| The walnut with high nutritional value and economic value becomes more and more popular with people.And because of its lower cost of cultivation that was warmly welcomed by growers.Walnut planting areas expand unceasingly in recent years in Hechi,Guangxi Province.However,the large-scale planting of walnuts will face serious disease and pest problems,among them,walnut anthrax caused serious harm to the yield and quality of walnut fruits.In this paper,by using the method of indoor in vitro inoculation pathogens,studied the biological characteristics of walnut anthrax and its influence on physiological and biochemical of walnut leaves.Not only in theory will help to clarify relationship between walnut anthrax and walnuts and reveal the pathogenic mechanism of walnut anthrax and walnuts on resistance mechanism of anthrax,but also provide new ideas for prevention and control of walnut anthracnose.In this study,pathogen of walnut anthracnose in Hechi was identified by morphology and 16S rDNA sequence,and studied the biological characteristics of pathogenic bacteria and their effects on the physiological and biochemical of isolated walnut leaves,the results of the study are as following:1.Pathogen of walnut anthracnose in Hechi,Guangxi Province was identified as Collet.otrichum gloeosporioides based on its morphologic characters and 16S rDNA sequences analysis.The strain growed in the round in PDA medium with smooth edge,and the growth rate is 9.76 mm/d～12.5mm/d;hyphae developed,white fluffy,at start the colony was off white,then it became ash black and produced orange sor,conidium is single spore,long elliptical,length was 14μm～20μm,width was 4μm～7μm,both ends obtuse,colourless.2.Different cultivation had significant effects on the growth of strains.PDA medium was the most suitable for Colletotrichum gloeospo,rioides to grow,and SDA medium was the second one;the optimum growth temperature of Colletotrichum gloeosporioides was 28℃;the most suitable pH was 7.Different light processing had a big different influence on growth of pathogen of walnut anthracnose,the condition of total darkness was more advantageous for hypha to grow.Lethal temperature of Colletotrichum gloeosporioides as follow:57℃ for 15 min,58℃ for 12 min,59℃ for 9 min.The cellulase activity of the strain increased at first then decline,on the 7th day,cellulase activity was the largest,at 161.34 U/g.3.The infection of Colletotrichum gloeosporioides had a significant effect on the protective enzyme activity of walnut leaves.The activity of superoxide dismutase(SOD)and catalase(CAT)went up first and then down with the increase of the time of onset.The activity of superoxide dismutase in the third day was significantly higher than that of the control group,which was 1.79 times that of the control group;on the fifth day,the activity of superoxide dismutase decreased slightly,which was 1.76 times that of the control group;on the third and fifth day of onset,the catalase activity is significantly higher than the control group which was 1.25 times and 1.58 times that of control group.Instead,peroxidase(POD)activity increased at first,then descended with the time increasing,the peroxidase activity of the third day and the fifth day was significantly higher than that of the control group,which was 3.51 times and 3.61 times that of the control group.4.Changes of MDA,soluble protein and soluble sugar content in walnut leaves after inoculation with Colletotrichum gloeosporioides showed a rising trend with the extension of the time of onset,among them,the content of MDA was significantly higher than the control group in the third day and the fifth day,which was 1.15 times and 1.37 times that of the control group;but,there was no significant difference between soluble protein and soluble sugar content.5.The chlorophyll content of the leaves which inoculated with Colletotrichum gloeosporioides showed a decreasing trend with the extension of the time of onset.Among them,the chlorophyll content in the fifth day was significantly lower than the control,only 50.6%of the control group.6.Net photosynthetic rate of walnut leaves which infected with walnut anthracnose after seven days was significantly lower than healthy walnut leaves,which was 0.58 times of healthy walnut leaves;however,stomatal conductance,intercellular carbon dioxide concentration and transpiration rate of walnut leaves which infected with walnut anthracnose was higher than healthy walnut leaves that was 1.62 times,1.20 times,and 1.28 times as much as healthy walnut leaves,respectively,and these difference are not,significant. |
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