Nematocidal activity of the oomycete Lagenidium juracyae against pine wood nematode

Abstract BACKGROUND Pine wilt disease is a global quarantine disease caused by the pine wood nematode, Bursaphelenchus xylophilus . It has been the most serious forest disease in recent decades globally; however, no approved countermeasures have been developed. Existing nematocidal biocontrol agents are derived mainly from fungi and bacteria, and research on oomycete nematocidal agents is rare. A strain capable of killing B. xylophilus , the oomycete Lagenidium sp. NL03, was isolated from the corpses of Rhabditidae soil nematodes. RESULTS Based on its morphology and molecular biology, the strain was identified as Lagenidium juracyae . L. juracyae could produce kidney‐shaped biflagellate zoospores that could kill pine wood nematode, with a nematocidal efficiency of 60% at a zoospore concentration of >1.5 × 10 4 mL −1 . Among second‐stage juveniles, third‐stage juveniles (J3), fourth‐stage juveniles (J4), and adults, J3 and J4 were more susceptible to infestation. Meanwhile, the zoospore suspension and the cytoplasmic extract of L. juracyae inhibited egg hatching and nematode motility significantly. RNA‐seq data analysis indicated that the KEGG pathways of ‘Glycerolipid metabolism’, ‘ABC transporters’, ‘Ribosome’, ‘Tyrosine metabolism’, and the effectors of RxLR and CRN were involved in the infection processes of the oomycetes. CONCLUSION L. juracyae kills nematodes via zoospore adhesion. Its zoospores have recognition and infection ability, and the L. juracyae cytoplasmic extract and zoospore suspension can inhibit nematode hatching and motility significantly. Glycerolipid and Tyrosine metabolism‐related pathways may participate in the infection. The present study enhances our understanding of oomycete activity against nematodes, which could facilitate the control of the invasive nematode. © 2025 Society of Chemical Industry.