Analysis of trait differences and identification of superior early growth combinations in interspecific hybrid progenies of Gleditsia sinensis

Interspecific hybridization is a key strategy for germplasm innovation in Gleditsia, yet systematic evaluations of hybrid progeny at the seedling stage remain limited. Effective interspecific breeding relies not only on parental compatibility but also on the genetic plasticity and environmental adaptability of the resulting progeny. A systematic analysis of progeny trait variation is therefore essential for developing informed breeding strategies, enhancing selection efficiency, and accelerating the hybridization process. In the present study, interspecific hybrids of Gleditsia were used as the experimental material. Specifically, Gleditsia sinensis served as the female parent and was crossed with four male parents: Gleditsia japonica var. delavayi, Gleditsia japonica, G. sinensis (intraspecific control), and Gleditsia fera. A comprehensive evaluation of progeny seedlings was conducted by comparing growth traits, root system characteristics, photosynthetic capacity, and chlorophyll fluorescence kinetics, with the aim of identifying superior traits and genetic potential among different hybrid combinations. Significant trait variation was observed among the hybrid combinations. Specifically, G. sinensis × G. fera exhibited superior stomatal conductance, high-light adaptation, average root diameter, and ground diameter, indicating strong hybrid compatibility. G. sinensis × G. delavayi showed the highest photochemical efficiency and electron transport rate, reflecting efficient light utilization. In contrast, G. sinensis × G. japonica performed poorly across most measured traits. Additionally, thorn number exhibited high heritability (h²=79.6%), confirming its utility as a reliable early selection indicator. These findings provide a theoretical foundation for early selection and prediction of environmental adaptability in Gleditsia interspecific hybrid seedlings.