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Phoeniciculture, or date palm cultivation plays a major socio-economic and ecological role. However, few studies have quantified the drivers of date palm cultivation and its socio-economic and environmental benefits in West African Sahel. Therefore, this study assessed the effect of anthropic and environmental factors on quantitative and qualitative production of dates palm in Niger. We conducted an ethnobotanical survey to collect data in the Sahelian and Saharian zones of Niger. We used permutation regression test to assess the influence of climatic conditions, fidelity of cultural practices implementation and the socio-economic level of producers on the date palm profitability. The Spearman rank correlation coefficients between the economic parameters and the geographical position of palm groves were also estimated based on the Spearman rank permutation test. A total of 60 producers were surveyed in ten villages of Sahelian and Saharian zones known as two main phoenicicultural areas in Niger. This analysis showed that date palm production varies quantitatively and qualitatively across agro-ecological zones. The study revealed also that ethnic groups influence the quantitative aspect of date palm production (P = 0.023), by socioeconomic parameters (P = 0.005) and by the index of fidelity to the cultural practice implementation (P = 0.035). The date palm production varies quantitatively (P = 0.001) and qualitatively (P = 0.033) according to the agro-climatic zones. The Spearman rank test shows a significant correlation between the quantitative and qualitative production, the geographical position of the palm groves and the depth of the water table. The profitability of the date palm seems not to be up to the phoenicicultural potential that can be the consequence of the poor implementation of the cultural practices, the socio-economic level of the producers and the environmental conditions.

Genetic and morphometric analysis of germinated ancient date seeds provide initial insights into origins of the Judean date palm., Germination of 2000-year-old seeds of Phoenix dactylifera from Judean desert archaeological sites provides a unique opportunity to study the Judean date palm, described in antiquity for the quality, size, and medicinal properties of its fruit, but lost for centuries. Microsatellite genotyping of germinated seeds indicates that exchanges of genetic material occurred between the Middle East (eastern) and North Africa (western) date palm gene pools, with older seeds exhibiting a more eastern nuclear genome on a gradient from east to west of genetic contributions. Ancient seeds were significantly longer and wider than modern varieties, supporting historical records of the large size of the Judean date. These findings, in accord with the region’s location between east and west date palm gene pools, suggest that sophisticated agricultural practices may have contributed to the Judean date’s historical reputation. Given its exceptional storage potentialities, the date palm is a remarkable model for seed longevity research.

The cultivation of date palm, a pillar of oasis agrosystem constitutes a real source of development in arid and semi-arid zones because of its fruit’s rich in sugars and various products, essential to daily life of the populations. In Chad, date production has experienced a decline since the sixties, in relation to diseases, pests and poorly performing cultivation techniques, environmental factors are major causes of the degradation of phoeniculture as well as insecurity and the phenomenon of rural exodus. In order to assess the potential of oasis agroecosystems based on the date palm in Chad, an ethnobotanical survey was carried out among date farmers of Sahara and Sahel. The cultivars of date palm is mainly cultivated in Sahara in the North of the country where it allows a rich and diversified subsistence agriculture (market gardening, fruit trees, cereals and fodder), which excludes the use of chemical inputs in production. Our study made it possible to highlight an important genetic diversity with more than 200 cultivars, resulting from empirical selection and multiplied by offshoot. In Sahara, date palms cultivars have only one fruit production season per year with satisfactory productivity, an acceptable price and farmers have a good knowledge of cultivation practises. In central part of the country corresponding to the Sahelian zone, oasis agrosystems are also found in basins. The climatic conditions favour two production seasons and the income from the sale of dates from the first fruit production season (April and May) is greater than those from the second production season (June to September). The strengthening of the local knowledge and the extension of palm groves made it possible to increase production and income and would contribute to food security and the maintenance of populations in Chad and more generally in Sahel’s countries.

International audience; Date palm (Phoenix dactylifera L.) is mainly cultivated for its edible fruit and is of great socio-economic importance for the populations of arid zones. Analysis of the date palm genetic diversity in the Old World had revealed a strong genetic structure with the existence of two gene pools, one Eastern comprising Asia and Djibouti, and one Western, consisting of North African accessions. So far, mainly date palm populations from countries within the Maghreb and the Middle East were characterized, but no information from the Sahel was included. Here, we present the genetic diversity of date palms from Southeastern Niger. The DNA of 113 date palm accessions were analyzed and compared with a database containing the genetic information of 248 accessions from the Old World. The diversity generated from microsatellite markers was compared to that of the same loci of both the Eastern and Western genetic pools. Our results show that date palms from Southeastern Niger constitute a unique group with a high level of genetic diversity. Moreover, even though this group is included in the Western genetic pool, it shows a specific originality which differentiates it from other Western populations. It also shows one of the lowest admixture levels of the Western pool. Global analysis showed a secondary genetic structure within the Western pool highlighting a new genetic group located in Southeastern Niger that distinguishes itself from the North African group.

