Study On Isolation,Identification And Biological Characteristics Of Astragalus Membranaceus Root Rot Pathogeny

One fungi strain was isolated from the root of Astragalus membranaceus by using the conventional method from the four-year old root of Astragalus membranaceus.The result was showed as followed:the strain was identified with morphological and 18srDNA sequences of ITS identification methods,the pathogen was ensured that the strain is the root rot pathogen to lead Astragalus membranaceus root disease.So the biological characteristics were study comprehensively.The research results as followed:1.The Fusarium oxysporum was identified by morphological and 18SrDNA ITS sequence as fungi,deuteromycetes,Fusarium and Fusarium oxysporum.2.The pathogen optimum growth temperature is 25? the pathogen is extremely sensitive to temperature,the optimal temperature higher or lower than the growth rate will be significantly weakened.3.The pathogen have a wide range of pH adaptability,within the scope of the pH 4.0?10.0,all can grow well,under acid condition can be obtained as the rise of the pH and rapid growth,under the condition of high alkaline,showed strong growth quantity tolerance and accumulation of biomass.4.Fusarium oxysporum are hooked on the organic nitrogen,and to the use of complex organic nitrogen ability than simple organic nitrogen source,organic nitrogen in yeast extract,for the best,does not contain benzene class of amino acid nitrogen source also has a good ability to absorb and make use of.Peptone,D-phenylalanine,L-phenylalanine,ammonium dihydrochloride,ammonium chloride,ammonium sulfate are adverse to the growth of the pathogen.In the environment of fertilization with ammonium sulfate as nitrogen fertilizer,the disease caused by the disease has a certain control on the rapid spread of disease.5.Glucose is the pathogen of cellulose and the optimum carbon source,because the soil contains a lot of cellulose,which is led to the pathogen is a major cause of soil diseases,statistics show that the ability of the pathogen in the use of cellulose to glucose have no significant difference,show that the pathogenic bacteria secrete extracellular cellulose ability is very strong.6.The spore germination of pathogenic bacteria was positively correlated with the optimum nitrogen source,carbon source and pH,show strong consistency;it is negatively correlated with the generation time of conidium,improper environmental conditions can shorten the reproducing time of conidium,thus the time of influence will be shorten by the condium generation.