A coordinated regeneration-selection strategy enables genetic transformation and rapid flowering in apple x pear intergeneric hybrids

Wide hybridization between related species and genera provides valuable opportunities for broadening genetic diversity and introducing desirable traits. In the tribe Maleae (Rosaceae), Malus (apple) and Pyrus (pear) are phylogenetically closely related, and apple x pear hybrids represent promising materials such as for disease-resistance breeding. However, the effective utilization of such hybrids in breeding programs is constrained by long juvenile period. In this study, we established a tissue culture-based regeneration and genetic transformation platform for apple x pear hybrids. Key stages affecting adventitious shoot regeneration were optimized, and appropriate ranges of antibiotic selection pressure and bacterial elimination conditions were systematically evaluated. Regeneration capacity was predominantly genotype-dependent and became further restricted under Agrobacterium infection, necessitating precise balancing between regeneration competence and selection pressure. Using the highly competence line and the established transformation system, MdFT1 gene was successfully introduced and over-expressed in intergeneric hybrids, resulting in transgenic plants exhibiting floral bud initiation approximately six months after infection under in vitro conditions. This study provides a practical and efficient regeneration-transformation framework for apple x pear hybrids and demonstrates its applicability for FT-mediated early flowering. The established system offers technical support for accelerated breeding strategies and facilitates the utilization of novel resources in genetic improvement of pome fruit.