The Study On Cold Tolerance Among Geographic Populations Of Pine Wood Nematode, Bursaphelenchus Xylophilus In China

Pine wood nematode(Bursaphelenchus xylophilus), is a important quarantine invasive species, which harm pine trees seriously. Since pine wilt disease was first discovered in China in 1982, it has caused huge economic losses. The growth and development of B.xylophilus was influenced by new environment, and the temperature is a vital factor to form new invasion for B.xylphilus. With the effect of the global climated warming and human activities on nature is getting much greater, the geographic distribution of pine wilt disease is getting larger in China in recent years, and it has threaten of continue to spread to the lower distribution of northern China. Therefor it’s important to study temperature extremes low temperature of B.xylophilus for early warning about potential distribution and its integrated control. The research study the cold tolerance ability, influencing factor and fecundity of different geographic group of B.xylophilus, which aimed to explore the difference of cold tolerance and physiological mechanism between geographic groups, then to assess the suitable geographic distribution and its potential temperature adaptive area in China. The main results are as follows:1. Propagative B.xylophilus has a strong ability to adapt above 0 ℃ temperature,but not survive well below 0 ℃ low temperature, so the cold tolerance mechanisms of propagative B.xylophilus may be chill tolerance. The cold acclimation enhanced the cold tolerance of B.xylophilus, and there was a positive correlation between the acclimation and cold tolerant, but there was no significant difference cold tolerant increase between 5℃and 0℃. The content of glycerol, glucose and trehalose was improved during acclimation period. Trehalose concentration show positive correlation with survival at-5℃.The nutritional status and culture temperature have influence on cold tolerance of B.xylophilus.2. The propagative and dispersal B.xylophilus from seven geographic groups was exposure at different low temperature.The result showed: Shanxi and Shandong groups showed stronger cold tolerance than other groups, while Guangdong and Guangxi groups are relatively weaker. The geographical differences may be caused by the difference of acclimation effect and physiological mechanism differences between groups. Fecundity determination showed that the population fecundity of Shanxi and Shandong groups is better than Guangdong and Guangxi Groups cultured at 25 ℃, but no at a high temperature (28℃ to 30 ℃).It indicated that there was correlation between the fecundity and optimum culture temperature B.xylophilus and geographical origin.3. Through the analysis of mean temperatures of in Jannuary and the lowest annual daily mean temperatures in five consecutive years from 62 meteorological stations among China, as the meteorological parameter, and combining with lethal temperature (LLT50 LLT75 LLT99) of B.xylophilus under the condition of low temperature for long-term (30 d) and short-term (1 d),we preliminary predicting potential distribution of B.xylophilus,and has defined highly, moderately, lowly adaptive and non- suitable distribution of B.xylophilus in China...