Occurrence of triploids in oil palm and their origin.

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.

Recovery of Oil Palm (Elaeis guineensis Jacq.) Somatic Embryos Cryostored For 20 Years.

　　BACKGROUND: A cryopreservation protocol has been established for oil palm somatic embryos (SEs), the efficiency of which must be evaluated, both in terms of regeneration and of long-term storage capacity, before its large-scale routine use. OBJECTIVE: To test the survival and recovery of 29 clones of oil palm somatic embryos cryostored for 20 years. MATERIALS AND METHODS: Clumps of SEs were pregrown for 7 days on medium containing 0.75 M sucrose, dehydrated in air-tight containers containing silica gel to moisture contents between 19-35% fresh weight, and then immersed directly in liquid nitrogen and stored in cryotanks for 20 years. RESULTS: Survival of SEs cryopreserved and rewarmed immediately displayed an average value of 19.1% for the 29 clones tested while survival of SEs rewarmed after 20 years of cryostorage was significantly higher, with an average of 33.2% for the 28 surviving clones. Out of these 28 surviving clones, three were lost due to contamination or regrowth decline, six produced only shoots and the rest proliferated. CONCLUSION: It is possible to cryostore oil palm SEs for extended periods and to regenerate proliferating cultures and plantlets from the cryopreserved material. The cryopreservation protocol established can thus be efficiently used to store oil palm germplasm and to manage large-scale production in industrial laboratories.

Field development of oil palms (Elaeis guineensis jacq) originating from cryopreserved stabilized polyembryonic cultures.

In this paper, the long term observation of plants originating from control and cryopreserved stabilized polyembryonic cultures (SPCs) of six elite oil palm clones was carried out. Survival of plantlets in the nursery was monitored, then a series of vegetative and floral characteristics of over 440 palms were studied for up to 12 years after field transfer in Côte D'Ivoire. The six clones tested showed an average recovery of 34% after freezing in liquid nitrogen. The average survival in the nursery of plantlets originating from pretreated and dehydrated and from cryopreserved SPCs was higher than that of control SPCs. Palm trees originating from control SPCs were found to flower earlier than those originating from pretreated and dehydrated and from cryopreserved SPCs. This delay in flowering disappeared progressively and all palms had flowered 3 years after planting regardless of the SPC treatment. Abnormal palms were observed in one clone only. With this clone, the percentage of abnormal palms originating from cryopreserved SPCs was significantly lower (5%) than that measured on palms originating from control SPCs (29%).

Possible sources of genetic resistance in oil palm (Elaeis guineensis Jacq.) to basal stem rot caused by Ganoderma boninense--prospects for future breeding.

Oil palm estates in southeast Asia suffer from substantial losses due to basal stem rot caused by Ganoderma boninense. Field observations have been carried out in North Sumatra, Indonesia, on a series of planting materials of known origin. Differences in susceptibility to the disease have been detected within the two Elaeis species, guineensis and oleifera. Within Elaeis guineensis, material of Deli origin is highly susceptible compared to material of African origin. It is also possible to detect differences in reaction between parents and between crosses within a given origin. The variability of resistance to basal stem rot within the same cross is also illustrated by the diverse responses of clones derived from palms of the same origin. The prospects opened up by these results are discussed, and the importance of performing an early selection test is highlighted.

Microsatellite-based high density linkage map in oil palm (Elaeis guineensis Jacq.).

A microsatellite-based high-density linkage map for oil palm (Elaeis guinensis Jacq.) was constructed from a cross between two heterozygous parents, a tenera palm from the La Me population (LM2T) and a dura palm from the Deli population (DA10D). A set of 390 simple sequence repeat (SSR) markers was developed in oil palm from microsatellite-enriched libraries and evaluated for polymorphism along with 21 coconut SSRs. A dense and genome-wide microsatellite framework as well as saturating amplified fragments length polymorphisms (AFLPs) allowed the construction of a linkage map consisting of 255 microsatellites, 688 AFLPs and the locus of the Sh gene, which controls the presence or absence of a shell in the oil palm fruit. An AFLP marker E-Agg/M-CAA132 was mapped at 4.7 cM from the Sh locus. The 944 genetic markers were distributed on 16 linkage groups (LGs) and covered 1,743 cM. Our linkage map is the first in oil palm to have 16 independent linkage groups corresponding to the plant's 16 homologous chromosome pairs. It is also the only high-density linkage map with as many microsatellite markers in an Arecaceae species and represents an important step towards quantitative trait loci analysis and physical mapping in the E. guineensis species.