Genetic Evaluation and Selection of Growth Traits of Pinus kesiya var. langbianensis Half-Sib Families

Pinus kesiya var. langbianensis is a major commercial conifer in subtropical Yunnan, China, yet systematic genetic evaluation of its breeding populations remains scarce. We estimated genetic parameters for growth and stem form (SF) traits to support advanced-generation selection. In a progeny trial of 113 open-pollinated half-sib families established in 2013 at Pu’er, 2201 surviving trees were assessed at age 11 for height, diameter at breast height (DBH), stem volume, height to crown base (HCB), crown width, and an ordinal SF score. Variance components and breeding values (BVs) were estimated using linear mixed models, with a Bayesian threshold model as a sensitivity analysis for ordinal data. Family-mean heritabilities showed a gradient across growth traits (height 0.14, DBH 0.29, and volume 0.24). Stem volume had the highest genetic coefficient of variation (18.85%), the optimal selection target, whereas HCB lacked detectable genetic variance and SF was weakly controlled (0.09). Phenotypic and BV rankings diverged: although Yunjing Seed Orchard showed the highest phenotypic means, best linear unbiased prediction identified Jinggu Seed Orchard as contributing nine of the top ten families and 26 of the 35 elite individuals. A combined backward–forward strategy, ranking materials by volume BVs under a phenotypic threshold (SF ≥ 7), yielded predicted volume gains of 14.35% (family) and 15.01% (individual), providing a basis for second-cycle breeding pending multi-environment validation.