Evaluation of stem diameter, Pilodyn penetration, and stress-wave velocity of stem in almost 320 clones of the first-generation plus trees of Chamaecyparis obtusa selected from the Kanto breeding region

Abstract Tree breeding programs in Japan have aimed to improve both growth and wood quality traits in Chamaecyparis obtusa . To enhance breeding for wood quality, it is essential to understand the genetic variability of traits related to growth, wood density, and stiffness. In the present study, we evaluated stem diameter (DBH), Pilodyn penetration (PP), and stress-wave velocity (SWV) in approximately 320 clones of first-generation plus trees of C. obtusa selected from the Kanto breeding region. All clones were planted in the breeding material stock garden in Ibaraki, Japan, and measurements were taken at age 28 years. Clonal repeatability for DBH, PP, and SWV was 0.474, 0.439, and 0.302, respectively, indicating that these traits can be improved by tree breeding. The genetic correlation between DBH and PP was positive ( r = 0.205), while that between DBH and SWV was low and negative ( r = − 0.150), suggesting the potential for simultaneous improvement of growth and stiffness. A total of 316 clones were grouped into four distinct groups, differing in clonal characteristics for growth and wood quality by cluster analysis, and several clones exhibited superior performance in both DBH and SWV. These findings provide valuable insights into the genetic variability of key traits in C. obtusa and contribute to the development of efficient selection strategies for wood quality improvement in future hinoki breeding programs.