Philippe Amblard

Genetic diversity and relationship in American and African oil palm as revealed by RFLP and AFLP molecular markers

Abstract – The objective of this work was to evaluate the genetic diversity, its organization and thegenetic relationships within oil palm ( Elaeis oleifera (Kunth) Cortes, from America, and E. guineensis(Jacq.), from Africa) germplasm using Restriction Fragment Length Polymorphism (RFLP) and AmplifiedFragment Length Polymorphism (AFLP). In complement to a previous RFLP study on 241 E. oleiferaaccessions, 38 E. guineensis accessions were analyzed using the same 37 cDNA probes. These accessionscovered a large part of the geographical distribution areas of these species in America and Africa. Inaddition, AFLP analysis was performed on a sub-set of 40 accessions of E. oleifera and 22 of E. guineensisusing three pairs of enzyme/primer combinations. Data were subjected to Factorial Analysis ofCorrespondence (FAC) and cluster analysis, with parameters of genetic diversity being also studied.Results appeared congruent between RFLP and AFLP. In the E. oleifera, AFLP confirmed the strongstructure of genetic diversity revealed by RFLP, according to geographical origin of the studied material,with the identification of the same four distinct genetic groups: Brazil, French Guyana/Surinam, Peru,north of Colombia/Central America. Both markers revealed that genetic divergence between the twospecies is of the same magnitude as that among provenances of E. oleifera. This finding is in discrepancywith the supposed early tertiary separation of the two species.Index terms: Elaeis oleifera, Elaeis guineensis, population genetics, palm species, genetic resources,molecular chacterization.Diversidade e relacao genetica entre o dende americano e o africanorevelada por marcadores moleculares do tipo RFLP e AFLPResumo – O objetivo deste trabalho foi avaliar a diversidade genetica, sua organizacao e a relacaogenetica no germoplasma de dende ( Elaeis oleifera (Kunth) Cortes, de origem americana, e E. guineensis(Jacq.), africana), pelas tecnicas de Polimorfismo de Comprimento de Fragmentos de Restricao (RestrictionFragment Length Polymorphism – RFLP) e Polimorfismo de Comprimento de Fragmentos Amplificados(Amplified Fragment Length Polymorphism – AFLP). Em complemento a um estudo previo de RFLPem 241 acessos de E. oleifera, 38 acessos de E. guineensis foram analisados usando as mesmas 37sondas de cDNA. Os acessos estudados cobrem uma grande parte da area de distribuicao geograficadestas duas especies nos continentes Americano e Africano, respectivamente. Alem disso, analises commarcadores AFLP foram realizadas em uma subamostra com 40 acessos de E. oleifera e 22 de E. guineensis,empregando tres combinacoes de pares enzima/primer. Os dados foram submetidos a analise fatorial decorrespondencia (AFC) e analise de cluster, sendo tambem estimados parâmetros de diversidade genetica.Os resultados obtidos apresentaram grande coerencia entre as duas tecnicas utilizadas, RFLP e AFLP.Na especie E. oleifera, a tecnica AFLP confirmou a forte estruturacao da diversidade genetica reveladapela tecnica de RFLP, de acordo com a origem geografica do material estudado e com a identificacao dosmesmos quatro grupos geneticos distintos: Brasil, Guiana Francesa/Suriname, Peru e norte da Colombia/America Central. Entretanto, ambos os marcadores revelaram que a divergencia entre as duas especiese da mesma magnitude da divergencia dentro da especie americana. Este resultado esta em discrepânciacom uma suposta separacao das duas especies durante a era terciaria.Termos para indexacao: Elaeis oleifera , Elaeis guineensis , genetica de populacao, palmeiras, recursosgeneticos, caracterizacao molecular.

