Molecular mechanisms underlying floral trait formation in Phalaenopsis orchids

Phalaenopsis orchids are one of the most important ornamental crops, prized for their beautiful flowers and long flowering phase. Hundreds of commercially available cultivars display a remarkable range of variation in key horticultural traits, including inflorescence type, floral size, and color patterning. While most current cultivars have been developed through cross-breeding or mutation breeding, genetic homogenization has become a growing concern. This is largely due to extensive hybridization among existing cultivars, which are predominantly derived from a limited number of parental species. Additionally, trait linkage in Phal. can hinder the integration of desirable characteristics in progeny. Therefore, there is an urgent need to decipher the genetic programs governing key horticultural traits to facilitate both conventional and molecular breeding. Despite significant research efforts, progress has been hampered by several resource limitations. These include a scarcity of high-quality genome assemblies, the lack of stable genetic transformation systems, and insufficient materials for molecular biology studies-a challenge exacerbated by the plant's relatively long life cycle. Consequently, the molecular mechanisms underlying the formation and diversity of most important horticultural traits in Phal. orchids remain largely unexplored. This review summarizes recent research advances, with a primary focus on the key floral traits in Phal. orchids, including inflorescence type, flowering time, floral organ organization, color patterning, size, longevity, scent, organ shape, cuticle production, and wax biosynthesis. Furthermore, we offer perspectives on future research directions aimed at elucidating the genetic basis for the remarkable diversity of these traits and advancing molecular breeding in Phal. orchids.