The Study On Toona Sinensis Bacterial Leaf Spot Disease In Shandong Province

Bacterial leaf spot of Toona sinensis is a new discovered disease in Shandong Province,This disease brought harm to the leaves of Toona sinensis. At the early stage,light brown water logging polygonal or irregular spots appeared on the leaves,then the spots became brown gradually,the leaves would be died withered and exfoliated ultimately.In this thesis,the pathogen of bacterial leaf spot of Toona sinensis,was isolated,purified and identified as Xanthomonas campestris pv.campestris. The host range of the pathogen and the occurrence of this disease were studied. Some chemical and beneficial microorganisms to control the pathogen were selected.The changes of enzymes activity such as PAL,POD,PPO,SOD, CAT in Toona sinensis after infection of the pathogen were also tested.The main conclusions are as follows:1,From 2004 to 2008,more than 20 samples of bacterial leaf spot of Toona sinensis were collected from Jinan,Tai'an,Xintai,Ningyang,Binzhou, Linyi etc in Shandong province.39 bacterial strains(X-1～X-39) were isolated and purified.This is the first report that the pathogen of Bacterial leaf spot of Toona sinensis was identified as Xanthomonas campestris pv. campestris through identification of phenotypic characteristics,culture traits, morphology observation,determination of physiological and biochemical character,serology response and 16SrDNA sequence analysis.The 16SrDNA sequence of the pathogen has been registered in Genbank with accession number EU814440.2,This disease occurred from May to July each year and broke out in July, which was determined by field investigation and indoor experiment for 4 years. Humidity was the major factor to affect the happening of this disease.The pathogen in the residues could live on the natural surface soil or in the soil through the winter and could infect the host through stomas or wounds.The pathogen could be transmitted mainly by rain or by human activity etc. Secondary infection could be caused by diffused bacterium on the diseased leaves through splashing rain or friction in a growing season.3,The inhibition effect of 12 fungicides against bacterial leaf spot of Toona sinensis were measured by the method of suppressive zone.The results showed that 12.5%Carbendazim was effective to the disease,EC50 was 368.0665 mg·L^-1.4,Five enzyme activity in the host leaves were measured after the pathogen infected the local Toona sinensis.The result showed that the enzyme activity of PAL got maximum 5.67 U/g·min on the sixth day,which was 326 percentage higher than the contrast.There were two peaks in POD activity which on the fourth and eighth day with the activity 38.33 U/g·min,34.33 U/g·min respectively.SOD got its maximum value on the eighth day with the activity 309.85 U/g·min.CAT showed two activity peaks,which were on the fourth day and the eighth day,with the activity 3.00 U/g·min and 2.33 U/g·min respectively.