Comprehensive Evaluation of Hybrid Progeny of Catalpa Tree Species and Selection of Superior Hybrid Combinations

Hybrid breeding enhances forest genetic improvement by conferring offspring stronger vitality through gene recombination. This study used Catalpa bungei (Q), Catalpa fargesii f. duclouxi (D), and Catalpa fargesii (H) for artificial hybridization, with a natural C. fargesii f. duclouxi hybrid population as control. Mating types were DZ (D×D), HD (H×D), HQ (H×Q), QD (Q×D), and QQ (Q×Q). Annual growth and wood properties were analyzed to evaluate suitability for central China's low mountain hills and elucidate growth advantages. Results indicate: 1) Survival rates ranked QQ > QD > HQ > DZ > HD. Except 2012 height, mating types showed highly significant ( p  < 0.01) differences in H and DBH across years, and significant differences ( p  < 0.05) in Pilodyn and modulus of elasticity (MOE). Mating type × block interaction was significant only for 2020 MOE. 2) H and DBH growth trends were similar; QQ and DZ had significantly larger increments. QQ showed the smallest Pilodyn (24.5 mm, highest density) and largest MOE (6.5 GPa). 3) Height and DBH (2012, 2016, 2020) showed significant ( p  < 0.05) or highly significant ( p  < 0.01) correlations, strongest between 2016–2020. DBH correlated negatively with Pilodyn and positively with MOE. 4) Comprehensive Qi values ranked QQ (1.97) > QD (1.95) > DZ (1.85) > HD (1.80) > HQ (1.64), with QQ highest. Findings confirm QQ ( C. bungei × C. bungei ) is optimally suited for central China low mountain hills, providing support for Catalpa genetic improvement and economic utilization.