Cytokinins influence bulblet formation by modulating sugar metabolism and endogenous hormones in Asiatic hybrid lily

Lilies are bulbous flowers cherished for their aesthetic and medicinal value. Within the realm of lily cultivation, scale-cutting serves as a prevailing method for vegetative propagation, yielding diminutive bulbs termed bulblets at the base of scales. However, the burgeoning demand for lilies necessitates the optimization of propagation strategies to satisfy the surging requisites. This study centers on two synthetic cytokinin analogs, N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU) and 2-isopentenyladenine (2-iP), identified for their capacity to amplify bulblet formation within the Asiatic hybrid lily cultivar 'Matrix'. This dynamic process encompasses two pivotal phases: initiation and development. During bulblet initiation, the basal region of the maternal scale, subject to CPPU and 2-iP treatment, exhibited an elevation in the expression of cytokinin receptor genes (LaAHK2/3/4) and an augmented GA3/ZT ratio in comparison to the control, concomitant with a decrease in the IAA/ZT ratio. Moreover, CPPU and 2-iP treatments caused a notable upregulation of sucrose metabolism genes. During bulblet development stage, CPPU and 2-iP treatments invoked an augmentation in both the diameter and mass of the bulblets. The CPPU treatment accentuated the accumulation of GA3, while the 2-iP treatment effectively fostered the accrual of IAA. Additionally, both CPPU and 2-iP treatments expedited the pace of sucrose utilization and the accumulation of starch during bulblet development. This enhanced metabolic activity was conjoined by a substantial upregulation of genes linked to sucrose metabolism. Here, we underscore the proficiency of CPPU and 2-iP in elevating the formation of lily bulblets through their orchestrated impact on hormone levels and sucrose metabolism.