Studies On The Biological Characteristics And Toxin Of Colletotrichum Gloeosporiodes On Osmanthus Fragrans In Kaifeng Area

Anthracnose is one of the most serious leaf diseases of Osmanthus fragrans.It can cause the leaves' kraurosis and separation even led to the death of the host tree when occurs badly,so it has a pernicious influence on the economic value and ornamental value of Osmantus fragrans.This experiment researched into the identification of the anthracnose pathogen,biological characteristics,the extraction and mechanism of action of the morbigenous toxin .It's deliberately calculated to definite the species of the pathogen and its biological characteristics more extactly,screen out the fungicide that could inhibit the pathogen fungus effectively and know its pathogenic machinism ,increase the knowledge of the disease and provide a certain degree basis on the preventing and controlling of the anthracnose. The main conclusions of this study are as follows:Ten samples were collected from Kaifeng in 2008 and all pure isolates of these samples were similar.According to its characteristics of morphology,pathogenicity test and sequence analysis of the internal transcribed spacer region of the ribosomal DNA(rDNA ITS ),the pathogen was identified as Colletotrichum gloeosporioides .The trial of the biological characteristics showed: the pathogen fungus could grow at 10-35℃,and the optimum temperature for mycelium growth was 28℃;and the range of pH was 3-10,the optimum were 6-7and the weakly acidic conditions were beneficial to sporification.The influence of different light envirments on the mycelium growth and sporification hadn't significant difference.Fructose and gulcose could promote the mycelium growth and starch could promote the sporification.Organic N source could stimulate C.gloeosporiodes to sporification ,when use (NH4)2SO4 as N source ,althought the mycelium could grow,the sporification is invariable.The lethal temperature for the spores was 50℃remaining for 10 minutes or 55℃remaining for 5minutes,while the lethal temperature for the mycelium was 60℃remaining 30 minutes or65℃remaining for 5 minutes.The trial of toxicity test of some common fungicides showed :Azoxystrobin had strong ?inhibition effect on the mycelium growth and spore germination.it provide a certain degree basis on the preventing and controlling of this disease.The pathogen fungus could produce toxin that arouse pathogenic symtoms in leaves were analogous with the pathogen infected the host plant when cultured in liquid medium.The trial showed that the basis constituent of the toxin was polysaccharide substance.And it's heat-stabilized.The effects of C.gloeosporioides phytotoxin on the tissue permeability,MDA content,POD,APX,and CAT activities of Osmantus fragrans leaves were studied by the analytical techniques in resistance.The results showed that C.gloeosporioides toxins increased the tissue permeability and the MDA content and membrane lipid overoxidation but lowered the POD,APX,and CAT activities in O.fragrans leaves.