International audience; Understanding the driving forces and molecular processes underlying dioecy and sex chromosome evolution, leading from hermaphroditism to the occurrence of male and female individuals, is of considerable interest in fundamental and applied research. The genus Phoenix, belonging to the Arecaceae family, consists uniquely of dioecious species. Phylogenetic data suggest that the genus Phoenix has diverged from a hermaphroditic ancestor which is also shared with its closest relatives. We have investigated the cessation of recombination in the sex-determination region within the genus Phoenix as a whole by extending the analysis of P. dactylifera SSR sex-related loci to eight other species within the genus. Phylogenetic analysis of a date palm sex-linked PdMYB1 gene in these species has revealed that sex-linked alleles have not clustered in a species-dependent way but rather in X and Y-allele clusters. Our data show that sex chromosomes evolved from a common autosomal origin before the diversification of the extant dioecious species.

Understanding the driving forces and molecular processes underlying dioecy and sex chromosome evolution, leading from hermaphroditism to the occurrence of male and female individuals, is of considerable interest in fundamental and applied research. The genus Phoenix, belonging to the family Arecaceae, consists of only dioecious species. Phylogenetic data suggests that the genus Phoenix diverged from a hermaphroditic ancestor shared with its closest relatives. Here we investigated the evolution of suppressed recombination within the genus Phoenix as a whole by extending the analysis of P. dactylifera sex-related loci to eight other species within the genus. We also performed a phylogenetic analysis of a date palm sex-linked PdMYB1 gene in these species. We found that X and Y sex-linked alleles clustered in a species-independent fashion. Our data show that sex chromosomes evolved before the diversification of the extant dioecious species. Furthermore, the distribution of Y haplotypes revealed two male ancestral paternal lineages which may have emerged prior to speciation.

AGAP : équipe Génomique évolutive et gestion des populations (GE²pop); BACKGROUND AND AIMS: Date palms (Phoenix dactylifera, Arecaceae) are of great economic and ecological value to the oasis agriculture of arid and semi-arid areas. However, despite the availability of a large date palm germplasm spreading from the Atlantic shores to Southern Asia, improvement of the species is being hampered by a lack of information on global genetic diversity and population structure. In order to contribute to the varietal improvement of date palms and to provide new insights on the influence of geographic origins and human activity on the genetic structure of the date palm, this study analysed the diversity of the species. METHODS: Genetic diversity levels and population genetic structure were investigated through the genotyping of a collection of 295 date palm accessions ranging from Mauritania to Pakistan using a set of 18 simple sequence repeat (SSR) markers and a plastid minisatellite. KEY RESULTS: Using a Bayesian clustering approach, the date palm genotypes can be structured into two different gene pools: the first, termed the Eastern pool, consists of accessions from Asia and Djibouti, whilst the second, termed the Western pool, consists of accessions from Africa. These results confirm the existence of two ancient gene pools that have contributed to the current date palm diversity. The presence of admixed genotypes is also noted, which points at gene flows between eastern and western origins, mostly from east to west, following a human-mediated diffusion of the species. CONCLUSIONS: This study assesses the distribution and level of genetic diversity of accessible date palm resources, provides new insights on the geographic origins and genetic history of the cultivated component of this species, and confirms the existence of at least two domestication origins. Furthermore, the strong genetic structure clearly established here is a prerequisite for any breeding programme exploiting the effective polymorphism related to each gene pool.

• Background and Aims The purpose of this study was to investigate the basis of the optimal hydration status for cryopreservation of intermediate oily seeds using Citrus as a model. • Methods The relationships between equilibrium relative humidity (RH), seed water content, presence of freezable water as determined by DSC analysis, and germination percentage after immersion in liquid nitrogen (LN) were investigated in Citrus aurantifolia, C. grandis, C. madurensis and C. reticulata. The relationship between the lipid content of seeds and their unfrozen water content was also investigated. • Key Results Independent of their level of seed desiccation tolerance, the optimal desiccation RH for seed tolerance to LN exposure was 75–80 % in the four species studied. This optimal hydration status always coincided with that at which presence of frozen water could not be detected in seed tissues during the cooling/thawing process. The unfrozen water content of seeds was variable between species and negatively correlated to seed lipid content. Using the present data, those obtained previously in seven coffee species and those reported by other authors for five other species, a significant linear relationship was found between the lipid content and the unfrozen water content of seeds. • Conclusions This study provides additional evidence that intermediate oily seeds do not withstand the presence of freezable water in their tissues during the cooling/warming process. Moreover, it offers two important applied perspectives: (1) independent of their level of desiccation tolerance, testing germination of seeds of a given oily seed species after equilibration in 75–80 % RH at 25 °C and LN exposure, gives a rapid and reliable evaluation of the possibility of cryopreserving whole seeds of this given species; (2) it is now possible to calculate the interval of water contents in which non-orthodox oily seeds of a given species are likely to withstand LN exposure as a function of their lipid content.

