Biological Characteristics, Physiological And Biochemical Effect Of The Pathogenic Bacterium On Sweet Osmanthus Leaf Blight

The research identified the pathogenic bacterium of sweet osmanthus Leaf Blight,studied its biological characteristics and the effects on physiological and biochemical characteristics of sweet osmanthus leaves,to understand the disease and provide theory evidences to prevent the disease.The reaults as follows:After observing the morphologic characteristics of the pathogenic bacterium grow on PCA medium which is poor nutrition,identified that the pathogenic bacterium of sweet osmanthus Leaf Blight is Alternaria tenuissima(Ft.) Wiltshire.The results indicated that the suitable medium was PDBA for mycelia growth,while OLA for sporulation.The best carbon source was starch-sugar for mycelia growth and nucite for sporulation.The best nitrogen source was peptone for mycelia growth and sporulation,while ammonium salt would inhibit the mycelia growth and sporulation.Lack of Mg,S,P was disadvantage for mycelia growth,while lack of K was disadvantage for sporulation.Adding Zn and Ve was advantage for the growth of mycelia,while Cu and Vb₂ was benefit for sporulation.The ranges of temperature and pH which effect mycelia's growth were 20-30℃and pH5-10,the optimum were 25℃and pH6,the conditions of sporulation were 15℃and 30℃and pH6-11,the optimum were 30℃and pH7.The continue darkness giving received better results for mycelia growth and sporulation than others.The germination was stimulated by adding of leaf juice of sweet osmanthus,sucrose,glucose and beef extract.The ranges of temperature,pH and RH for conidial germination were 23-30℃,pH 3-7 and 98%-100%,the optimum were 27℃,pH6 and 98%;and the fungus were killed at 55℃,10 min.The effects ofAiternaria tenuissima on the photosynthetic pigment,tissue permeability,MDA content, CAT,POD and SOD activities of sweet osmanthus leaves showed that A.tenuissima discreased the pigment contents,increased the tissue permeability and the MDA contents and membrane lipid overoxidation.And CAT,POD activities in sweet osmanthus leaves were lower than the CK.But SOD activity was higher than the CK at first,then became lower than the CK.The research provided theoretic basis on sweet osmanthus.Applied ammonium nitrogen,or use NH₄Cl,(NH₄)₂SO₄ to increase the effects of chemistry medicament and bio-pesticide to prevention and cure sweet osmanthus Leaf Blight,added phosphorus,pruning and drain,keep aeration,air-dry condition can reduce occur of sweet osmanthus Leaf Blight.