Somatic embryogenesis and genetic transformation in peony: challenges and applications

Paeonia, a traditional ornamental flower and economically important crop, requires efficient propagation and targeted breeding for sustainable industrial application. Somatic embryogenesis provides a potentially transformative method for regenerating and genetically transforming Paeonia, offering an alternative route for rapid propagation and precision breeding. However, SE application in Paeonia remains challenging due to strong genotype dependence and tissue culture recalcitrance. This review summarizes recent progress in understanding the key factors affecting SE efficiency, including the decisive role of genotype, explant selection, plant growth regulator combinations, and culture conditions. Critical bottlenecks limiting large-scale application are discussed, particularly browning and hyperhydricity. Additionally, this review covers advances in genetic transformation technologies for Paeonia, including both stable transformation via Agrobacterium-mediated systems and transient transformation approaches such as Agrobacterium infiltration and virus-induced gene silencing (VIGS) for functional genomics studies. Although significant progress has been achieved, key challenges remain including low regeneration efficiency, incomplete transformation systems, and genotype-dependent recalcitrance across most commercial cultivars. We identify critical bottlenecks and propose that future research should integrate optimized culture systems with emerging gene editing technologies to facilitate the development of new Paeonia cultivars, thereby enhancing industrial scalability and market competitiveness.