Reproductive Biology, Pollination Optimization, and Hybrid Verification of Acacia mangium × A. auriculiformis

Acacia mangium × A. auriculiformis (hybrid acacia) combines high productivity with strong ecological adaptability and is therefore an important species for plantation establishment and germplasm innovation in southern China. Yet large-scale seed production has been constrained in Fujian by asynchronous flowering of the two parents, interspecific reproductive barriers, and the low efficiency of artificial pollination. The results show obvious spatial and temporal differences in the selected A. mangium, providing a basis for identifying suitable pollination windows. Ultra-low-temperature storage effectively maintained the long-term viability of A. auriculiformis pollen, providing a practical approach to alleviate asynchronous flowering between the parental species. Optimization of the liquid-pollination nutrient solution, pollen suspension system, and mentor-pollen proportion resulted in relatively high pod-set rates under field conditions for selected treatments. SLAF-seq generated 230,580 SLAF tags and 221,240 population-level SNPs. Combined evidence from SNP genotype concordance, principal component analysis, population structure, and phylogenetic analysis indicates that ZD15 and ZD16 show the strongest genetic evidence consistent with hybrid origin and are therefore regarded as the putative hybrid progeny with the strongest current genetic support, while M2 × DY5 is the most strongly supported candidate parental combination. These findings provide theoretical and technical support for germplasm innovation in hybrid acacia and for the development of more efficient and precise hybrid breeding strategies in Acacia.