Pathogenicity of Three Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle. Isolates in Pinus koraiensis (Siebold & Zucc.) Seedlings

The pine wood nematode (PWN), Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle., is one of the most dangerous invasive species in the world, causing devastating pine wilt disease (PWD) in pine trees from many countries. The PWN is now established in 18 provinces in China from the south to north, and it has expanded to some areas of Liaoning Province with temperatures that are beyond the ideal range. It has been reported that Pinus koraiensis Siebold & Zucc., one of the representative pine trees of Liaoning Province, has been infected by PWNs. To investigate the pathogenicity of the PWN in P. koraiensis, the reproductive ability of PWNs on fungal culture was compared among three isolates: QH-1, NM-1, and CM-1 (QH-1 from Liaoning Province, NM-1 from Nanjing Province, and CM-1 from Chongqing Municipality). Four-year-old P. koraiensis seedlings were inoculated with QH-1, NM-1, and CM-1 at a rate of 2000 per seedling. Pathogenicity, external symptoms, and nematode migration were all monitored on a daily basis over the next few days. The results from the experiment showed that all three PWN isolates caused wilt in P. koraiensis seedlings, with QH-1 being more virulent than NM-1 and CM-1. In addition, QH-1 exhibited greater reproductive and migration abilities in the seedlings than NM-1 and CM-1. These results indicate that the virulence of the B. xylophilus isolates QH-1, NM-1, and CM-1 can differ in terms of seedling mortality, migration ability, and reproductive ability (in trees).