Transcriptomics of Three Larix Species in Response to Geographically Distinct Bursaphelenchus xylophilus Strains in China

Pine wood nematode (PWN, <i>Bursaphelenchus xylophilus</i>) is fatal to the pine trees around the world. Its northward and westward expansion in China endangers <i>Larix</i> spp., yet its molecular response remains understudied. We conducted transcriptomic analysis (RNA-seq) on three economically important larch species (<i>Larix principis-rupprechtii</i>, <i>L. olgensis</i>, and <i>L. kaempferi</i>) infected by geographically distinct PWN isolates (northern Fushun and southern Changde strains) at 1 and 3 days post-inoculation. Comparative RNA-seq analysis of 36 samples revealed that genes such as oxidative stress, and secondary metabolite production were differentially expressed in <i>Larix</i> spp. upon infection by the PWNs. Furthermore, compared to the Changde strain, infection with the Fushun PWN strain can elicit a consistently stronger and more distinct transcriptional defense response across all tested larch species. These results provide insights into the molecular mechanisms of plant defense against PWNs, offering genetic target for resistance breeding and informing the development of targeted control measures against this pathogen.