Adjustment of medium composition and iso-osmotic potential in direct-shoot organogenesis produces true-to-type oil palm (Elaeis guineensis Jacq.) plantlets

Abstract

Clonally propagating elite lines of oil palm via multiple shoot organogenesis is promising due to genetic stability of regenerants. In this study, we tested the effects of medium composition using three basal media types (Murashige and Skoog (MS), woody plant medium (WPM), and Y3) with concentrations of sucrose and different ionic strengths derived from sucrose, sorbitol, or both sucrose and sorbitol on the growth and development of oil palm plantlets derived from direct-shoot organogenesis and zygotic embryo-derived seedlings (control). We used histological assays to better understand the medium formulation’s efficiency for shoot organogenesis. The shoot induction percentage was the highest when plantlets were cultured on ½ MS medium supplemented with 5% sucrose. A minimum osmotic potential of -2.0 MPa is essential to efficiently drive shoot maturation of oil palm. Sorbitol appeared to be less effective than sucrose for shoot formation of oil palms. To determine the rate of somoclonal changes between these two micropropagation methods, we investigated the rate of DNA methylation in oil palm plantlets using the methylation-sensitive amplification polymorphism (MSAP) technique. Our MSAP results showed that polymorphisms between in vitro seedling-derived plantlets and direct-shoot organogenesis-derived plantlets were considerably low. We conclude that regenerated plantlets derived from this established protocol are reliable for trueto- type propagation of elite oil palm clones.