Large differences in seed desiccation sensitivity have been observed previously among ten coffee species (Coffea arabica, C. brevipes, C. canephora, C. eugenioides, C. humilis, C. liberica, C. pocsii, C. pseudo-zanguebariae, C. sessiliflora and C.stenophylla). Of these species,C. libericaandC. humiliswere the most sensitive to desiccation andC. pseudozanguebariaethe most tolerant. A study was carried out using the same seed lots to investigate if these differences in desiccation tolerance could be correlated with differences in soluble sugar content. Soluble sugars were extracted from dry seeds and analysed using high performance liquid chromatography. The seed monosaccharide (glucose and fructose) content was very low (1.5 to 2 mg g-1dry weight [dw]) in all species studied. The sucrose content ranged from 33 mg g-1dw inC. libericaseeds to 89 mg g-1dw in seeds ofC. pocsii. Raffinose was detected in the seeds of only five species (C.arabica, C.brevipes, C.humilis, C.sessiliflora, C.stenophylla), among which only three species (C.arabica, C.sessilifloraandC.brevipes) also contained stachyose. Both raffinose and stachyose were present in very low quantities (0.3–1.4 mg g-1dw and 0.1–0.7 mg g-1dw, respectively). Verbascose was never detected. No significant relationship was found between seed desiccation sensitivity and: (i) the sugar content; (ii) the presence/absence of oligosaccharides; and (iii) the oligosaccharide:sucrose ratio.

A broad variability for seed desiccation sensitivity, as quantified by the water content and the water activity at which half of the initial viability is lost, has been previously observed within nine African coffee species. In order to investigate if these different degrees of desiccation sensitivity correspond to an adaptive trait, additional data, such as the duration of seed development and seed water content at maturity, were measured for these species, and the relationships between these parameters and some climatic characteristics of their specific native environments were investigated. Since flowering in all coffee species occurs only a few days after the main rainfall marking the end of the dry season, simulations could be made, based on the continuous sequences of rainfall data compiled in databases of nine climatic stations, chosen for their appropriate location in the collecting areas. The simulations revealed a highly significant correlation between the duration of seed development and that of the wet season. Consequently, mature seeds are shed at the beginning of the following dry season. Moreover, the mean number of dry months that seeds have to withstand after shedding was significantly correlated with the parameters used to quantify seed desiccation sensitivity. By contrast, seed moisture content at maturity was not correlated with the level of seed desiccation tolerance. All these results are discussed on the basis of more detailed descriptions of the natural habitats of the coffee species studied.

Seed desiccation sensitivity was studied in nine species of the genus Coffeaby measuring seed viability after equilibration over various saturated salt solutions. A quantal response model based on the logistic distribution was developed in order to describe the typical S-shaped patterns observed. The closeness of fit of the desiccation sensitivity model was shown, and the assumption that seed desiccation sensitivity follows a continuous distribution within species was verified. For each species, the water content at which 50% of initial viability was reached, WC50, and a specific parameter describing the intra-specific variability, β, were calculated using a non-linear regression. A simplified water sorption model was developed which allowed easy calculation of water activity and water potential corresponding to WC50 (aw50 and Ψ50) for relative humidities ranging between 10 and 100%. Distribution of WC50and Ψ50 (or aw50) in the genus Coffea was homogeneous within the following intervals: from 0.05 to 0.38 g H2O.g−1dw for WC50 and from −168 to −11 MPa for Ψ50. Different classifications of the coffee species studied as regards to their desiccation sensitivity were obtained depending on whether WC50 or Ψ50was used for classification. The continuum for desiccation sensitivity observed within the nine species studied confirmed that coffee is an appropriate material for studying desiccation sensitivity.

Whether sex chromosomes are differentiated is an important aspect of our knowledge of dioecious plants, such as date palm (Phoenix dactylifera). In this crop plant, the female individuals produce dates, and are thus the more valuable sex. However, there is no way to identify the sex of date palm plants before reproductive age, and the sex-determining mechanism is still unclear. To identify sex-linked microsatellite markers, we surveyed a set of 52 male and 55 female genotypes representing the geographical diversity of the species. We found three genetically linked loci that are heterozygous only in males. Male-specific alleles allowed us to identify the gender in 100% of individuals. These results confirm the existence of an XY chromosomal system with a nonrecombining XY-like region in the date palm genome. The distribution of Y haplotypes in western and eastern haplogroups allowed us to trace two male ancestral paternal lineages that account for all known Y diversity in date palm. The very low diversity associated with Y haplotypes is consistent with clonal paternal transmission of a nonrecombining male-determining region. Our results establish the date palm as a biological model with one of the most ancient sex chromosomes in flowering plants.

