Annals of Botany: Occurrence of triploids in oil palm and their origin
Etude confirmant et détaillant le processus de polyploïdisation sexuelle chez le palmier à huile en identifiant également trois traits phénotypiques permettant d'évaluer le niveau de ploïdie des palmiers à huile géants au champ.
Pomiès V., Turnbull N., Le Squin S., Syahputra I., Suryana E., Durand-Gasselin T., Cochard B., Bakry F. Occurrence of triploids in oil palm and their origin. Annals of Botany, Oxford University Press (OUP), 2022
https://doi.org/10.1093/aob/mcac036
Abstract
Background and Aims
Oil palms showing exceptional vigour and dubbed as ‘giant palms’ were identified in some progeny during breeding. A panel of phenotypical traits were studied to characterize these trees. The hypothesis that gigantism and other anomalies might be linked to polyploidy was investigated.
Methods
Twenty sib pairs of palms from different crosses, each comprising a giant and a normal oil palm, were studied by flow cytometry with rice ‘Nipponbare’ as standard reference. In parallel, palms were assessed in the field using 11 phenotypic traits. A principal component analysis (PCA) was conducted to define relationships between these phenotypical traits, and a linear discriminant analysis (LDA) to predict ploidy level and giant classification. Finally, a co-dominant molecular marker study was implemented to highlight the sexual process leading to the formation of 2n gametes.
Key Results
The first group of oil palms presented an oil palm/rice peak ratio of around 4.8 corresponding to diploid oil palms, whereas the second group presented a ratio of around 7, classifying these plants as triploid. The PCA enabled the classification of the plants in three classes: 21 were normal diploid palms; ten were giant diploid palms; while 11 were giant triploid palms. The LDA revealed three predictors for ploidy classification: phyllotaxy, petiole size and circumference of the plant, but surprisingly not height. The molecular study revealed that triploid palms arose from 2n gametes resulting from the second division restitution of meiosis in parents.
Conclusions
This study confirms and details the process of sexual polyploidization in oil palm. It also identifies three phenotypical traits to assess the ploidy level of the giant oil palms in the field. In practical terms, our results provide a cheap scientific method to identify polyploid palms in the field.
Publiée : 02/11/2022