The Infection Way Of Wetwood Disease Pathogens Of Poplar And Their Effects On The Growth Of Poplar

Poplar(Populus spp.) is a kind of deciduous tree which is the most significant tree species planted in short-cycle industrial raw material forest and applied for developing ecological protective forest in China. But high incidence and serious situation of wet-wood-disease of poplar limited the development of the poplar and its processing and manufacturing. Hence wet-wood-disease of poplar is a big problem to be solved on the current production of poplar. This essay focuses on studying the invasion pathways of pathogen of wet-wood-disease of poplar, which were renamed pb1 and pb2 belong to Pectobacterium spp., and the characteristic of pathological site of infected poplar, and some morphological and physiological indicators to analysis the influence of pb1 and pb2 on poplar growth, providing the reference for studying the pathogenic mechanism of wet-wood-disease and preventing and controlling of wet-wood-disease. The results are as follows:(1)Only the wounds on the stem caused by stem-injecting method and stem-cutting inoculation method can make the healthy poplar infected by exogenous pathogen strains pb1 and pb2, whereas root-irrigating method, leaf-cutting method and stem-daubing inoculation method cannot infect the poplar. Pathogen strains pb1 and pb2 infected the poplar through the wound of stem of poplar, in which pathogen strains pb1 has the stronger pathogenicity. In addition, the stem-injecting is the easiest way to make the poplar affected the disease.(2) Compared with control groups, the plant height, ground diameter, leaf area, total length of roots, total surface area of roots, total roots volume of 1 year and 2 year old poplar Nanlin895 and Zhongshi NO.8 were inhibited, where the pathogen strains pb1 had lager influence on the poplar than the pathogen strains pb2, besides those, the fresh and dry weight of roots, stems and leaves of one year and two year old poplar Nanlin895 and Zhongshi NO.8 were decreased. The pathogen strains affected the organ of poplar in the sequence of roots>stems>leaves, the pathogen strains pb1 has lager influence on them than the pathogen strains pb2, and 2 year old were affected more.(3) Compared with control groups, the content of the chlorophyll a, chlorophyll b, the total chlorophyll and carotenoid of leaves of the poplar were decreased, and the poplar inoculated pb1 were affected more. Daily variation of Pn、Tr、Ci、Gs of the poplar presented single apex trend, and their peak value were significantly declined, and the value of the poplar inoculated pb1 decreased more.(4) The total accumulations of element K, Ca, Mg, Mn, Zn and Cu in different organs of the poplar were ranked in the order of leaves>roots>stems, whereas the element Fe was roots > leaves > stems, after inoculated pb1 and pb2, the total accumulations of the element K、Ca、Mg in different organs were ranked in leaves>stems>roots; the element Fe was still leaves>roots>stems; the element Mn and Zn were leaves>stems, roots>stems, alomost same with that in roots and stems; the element Cu was sill leaves>roots>stems.Such allocation resulted in that the content of element K, Ca, Mg, Fe, Mn, Zn and Cu of the stems of the one year and two year old poplar Nanlin895 and Zhongshi NO.8 inoculated pb1 and pb2, were higher than control group, particularly K, Ca, Mg and Fe were increased more significantly.The content of element K, Ca, Mg, Fe, Zn and Cu of the leaves of the one year and two year old poplar Nanlin895 and Zhongshi NO.1 inoculated pb1 and pb2,were lower than control group, and the poplar inoculated pb1 were affected more.(5) Comparing the influence of pathogenic bacteria on the pathological feature of infection site of the poplar, the p H values of the infection site of the control group were neutral, however, the poplar inoculated pb1 and pb2 were alkaline, and the poplar inoculated pb1 were higher, and two year old poplars were also higher. As for the lengths of color changing of stems, two year old poplars were longer, and the poplar inoculated pb1 were longer. In the aspect of color changing ratios of stems, the value of the poplar Zhongshi NO.8 were larger than the poplar Nanlin895, and the poplar inoculated pb1 were larger. The moisture content stems of the poplar inoculated pb1 and pb2 were higher than the control groups. There were a large number of bacteria in the inner wall of xylem vessels of the poplar inoculated pb1 and pb2, and some intercellular layer between the tracheids were degraded.