Temporal and spatial expression of polygalacturonase gene family members reveals divergent regulation during fleshy fruit ripening and abscission in the monocot species oil palm

BackgroundCell separation that occurs during fleshy fruit abscission and dry fruit dehiscence facilitates seed dispersal, the final stage of plant reproductive development. While our understanding of the evolutionary context of cell separation is limited mainly to the eudicot model systems tomato and Arabidopsis, less is known about the mechanisms underlying fruit abscission in crop species, monocots in particular. The polygalacturonase (PG) multigene family encodes enzymes involved in the depolymerisation of pectin homogalacturonan within the primary cell wall and middle lamella. PG activity is commonly found in the separation layers during organ abscission and dehiscence, however, little is known about how this gene family has diverged since the separation of monocot and eudicots and the consequence of this divergence on the abscission process.ResultsThe objective of the current study was to identify PGs responsible for the high activity previously observed in the abscission zone (AZ) during fruit shedding of the tropical monocot oil palm, and to analyze PG gene expression during oil palm fruit ripening and abscission. We identified 14 transcripts that encode PGs, all of which are expressed in the base of the oil palm fruit. The accumulation of five PG transcripts increase, four decrease and five do not change during ethylene treatments that induce cell separation. One PG transcript (EgPG4) is the most highly induced in the fruit base, with a 700–5000 fold increase during the ethylene treatment. In situ hybridization experiments indicate that the EgPG4 transcript increases preferentially in the AZ cell layers in the base of the fruit in response to ethylene prior to cell separation.ConclusionsThe expression pattern of EgPG4 is consistent with the temporal and spatial requirements for cell separation to occur during oil palm fruit shedding. The sequence diversity of PGs and the complexity of their expression in the oil palm fruit tissues contrast with data from tomato, suggesting functional divergence underlying the ripening and abscission processes has occurred between these two fruit species. Furthermore, phylogenetic analysis of EgPG4 with PGs from other species suggests some conservation, but also diversification has occurred between monocots and eudicots, in particular between dry and fleshy fruit species.

Diffusion variétale du palmier à huile (Elaeis guineensis Jacq.)

La productivite du palmier a huile au cours du siecle passe a connu une croissance importante ou l’amelioration genetique a pris une large part. Elle a connu un rythme de croissance assez comparable a celui obtenu pour des plantes annuelles de pays temperes (ble, mais, tournesol, etc.). Il est possible de degager les etapes importantes qui ont marque l’histoire de l’amelioration. Apres une assez longue periode de selection massale, l’exploitation du gene « shell », dont l’heredite a ete decouverte par Beirnaert en 1939, a apporte une amelioration de 30% [1]. Vers 1960, l’exploitation de l’heterosis des croisements inter-origines apporte une nouvelle amelioration de 10% environ [2]. Enfin, deux cycles de selection recurrente ont ete acheves par differentes equipes et chacun a apporte 12 a 18% d’amelioration de la productivite. En 1991, la valeur moyenne des semences commerciales, plantees dans de bonnes conditions, etait proche de 6,7 tonnes d’huile par hectare et par an [3]. Aujourd’hui, elle est de l’ordre de 7,2 t/ha/an [4]. Ces gains quantitatifs ont ete accompagnes de progres qualitatifs importants comme la diminution de la vitesse de croissance, l’augmentation du pourcentage d’huile dans les regimes ou l’acquisition d’une forte resistance a la fusariose en Afrique de l’Ouest [5]. La qualite du futur materiel vegetal devrait etre sensiblement amelioree par l’utilisation d’une base genetique elargie dans les programmes d’amelioration [6]. En effet, les stations de recherche disposent d’une bonne diversite genetique rassemblee lors de nombreuses prospections realisees en Afrique (pour E. guineensis) et sur une espece apparentee en Amerique latine (pour E. oleifera). Ces collections apportent de nouveaux caracteres de qualite de l’huile, de resistance a la fusariose, qui sevit en Afrique, ou a la pourriture du cœur en Amerique latine. Le progres genetique disponible en experimentation doit etre integre dans les semences vulgarisees au plus vite et en quantite suffisante. Cependant, pour la reproduction du meilleur materiel, il existe des contraintes liees a la biologie des semences qui compliquent et ralentissent cette vulgarisation. En raison d’une dormance difficile a lever, les semences de palmier a huile sont distribuees sous forme de graines germees et leur distribution demande une organisation particuliere.

Gene coexpression network analysis of oil biosynthesis in an interspecific backcross of oil palm.

