Geographical Distribution And Host Resisitance Of Poplar Canker In Shaanxi Province

Poplar canker is an important branch diseases of poplar, which has been reported more than 10 species of pathogenic bacteria in the world.? In China, poplar canker is caused frequently by Botryosphaeria ribis Grossenb. et Duggar and Valsa sordida Nit.. In order to better understand the geographical distribution of pathogenic and host resistance in Shaanxi province, the author investigated poplar canker in different regions of Shaanxi province, and did a preliminary study on different species of pathogen.The main conclusions are as following:(1) The study on the investigation and isolation of poplar canker'pathogen in different regions of Shaanxi Province showed that poplar canker had three main symptoms: blisters type, circinal spot type and bark rot type, including Dothiorella gregaria Sacc., Coniothyrium populinum Schulz. et Sacc., Cytospora chrysosperma Fr. and a few Fusarium sp.. Four kinds of poplar canker'pathogen were widely distributed in the middle of Shaanxi, and D. gregaria was the dominant species; poplar canker was mainly caused by Coniothyrium populinum Schulz. et Sacc. and Cytospora chrysosperma Fr. in northern Shaanxi; and few poplar canker was caused by D. gregaria Sacc. in southern Shaanxi.(2) Cultural characteristics showed that different kinds of poplar canker'pathogens or different strains of the same group of colony growth vary was different, of which the fastest was D. gregaria. Inoculating tests proved that D. gregaria showed more intense pathogenicity, C. populinum showed weaker pathogenicity, and both of them showed differentiation of culture character and pathogenic in Shaanxi province. Furthermore, D. gregaria, C. chrysosperma and Fusarium sp. showed significantly correlation between its growth rate and its pathogenic at the 0.05 level in the same strains, while C. populinum was not.(3) The survey data showed that the resistance varied significantly in different poplar species at the 0.05 level in the same area, the order of resistance in middle Shaanxi was: Populus deltoides×P. nigra > Populus alba×P. glandulosa > Populus×euramericana cv.'74/76'> Populus tomentosa, and the disease index of the same species varied significantly at the 0.05 level among different regions. The disease index of Populus tomentosa in middle Shaanxi was more serious than that in the north from Tongchuan. The disease index of Populus alba×Populus glandulosa was less serious in Mei County of Baoji than in Yaozhou of Tongchuan. There was not significant correlation between poplar canker disease index and poplar diameter (age of the trees) or the site conditions, however, there was significant correlation between poplar canker disease index and the poplar species or ecogeography at the 0.05 level.(4) The ITS-rDNA-PCR amplification of the 13 D. gregaria tested strains produced a single band spectrum, about 300bp, which was highly conservative, and thus proved the classification of species which based on colonial and anamorph morphological characters was almost correct.