Genetic variation and early selection potential of Eucalyptus maideni F. v. Muell. half-sib families from seedling to early forest stages

To elucidate growth variation and adaptive differentiation of Eucalyptus maideni F. v. Muell. half-sib families from the nursery stage through early field establishment, we evaluated 15 half-sib families and one commercial control (CK). A multi-trait integrated assessment was first conducted at the nursery stage using the Smith–Hazel selection index (ISH). Progeny trials were subsequently established at three contrasting sites in Yunnan Province, China (Jinghong, Yiliang, and Shuangjiang), where growth and stem-form traits were monitored at 6, 12, and 18 months after planting. Genetic parameters and family breeding values (BVs) were estimated using linear mixed models (LMMs), with BVs predicted by best linear unbiased prediction (BLUP). Genotype × environment (G × E) interactions were further examined via genotype main effect plus G × E interaction (GGE) biplot analysis to jointly assess family adaptability, growth potential, and stability across environments. Results showed that major seedling traits exhibited highly significant among-family variation (P < 0.001), indicating strong genetic control; Families 14, 2, 5, 12, and 9 were identified as superior. After field establishment, family main effects remained highly significant for all traits across sites (P < 0.01), with most traits exhibiting moderate-to-high family heritability. Integrating survival rate, BLUP-derived BVs, and GGE-based stability metrics, Families 1, 5, 11, 8, and 12 were identified as core superior families. Moreover, Families 1, 11, 13, 14, and 15 consistently ranked among the best performers at two of the three sites, supporting site-specific deployment strategies tailored to target environmental zones.