Genetic variation and selection of Full sibling family of Fraxinus based on multi-point experiments

In this study, 22 intra- and interspecific full-sib Fraxinus families, generated from incomplete diallel crosses and grown for five years across three sites in Shandong Province, were used as experiment materials. Superior family selection was conducted through investigation of growth traits including tree height and diameter at breast height, analysis of variance, calculation of parental combining ability, as well as integrated analysis of genetic stability and adaptability. The results revealed substantial variation in growth traits among all tested families. The mean trait values of the optimal families were 21.36% to 73.32% higher than those of the poorest performing families, and 5.78% to 36.02% higher than those of the parental control. A significant interaction effect on family growth traits was detected across the three test sites. General combining ability analysis showed that parental clones ‘Lu La 6’, ‘Hong 2’, ‘Jinyebaila’, ‘Hong 4’ and ‘J30’ exhibited prominent superiority in tree height, while parental clones ‘Qingbi’, ‘Jinyebaila’, ‘Lu La 6’, ‘Hong 4’ and ‘J30’ delivered superior performance in diameter at breast height. Specific combining ability analysis identified two hybrid combinations with superior tree height performance and three combinations with superior diameter at breast height performance. Further analysis of these superior combinations, integrating phenotypic characteristics and fast-growing properties, revealed that four full-sib families, namely ‘Hybrid 42’, ‘Hybrid 46’, ‘Hybrid 69’ and ‘Hybrid 70’, had significantly or extremely significantly higher phenotypic values and heterosis in both diameter at breast height and tree height relative to all other hybrid combinations. Analysis of genotype by regional environment interaction effect, genetic stability and adaptability of the hybrid combinations demonstrated that ‘Hybrid 69’ and ‘Hybrid 70’ had low stability but strong adaptability to specific regions. ‘Hybrid 69’ exhibited distinct superior traits at different test sites, and also presented strong overall stress resistance.