We induced male inflorescence on 162 oil palm trees of 14 years old by complete defoliation. Inflorescence emergence data was analysed within a five-year period. Total RNA was extracted from un-emerged inflorescence of both completely defoliated and non-defoliated trees for gene expression studies. The aim was to investigate the effects of voluntary time-specific inflorescence induction on the seasonal trend of inflorescence emergence; including the molecular mechanisms regulating inflorescence emergence in oil palm. Male inflorescence emergence increased by 104.2% after complete defoliation stress treatment. The time between induction and emergence of inflorescence was 17.83 months. There was an increase of 58.8% in male inflorescence emergence during the wet season as compared to the dry season although equal numbers of trees were treated for each season. Male inflorescence emergence was seasonal irrespective of the time or season of inflorescence induction, indicating that sex specific inflorescence emergence in oil palm is pre-programmed and synchronised, depending on seasonal cues. Response to carbohydrate status, light and temperature were among the highly enriched functional clusters obtained from 1,214 differentially expressed genes (DEG). Knowing the factors controlling inflorescence emergence, crop production estimation and breeding strategies can efficiently be designed by agronomists and breeders.
Key words: Defoliation, oil palm, voluntary inflorescence induction, seasonal cues, transcriptome analysis, RNA-Seq analysis
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