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Scientia Silvae Sinicae ›› 2025, Vol. 61 ›› Issue (1): 137-149.doi: 10.11707/j.1001-7488.LYKX20220760

• Research papers • Previous Articles     Next Articles

Phenotypic Variation of Bursaphelenchus xylophilus in Different Occurrence Areas of Zhejiang Province

Zhihong Li1,2(),Wei Zhang1,Xinkang Zhao3,Jinping Shu1,*(),Haojie Wang1   

  1. 1. Research Institute of Subtropical Forestry, Chinese Academy of Forestry Hangzhou 311400
    2. Nanjing Forestry University Nanjing 210037
    3. Zhejiang A & F University Hangzhou 311300
  • Received:2022-11-07 Online:2025-01-25 Published:2025-02-09
  • Contact: Jinping Shu E-mail:lizhihong927@126.com;jpshu@caf.ac.cn

Abstract:

Objective: This study aims to reveal the morphological adaptation mechanism and provide important information for phenotypic tracing of Bursaphelenchus xylophilus, by investigating the morphological characteristics and phenotypic variation of B. xylophilus under different terrain conditions in different infected areas. Method: Zhejiang Province, where the pine wood nematode invaded earlier, was selected as the sampling area. The pine wood nematode epidemic areas in Zhejiang Province were divided into 18 districts and 19 regions based on the invasion time and the topographic habitats of pine wood nematode, where the samples were collected and the nematode was isolated and purified. Seven morphological indices related to adult female and male nematodes, individual development, feeding, and reproduction were determined. These indices included body length, body width, median bulb width, stylet length, tail length, anus body width, and spicule length. The phenotypic variation of B. xylophilus was analyzed by hierarchical cluster analysis and variation analysis to identify distinct morphological indicators. Result: 1) There are abundant phenotypic variations in B. xylophilus adults in different regions of Zhejiang Province, and female nematodes were significantly larger than males in several morphological indices. The results of variation analysis showed that the morphological variation of B. xylophilus primarily occurred in feeding-related morphological indices. Among the morphological indicators of female and male nematodes, median bulb width and stylet length of male and female adults varied significantly, while the body length and tail length were relatively stable morphological indicators. The spicule length was a morphological feature with less variation in male pine wood nematodes. 2) Hierarchical clustering analysis with multiple indicators showed that the female and male adult pine wood nematodes from the 19 sampling regions were all divided into three different clusters, but the clustering results of female and male were inconsistent. The clustering results of male nematodes were related to individual reproductive indices, while those of female nematodes were related to individual growth and development indices. There was randomness in relation to the invasion time and colonization habitat of the pine wood nematodes. PLS-DA analysis indicates that body length, body width, and tail length were the main morphological indicators for clustering female nematodes, while body length, tail length, and spicule length were the main indicators for clustering male nematodes. 3) The morphology of B. xylophilus changed in environmental adaptation, with the nematode morphology of northern populations larger than that of southern populations, and the morphology of nematodes in colonized areas larger than that in invaded areas. Altitude had an impact on the morphology of female. 4) In environmental adaptation, the rate of morphological differentiation in females was greater than that in males. The morphological variation of females tended towards individual growth and development, while that of males tended towards reproductive development. Conclusion: Terrain and invasion time affect the morphology of pine wood nematode, and the significant phenotype variations of B. xylophilus mainly occur in the morphological characteristics related to feeding. Body length, tail length and spicule length may be key morphological features for phenotype tracing of B. xylophilus on a large scale. The degree and direction of variation in female and male adults are inconsistent.

Key words: Bursaphelenchus xylophilus, pine wood disease, morphological characteristics, phenotypic variation, morphological diversifications

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