Analysis Of The Population Variation Of Bursaphelenchus Xylophilus In Northern And Southern China

Bursaphelenchus xylophilus is the pathogenic nematode of pine wood nematode disease.It is classified as a quarantine pest in many countries and can harm many pines and cause their death.With the global warming,the suitable area of ??pine wood nematode in our country continues to expand,and human activities have also accelerated the long-distance spread of pine wood nematode disease.At present,the disease has spread from southern China to many cities,counties and districts in Liaoning Province,causing huge economic losses.In recent years,in response to the outbreak of B.xylophilus in Liaoning Province,China,this article has carried out a study on the differences in populations of B.xylophilus in northern and southern.This is of great significance to the exploration of the phenomenon and law of pine wood nematode disease spreading from the south to the north in china,as well as the prediction and control of the epidemic trend of pine wood nematode disease.In this paper,16 strains of pine wood nematodes from the northern and southern populations of China and the pine wood nematodes in the diseased wood in the Yaolingkou work area of the Jurong Forest Farm in Zhenjiang City are the research objects.By comparing the differences in morphology,pathogenicity and low temperature adaptability of the northern and southern strains.Based on the statistics of the survival rate of dispersal juveniles under extreme low temperature stress,the suitable areas of pine wood nematodes in China under the current temperature conditions are predicted,and the purpose is to study whether there are differences between the pine wood nematode strains in northern and southern China,and whether pine wood nematode disease continues to spread northward.The main findings are as follows:1.The morphological characteristics of the 16 strains have abundant variation within the strains,and there are certain differences among the strains.In general,the coefficient of variation of the body length of the northern strains is greater than that of the southern strains.The difference in female body length is more significant than that of males,and the body length of northern females is generally larger than that of southern females,the body width of the northern strain is slightly larger than that of the southern strain.The cluster analysis results of male and female adults of different strains of pine wood nematode based on morphological indicators showed that excluding individual strains,B.xylophilus showed the population differentiation of north and south strains on the overall level.The clustering of male and female adults does not appear inevitable connection,and the strains where the female adults gather together may not necessarily also gather together.2.The same strain showed different pathogenicity on different host pine trees,indicating that the pathogenicity of the strains has a certain host differentiation,and the pathogenicity of the pests from different host sources also showed certain differences.Although the difference in pathogenicity among strains of different geographical origins does not have absolute regularity,the difference in pathogenicity among the eight strains in Liaoning Province is smaller than that in Fujian,Guangxi,Guangdong,Jiangsu and Anhui Provinces.The pathogenicity of each strain is different,so the geographical origin factor seems to be greater than the host origin factor.There is no inevitable relationship between the pathogenicity of pine wood nematode and its morphology.3.The reproductive ability of the northern and southern B.xylophilus is different under different temperatures.The low temperature survival rate of the northern strains is better than that of the southern strains as a whole.Pine wood nematode accumulates a certain amount of fat in the body when faced with low temperature stress,and it mainly contains 10 fatty acids such as myristic acid(C14:0),oleic acid(C18:1)and linoleic acid(C18:2).The process of propagative larvae transformed into the dispersal larvae is accompanied by the accumulation of fat and the change of fatty acid composition,as well as the decrease of glucose and the increase of trehalose.4.The isotherm is defined by the meteorological data collected in January of the past 10 years,and the lethal temperature of the pine wood nematode under 30 day long-term and 24-hour short-term low temperature stress measured in this paper is used as the dividing line of the suitable zone to predict and divide B.xylophilus potentially suitable areas in China.The results showed that most areas of China are suitable for pine wood nematode,and pine wood nematode disease has a tendency to spread to the north.