Influence Of Temperature On The Development Of Bursaphelenchus Xylophilus

Pine wood nematode disease is a devastating epidemic disease of pines, which is also called the pine wilt disease. Its pathogen Bursaphelenchus xylophilus is internationally recognized as important forestry biological quarantine object. Since found in Nanjing in 1982, the disease spread rapidly, caused serious economical and ecological disease in China.As invasive species B. xylophilus must be facing at the new ecological environment. It is worthy to discuss how it is suitable for the new environment and how to survive and breed. Since temperature is an important factor of ecological environment, in this study temperature as the breakthrough point, we discussed the nematode development process and duration under different temperature. We also studied the nematode sex ratio under different culture conditions, and preliminary study of sex determination genes. The major results studied in the experiment are abstracted as follows:We observed the ontogenesis of B. xylophilus at different temperature. There existed significant difference in embryonic development form, and in the development duration. With the temperature increasing the morphological index of B. xylophilus was increased, motility was also enhanced. The development period of B. xylophilus was affected by the temperature, with the increase of temperature the development period reduced. The post-embryonic development time of the different developmental stages account for different proportion of whole post-embryonic development time.We studied the significant difference of morphological in respond to the temperature. In optimum temperature 25? the embryo size and adult body length obtained the minimum value, with the increase or decrease of temperature the embryo size and adult body length were increased. The embryo size and adult body length obtained the max value at 15?. Though continuous domestication of 15?, we obtained the stable genetic line. After switched from 25? to 15?, the length of B. xylophilus increased. With the time increased the length minished and became stable at last.We studied the sex ratio of nematode under different culture environment. The nematode sex differentiation was affected by temperature, at different temperature the nematode sex radio showed regular changes. Between 20-25? the sex ratio obtained the maximum value. Different light conditions also affected the nematode sex ratio; the sex radio of B. xylophilus cultured in dark was bigger than it in light-dark. Artificial simulated the mating process at different sex radio, we found under different sex ratio the embryo size and morphology indexes existed significant difference, and 1:1 was largest since 3:1 was the smallest. Furthermore, we explored the sex determination critical period, and preliminary determined it was in embryo incubation stage.We cloned the sex determination gene mog-2. Analysis shows that the full length of the gene is 953bp, contains 110bp introne and a whole ORF of 843bp which encodes 280 amimo acids. The gene includes the intiation codon ATG and termination codon TGA. And the molecular weight of the predicted protein is 68.38kDa. Comparing the gene sequence with that on GeneDB, we find it has a 99.37% similarity. Comparing the amimo acids sequence with that on GeneDB, we find it has 98.58% similarity.