Identification and Transcriptome Analysis of Bursaphelenchus xylophilus with Excellent Low Temperature Resistance

<i>Bursaphelenchus xylophilus</i> is one of the most destructive quarantine pests, causing irreversible damage to pine trees. However, the unexpected identification of pine wilt disease in Northern China indicates that <i>Bursaphelenchus xylophilus</i> can survive under low temperatures. In this study, we analyzed the reproductivity variations among 18 different isolates, and SC13 was identified to have excellent low temperature resistance. Subsequent molecular analysis of SC13 indicated its distinct gene expression under low temperatures. The epidermal growth factor, nematode cuticle collagen and G-protein-coupled receptor genes with environmental adaptation functions were demonstrated to be differentially expressed under low temperatures. Meanwhile, morphological observations also indicated that SC13 contained significantly more lipid drops in low-temperature treatments. Generally, the identification of representative <i>Bursaphelenchus xylophilus</i> isolates will facilitate relevant studies in the future, and the discovery of the gene expression and morphological changes of <i>Bursaphelenchus xylophilus</i> under low temperatures could expand the current understanding of the environmental adaption abilities of such invasive nematodes.