- RB Cronje, E Hajari, IM Ratlapane, and A Jonker
- 2021
- Volume: 24
- Pg 33-39
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Our previous study has shown that ethephon application to litchi trees with hardened shoots in autumn successfully inhibited new flush growth prior to flowering, promoted carbohydrate accumulation and thus improved flowering. However, little is known about the mode of action of ethylene, the breakdown product of ethephon, in leaves and buds of litchi and whether ethylene has a direct effect on flowering-related genes. Therefore, an in-depth study was initiated to investigate the effect of ethephon applications on ethylene evolution, carbohydrate content and ethylene- and flowering-related gene expression levels in leaves and terminal buds. Ethephon was applied as a single full canopy spray at a concentration of 1000 ppm to trees with fully hardened flush during April 2018. Untreated trees served as a control. Ethylene release peaked two hours after application with a rapid and slow decrease thereafter in leaves and buds, respectively. The presence of ethylene in bud tissue delayed bud break in sprayed trees by approximately 21 days compared with unsprayed trees. The ethylene-related gene LcEIN3 and flower suppressor LcFLC were significantly expressed one day after ethephon application. Chlorophyll, sucrose and expression of the flowering gene LcFT2 were significantly increased at bud break in leaves of treated trees. A link between ethephon treatment, shoot maturity (measured as leaf chlorophyll content), leaf sucrose and gene expression of flowering genes at specific stages was established and showed that ethephon application has a direct effect on dormancy-related processes and subsequently an indirect effect on flowering.
Summary:
Study Focus: Examined how ethephon application influences ethylene evolution and expression of genes related to dormancy and flowering in ‘Mauritius’ litchi, helping understand its role in shoot growth control and flowering induction.
Effect on Ethylene: Ethephon stimulates ethylene production, a plant hormone that regulates bud dormancy by inhibiting new shoot flush and promoting readiness for flowering.
Gene Expression Changes: Application altered expression of dormancy-related and flowering genes, including those controlling bud break, floral initiation, and development, supporting efficient flowering in otherwise erratic conditions.
Physiological Result: The treatment induces bud dormancy during autumn, delaying flush growth but enhancing the proportion of pure floral panicles, improving flowering uniformity and yield potential.
Implications: Understanding these molecular and hormonal pathways helps optimize ethephon use to manage shoot growth and flowering timing in commercial litchi production for better yield and crop management.