Toward Tissue-Free Plant Engineering: Emerging Platforms for Sustainable Horticultural Transformation

Genetic transformation in horticultural crops is being reshaped by the emergence of nontissue culture technologies that bypass entrenched barriers of genotype dependence, regeneration inefficiency, and sterile culture requirements. This review surveys recent in planta methods, including regenerative activity-dependent in Planta injection delivery (RAPID), cut-dip-budding (CDB), virus-based delivery, nanoparticle-mediated transformation, and Agrobacterium rhizogenes-induced regeneration, and evaluates their operational versatility across species. We further examine their integration with developmental regulators (BABY BOOM [BBM], WUSCHEL [WUS]), visual markers (RUBY), and CRISPR/Cas systems to enhance transformation efficiency and precision. Case studies across fruit, vegetable, and ornamental crops illustrate broad applicability and growing technical maturity. Despite these advances, unresolved challenges in biosafety, reproducibility, and regulatory alignment remain. We advocate a new transformation paradigm that is rapid, genotype-independent, and environmentally compatible, enabling scalable and more accessible broadly applicable crop improvement in horticultural biotechnology.