Abstract
ABSTRACTThe pine wood nematode (PWN; Bursaphelenchus xylophilus) is the causal agent of pine wilt disease, which results in severe ecological and economic losses in coniferous forests. During overwintering, PWNs undergo morphological and physiological changes to adapt to low temperature environments. Here, the physiological changes of the PWN populations sampled in the summer and winter were compared to analyze the role of low temperatures in their response. The PWN overwinters as third-stage dispersal juveniles, which showed significantly greater survival rates than summer populations (propagative forms) at sub-zero temperatures. The major biochemical compounds in the populations were analyzed by gas chromatography. Eight dominant fatty acids, with stearic acid being the most important, were identified from PWN propagative stage and third-stage dispersal stage. Compared with the propagative stage, the dispersal stage showed significant increases in the fatty acid content and the proportion of unsaturated fatty acids. Three carbohydrates, trehalose, glycerol and glucose, were detected in the PWN. Compared with the summer population, the levels of trehalose and glycerol increased significantly, while glucose decreased, in the winter population. The modifications in fatty acid composition and cryoprotectant levels, as elements of its changing physiology, play important roles in the overwintering success of the PWN.
Highlights
The pine wood nematode (PWN), Bursaphelenchus xylophilus (Nematode: Aphelenchoididae), is the causal agent of pine wilt disease (PWD), which causes severe ecological and economic losses in coniferous forests (Mota and Vieira, 2008)
To overcome low temperature-associated stresses in winter, the PWN molt to a particular developmental stage (JIII), which corresponds to the pre-dauer (J2) stages of C. elegans, but they can sustain the diapause stage for a long time (Zhao et al, 2007)
The low temperature survival rate was used to measure the cold tolerance of nematode
Summary
The pine wood nematode (PWN), Bursaphelenchus xylophilus (Nematode: Aphelenchoididae), is the causal agent of pine wilt disease (PWD), which causes severe ecological and economic losses in coniferous forests (Mota and Vieira, 2008). By 2007, PWN infections had been found in 113 Chinese counties of 12 provinces, with the coastal regions in the subtropical and warm-temperate zones of China (N 29°–34°), including Zhejiang. By 2018, PWN infections had been found in 315 Chinese counties of 16 provinces, with the northeast regions in the midtemperate zone of China (N 41°, E 124°), including Liaoning Provinces, being seriously affected (Provinces of Liaoning) (State Forestry Administration of the People’s Republic of China, 2018). The PWN may infest more areas in Northeastern China and expand further into high-latitude cold regions
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