Cold adaptive potential of pine wood nematodes overwintering in plant hosts

Abstract

The 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.

Spatiotemporal Dynamics and Factors Driving the Distributions of Pine Wilt Disease-Damaged Forests in China

“…Short-term environmental factors also contributed significantly to the PWD outbreaks in 2008 and 2018. Temperature-related environmental factors are known to be important indicators of PWD outbreaks, with low temperatures inhibiting the transmission of PWD and delaying the PWN life cycle [16][17][18]. However, our results did not show a good relationship between temperature and PWD outbreaks.…”

“…Temperature and precipitation are the primary climatic factors associated with these outbreaks [2,14,15]. Warm winter temperatures enhance the survival of overwintering populations of PWN, whereas cold temperatures retard its spread and delay its life cycle [16][17][18]. Previous studies have demonstrated that PWD has never occurred when the mean air temperature is <20 • C in the warmest month or <−10 • C in the coldest month [15,19].…”

Genetic characteristics of Bursaphelenchus xylophilus third-stage dispersal juveniles

“…of DJ3 is slightly larger and accumulates many lipid droplets 13,16,26 . In previous studies, the percentage of DJ3 in standing trees in the field increased with time, reaching 60-100% by winter 15,29 , which might be related to their survival in a low-temperature environment, indicating a greater risk of its spread to low temperature areas. Therefore, additional studies are urgently needed to illustrate the mechanism of DJ3 formation and PWN survival under low temperatures.…”

Current Insights into Migratory Endoparasitism: Deciphering the Biology, Parasitism Mechanisms, and Management Strategies of Key Migratory Endoparasitic Phytonematodes

“…Another migratory PPN, B. xylophilus, has been shown to overwinter in both living and dead tissues of coniferous trees, allowing it to endure long, harsh winters [29]. However, the molecular mechanisms underpinning cold tolerance in PPNs are multipartite and poorly understood at present [30]. Homologs of dauer genes have also been found in the genomic and transcriptome analysis of the burrowing nematode R. similis; however, since R. similis has not been shown to form dauers, the roles of these genes remain unclear [14,19].…”