Overcoming Recalcitrance: A Review of Regeneration Methods and Challenges in Roses

Roses (Rosa spp.) are among the most economically and ornamentally important floricultural crops worldwide, yet their improvement is constrained by inefficient breeding methods. Tissue culture regeneration based plant transformation and genome editing technologies provide innovative and increasingly effective approaches to surmount these longstanding challenges; however, rose tissue culture regeneration remains notoriously recalcitrant. Successful plant regeneration in roses depends on multiple factors, including genotype, explant source, physiological status, and the precise combination of plant growth regulators and culture conditions. Over the past three decades, numerous efforts have focused on optimizing rose organogenesis and somatic embryogenesis systems. Despite progress, low regeneration frequencies, strong genotype dependency continue to limit molecular breeding and genome editing application in rose. This review synthesizes current advances in in vitro regeneration methods for roses, emphasizing key determinants of morphogenic response, including explant selection, hormonal balance, media composition, light and temperature regimes, and the organic and inorganic additives. The underlying causes of recalcitrance are discussed in relation to tissue physiology, biochemical and molecular regulation of morphogenesis. Finally, strategies for overcoming regeneration barriers-such as the use of morphogenic regulators and in planta transformation-are highlighted as emerging avenues toward cultivar independent transformation and genome editing for rose.