Microbiology and Biotechnology Research: An Overview Vol. 11

Woody fruit trees have prolonged juvenile phases that substantially slow conventional breeding and delay the development of improved cultivars. This review evaluates selected case studies in which MADS-box gene overexpression was used to induce early flowering and shorten breeding cycles in apple, European pear and citrus. Particular emphasis is placed on the APETALA1/FRUITFULL clade and the silver birch BpMADS4 gene. In apple, constitutive BpMADS4 overexpression reduced a juvenile period of 4–5 years to less than 6 months and supported rapid cycle breeding in which four backcross generations were completed within 7 years. In European pear, BpMADS4-induced flowering occurred within 6–18 months after grafting, while transformed lines retained a comparatively normal tree-like architecture. In citrus, overexpression of Arabidopsis APETALA1 enabled fertile flowering in the first year after transformation while retaining environmentally responsive seasonal flowering. Collectively, these cases show that MADS-box-mediated flowering acceleration can substantially reduce generation time, although phenotypic outcomes vary among species. Important constraints include species-specific growth responses, transformation efficiency, environmental and rootstock effects, containment requirements, regulatory considerations and public acceptance. Integration with marker-assisted and genomic selection, together with gene-editing approaches, may further strengthen rapid-cycle breeding strategies. Overall, MADS-box-induced early flowering represents a promising approach for accelerating genetic improvement in perennial fruit crops while requiring careful species-specific evaluation.