Identifying a DELLA Gene as a Height Controlling Gene in Oil Palm

Abstract

The research in oil palm (Elaeis guineensis Jacq.) yield improvement is still being done to serve the consumption demand needed for cooking oil, cosmetics and biodiesel production. Moreover, a harvesting-facilitating trait such as stem height still needs more improvement to lower labor intensity and harvesting losses of oil palm bunches. This study aims to understand the genetic control for the stem height trait (HT) and its correlation with yield component traits such as bunch number (BN) and fresh fruit bunch yield (FFB). To identify height controlling genes, gene-based markers targeting three candidate genes including DELLA gene, gibberellin (GA) 2-oxidase and asparagine synthase were designed and identified the association of their potential polymorphic markers with HT in various oil palm populations. We identified the DELLA gene (renamed as EgDELLA1), a GA nuclear repressor, at chromosome 14, highly associated with height in the GT population at p value of 0.0261, and 0.0429 for the two of three times of height phenotype recorded. The strongest expressions of EgDELLA1 were found in apical meristem and, to a lesser extent in leaf and fruit development while no expression was detected in male inflorescence. This suggested that EgDELLA1 is a major component of stem elongation initiating at apical meristem. In addition, weak to moderate positive correlation was found between HT and BN (r = 0.215-0.395), and between HT and FFB (r = 0.254-0.499) from the KU and GT populations. Thus, improvement of semi-dwarf oil palm with higher yield is possible but still challenging. Our study provides some information that would be useful for oil palm variety improvement in the near future.