isolated from ginseng tissues,which not only have good bacteriostatic effect on ginseng diseases,but also have no adverse effect on ginseng plants.Ginseng endophytic bacteria can improve the resistance of ginseng to the external environment and promote the growth and development of ginseng.The interaction between ginseng endophytes and ginseng plants can also affect the growth and development of the plant itself and its surrounding environment,so ginseng endophytes are favored by ginseng lovers.At present,a large number of studies have shown that most endophytic bacteria of ginseng have a good promoting effect on the growth and development of ginseng plants.In this study,189endophytic bacterial strains and 17 fungal strains were isolated and screened from fresh ginseng root,stem,and leaf tissues from Fusong,Jilin,the main producing area of ginseng.There were23 multifunctional bacterial strains,among which the bacterial strain GR-69 has high phosphorus solubilizing ability.Through morphological,physiological,biochemical,and molecular biological identification,the strain GR-69 was identified as Phyllobacterium myrsinacearum belonging to the genus Phyllobacterium.The fermentation conditions and chemotaxis of the strain GR-69 had been optimized.The study provides a reference for the development of ginseng microbial fertilizer with phosphorus solubilizing effect.The results are as follows:（1）Screening of multifunctional strainsIn this research,through the screening of multifunctional strains detected by different medium plates,8 bacterial strains were screened with the ability to fix nitrogen,5 with the ability to secrete iron carriers,6 with the ability to produce IAA,3 with the ability to dissolve inorganic phosphorus,and 7 with the ability to dissolve organic phosphorus.Strain GS-34 had the ability to fix nitrogen,secrete ferriferous carrier and produce IAA.Strain GR-107 and strain GR-119 had the ability of nitrogen fixation and IAA production.Only GR-69 had the ability to dissolve both inorganic phosphorus and organophosphorus,and the ability to dissolve inorganic phosphorus was strong.The bacterial strain GR-69 showed significant inhibitory effect against three major ginseng diseases（ginseng black spot pathogen,ginseng rust pathogen,ginseng root rot pathogen）.（2）Identification of Panax ginseng endophytic strain GR-69Phosphatase is conducive to the decomposition of insoluble phosphorus by phospholytic strains.In this study,the activities of acid phosphatase and alkaline phosphatase secreted by strain GR-69 were 4.27μg·（m L·h）^-1and 9.43μg·（m L·h）^-1,respectively.In terms of morphology,the colony morphology of the strain GR-69 was milky white and nearly round,with small colonies,smooth and moist surface,opaque colonies,neat edges,and a sense of stickiness.The colonies were micro-uplifted and Gram-negative rod-shaped bacteria.Physiological and biochemical identification results showed that the utilization of potassium nitrate and ammonium sulfate in the utilization of carbon and nitrogen sources were positive.Sucrose,lactose and maltose were all positive,while arabinose,xylose and rhamnose were negative.The contact-enzyme test strain GR-69 showed positive reactions,while the liquefaction of gelatin,starch hydrolysis,methylred and V.P tests,denitrification and phenylalanine deaminase were negative reactions.According to molecular biological identification and analysis,the genome sequence was extracted and input into NCBI for BLAST comparison,and the strain GR-69 was identified as Phyllobacterium myrsinacearum.（3）Optimization of fermentation conditions of Panax ginseng endophytic strain GR-69The optimal carbon and nitrogen sources of strain GR-69 were glucose and ammonium sulfate,respectively,at 35℃,and the phosphorus soluble amount was 298.22 mg·L^-1after 6days of culture.The optimal fermentation conditions were glucose 10g·L^-1,ammonium sulfate0.5g·L^-1and calcium phosphate 12g·L^-1,and the maximum phosphorus soluble content was361.37 mg.L^-1at p H 5.In this study,the phosphorus soluble content of GR-69 strain was the highest when glucose was used as carbon source,and the lowest when soluble starch was used as carbon source.In terms of nitrogen source,when ammonium sulfate is the nitrogen source,the amount of dissolved phosphorus is the highest,and the p H is 5.（4）Chemotaxis response of Panax ginseng endophytic strain GR-69 to ginseng root exudatesThe chemotaxis tropism of Panax ginseng endophytic strain GR-69 was determined by response to a variety of amino acids,saccharides,saponins and phenolic acids.Serine at 0.01mg·L^-1and arabinose at 1.00 mg·L^-1had the greatest influence on the chemotaxis tropism of strain GR-69.The optimum incubation time,temperature and p H were 45 min,25℃and 7,respectively,and the optimum incubation time,temperature and p H were 45 min,25℃and 7respectively.