| Cotinus coggygria is a famous ornamental tree, which constitute the main scenery of Beijing red leaves during autumn. However, verticillium wilt has emerged in recent years, which seriously affected the forest landscape and health, threatened the ecological environment construction in regions of Cotinus production worldwide. It has now considered the most devasting disease in smoke-trees. Since the disease is difficult to control, based on the predecessors research, we systematically exploration about the quantitative detection of pathogen and the interaction between the pathogen and the host. The main results are as follows:(1) Inoculating methods and the disease severity are closely connected. Dipping the root in conidial suspension lead the hosts quickly showed symptoms and finally cause the highest mortality. Soil inoculation can also cause the wilt disease, though the incidence process somewhat slower than the root dipping inoculation. Inoculate on the leaves can not lead to wilt symptoms. The pathogen can be found in plant residues during winter.(2) Test with the spectrophotometers, use3,3-diaminobenzidine (DAB), nitro-blue tetrazolium (NBT) and optical microscope to study the effects of infection causing by Verticillium dahliae on the oxidative state in the smoke trees. For a period of one month after the inoculation, activities of SOD, POD in smoke tree leaves were changed, firstly increased and then decreased, the value reached maximum at15dpi, when the leaves began to show susceptible symptoms. At the same time, production rate of O2-and H2O2showed increasing trend tendency and obvious accumulation by the late stage of the disease. Observation of cellular localization revealed that accompanied with a huge amount of ROS production in infected Cotinus leaves by late stage of the infection, then the cell died. According to the active changes of SOD and POD, and the main component of ROS content accumulation, it suggested that during early stage of the disease, ROS may involve in pathogen defense process, whereas when late stage of the disease, ROS may be responsible for cell death.(3)Establish an effective and rapid quantitative system by the use of specific primer and the SYBR Green dye with real-time PCR technology. The primer targeting the ITS region which can generate an187bp amplicon, the melt curve show a single dissociation peak at the same temperature proved its specificity. The minimal amount of pathogen DNA quantified is2pg. It’s sensitive enough to detect the pathogen both in the plant issues and the soil, even in the infected tree with symptomless. The results demonstrated that this new quantification PCR assay is reliable, reproducible and sensitive, it’s able to accurate detect and quantify the pathogen, predict the risk of disease before a damage threshold and gives prospect to understanding the pathogen spatiotemporal distribution of in the host, facilitate of the manage strategies making.(4)Use the quantitative system to study the relationship between different symptoms and the pathogen amount. The results showed that there is no straightforward relationship between different disease symptoms and pathogen quantity. But the pathogen in the plant tissues which show symptom is obvious higher than those in the planta look healthy, that indicated the pathogen should reach a certain number before they causes symptom. |
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