Global demand for vegetable oils is increasing at a dramatic rate, while our understanding of the regulation of oil biosynthesis in plants remains limited. To gain insights into the mechanisms that govern oil synthesis and fatty acid (FA) composition in the oil palm fruit, we used a multilevel approach combining gene coexpression analysis, quantification of allele-specific expression and joint multivariate analysis of transcriptomic and lipid data, in an interspecific backcross population between the African oil palm, Elaeis guineensis, and the American oil palm, Elaeis oleifera, which display contrasting oil contents and FA compositions. The gene coexpression network produced revealed tight transcriptional coordination of fatty acid synthesis (FAS) in the plastid with sugar sensing, plastidial glycolysis, transient starch storage and carbon recapture pathways. It also revealed a concerted regulation, along with FAS, of both the transfer of nascent FA to the endoplasmic reticulum, where triacylglycerol assembly occurs, and of the production of glycerol-3-phosphate, which provides the backbone of triacylglycerols. Plastid biogenesis and auxin transport were the two other biological processes most tightly connected to FAS in the network. In addition to WRINKLED1, a transcription factor (TF) known to activate FAS genes, two novel TFs, termed NF-YB-1 and ZFP-1, were found at the core of the FAS module. The saturated FA content of palm oil appeared to vary above all in relation to the level of transcripts of the gene coding for β-ketoacyl-acyl carrier protein synthase II. Our findings should facilitate the development of breeding and engineering strategies in this and other oil crops.

Cellular and pectin dynamics during abscission zone development and ripe fruit abscission of the monocot oil palm

The oil palm (Elaeis guineensis Jacq.) fruit primary abscission zone (AZ) is a multi-cell layered boundary region between the pedicel (P) and mesocarp (M) tissues. To examine the cellular processes that occur during the development and function of the AZ cell layers, we employed multiple histological and immunohistochemical methods combined with confocal, electron and Fourier-transform infrared (FT-IR) microspectroscopy approaches. During early fruit development and differentiation of the AZ, the orientation of cell divisions in the AZ was periclinal compared with anticlinal divisions in the P and M. AZ cell wall width increased earlier during development suggesting cell wall assembly occurred more rapidly in the AZ than the adjacent P and M tissues. The developing fruit AZ contain numerous intra-AZ cell layer plasmodesmata (PD), but very few inter-AZ cell layer PD. In the AZ of ripening fruit, PD were less frequent, wider, and mainly intra-AZ cell layer localized. Furthermore, DAPI staining revealed nuclei are located adjacent to PD and are remarkably aligned within AZ layer cells, and remain aligned and intact after cell separation. The polarized accumulation of ribosomes, rough endoplasmic reticulum, mitochondria, and vesicles suggested active secretion at the tip of AZ cells occurred during development which may contribute to the striated cell wall patterns in the AZ cell layers. AZ cells accumulated intracellular pectin during development, which appear to be released and/or degraded during cell separation. The signal for the JIM5 epitope, that recognizes low methylesterified and un-methylesterified homogalacturonan (HG), increased in the AZ layer cell walls prior to separation and dramatically increased on the separated AZ cell surfaces. Finally, FT-IR microspectroscopy analysis indicated a decrease in methylesterified HG occurred in AZ cell walls during separation, which may partially explain an increase in the JIM5 epitope signal. The results obtained through a multi-imaging approach allow an integrated view of the dynamic developmental processes that occur in a multi-layered boundary AZ and provide evidence for distinct regulatory mechanisms that underlie oil palm fruit AZ development and function.

Assessment of yocoboue wild oil palm (Elaeis guineensis Jacq.) from Côte d'Ivoire

Following a survey involving wild oil palm groves in Côte d’Ivoire as a whole in 1968, 17 parents were chosen at Yocoboué (southernCôte d’Ivoire). Agronomic performance of the 17 parents was assessed through Deli × Yocoboué hybrids in 3 trials grown at La Mé (Côte d’Ivoire), Mondoni and La Dibamba (Cameroon).When compared to the Deli × La Mé progenies used as controls, the Deli × Yocoboué hybrids produced 91% for total bunch weight and86% for oil yields. However, the genetic variability within the Deli × Yocoboué progenies allows to select individual progenies as productive as the Deli × La Mé controls, for breeding purposes. A study of major agronomic traits led to the choice of parent YO 11 T , which combines the largest number of favourable traits. On average, Deli × Yocobouéprogenies have slower vertical growth and are susceptible to Fusarium wilt, except 2 parents (YO 3 T and YO 9 T), which seem to be resistant.