In the present study, the efficiency of two cryopreservation strategies for oil palm (Elaeis guineensis Jacq.) was compared. If extracted from rehydrated kernels, 65% of the embryos desiccated to around 0.3 g H2O/g DW developed into plantlets after cryopreservation. In contrast, only 25% of embryos (0.12 g H2O/g DW) extracted from cryopreserved dry kernels developed into plantlets. However, this value was increased to 63% if kernels were partially rehydrated before freezing until the water content of embryos reached 0.3 g H2O/g DW. This study emphasizes the importance of partial rehydration of oil palm embryos before cryopreservation.

La cytométrie en flux a été utilisée pour estimer la quantité d'ADN nucléaire chez 13 espèces de #Coffea$ (Rubiacea) originaires d'Afrique. Douze espèces diploïdes (#2n$=22) et l'espèce tétraploïde #C. arabica$ (#2n$=44) ont été analysées. Pour 77 génotypes, des populations de noyaux isolés ont été colorées par l'iodure de propidium (IP ; non spécifique des bases). Pour trente neuf génotypes, le 4',6-diamidino-2-phenylindole (DAPI; AT spécifique) a été également utilisé. Les quantités 2C d'ADN nucléaire, estimées avec l'IP, oscillent entre 0,95 et 1,78 pg. Trois groupes correspondant à des quantités croissantes d'ADN ont été mis en évidence. Les trois espèces #C. sessiliflora, C. racemosa$ et #C. pseudozanguebariae$ se classent dans le groupe des plus petites valeurs (groupe 1 : 0,90 à 1,30 pg). Les trois espèces #C. eugenioides, C. stenophylla$ et #C.$ sp. F. se rangent uniquement dans le groupe des valeurs intermédiaires (groupe 2 : 1,31 à 1,60 pg). Les autres espèces se répartissent entre le groupe 2 et le groupe des plus hautes valeurs (groupe 3 : 1,61 à 1,80 pg). Les valeurs déterminées pour les espèces de #Coffea$, sont comparées aux niveaux intra- et inter-spécifique à celles d'autres angiospermes. Les différences observées sont discutées en fonction de l'origine éco-géographique des espèces, leurs caractéristiques phénologiques et la fertilité de leurs hybrides F1 interspécifiques. (Résumé d'auteur)

During a 7-day conditioning treatment of clumps of oil palm (Elaeis guineensis Jacq.) somatic embryos on a medium containing 0.75 M sucrose, the fructose and glucose concentrations remained constant, whereas a ten-fold and twenty-fold increase were noted for sucrose and starch concentrations, respectively. The only new sugar detected was arabinose which remained at a low concentration. After conditioning on media supplemented with various sugars and polyols at similar osmolarities, recovery of clumps of embryo growth was satisfactory except with ribose. After an additional desiccation period, survival was optimal with fructose, galactose, sucrose and glucose, intermediate with maltose and lower with other compounds. When embryos were cryopreserved without previous desiccation, survival was noted after conditioning treatment with sucrose only. In contrast, when freezing was performed after dehydration, survival could be obtained with several substances. It was optimal with sucrose, fructose, galactose and raffinose but was possible also with sorbitol and glucose. Intensity of recovery of proliferation was highest with embryos conditioned with sucrose.

Background and Aims Molecular phylogenetic studies of palms (Arecaceae) have not yet provided a fully resolved phylogeny of the family. There is a need to increase the current set of markers to resolve difficult groups such as the Neotropical subtribe Bactridinae (Arecoideae: Cocoseae). We propose the use of two single-copy nuclear genes as valuable tools for palm phylogenetics. Methods New primers were developed for the amplification of the AGAMOUS 1 (AG1) and PHYTOCHROME B (PHYB) genes. For the AGAMOUS gene, the paralogue 1 of Elaeis guineensis (EgAG1) was targeted. The region amplified contained coding sequences between the MIKC K and C MADS-box domains. For the PHYB gene, exon 1 (partial sequence) was first amplified in palm species using published degenerate primers for Poaceae, and then specific palm primers were designed. The two gene portions were sequenced in 22 species of palms representing all genera of Bactridinae, with emphasis on Astrocaryum and Hexopetion, the status of the latter genus still being debated. Key Results The new primers designed allow consistent amplification and high-quality sequencing within the palm family. The two loci studied produced more variability than chloroplast loci and equally or less variability than PRK, RPBII and ITS nuclear markers. The phylogenetic structure obtained with AG1 and PHYB genes provides new insights into intergeneric relationships within the Bactridinae and the intrageneric structure of Astrocaryum. The Hexopetion clade was recovered as monophyletic with both markers and was weakly supported as sister to Astrocaryum sensu stricto in the combined analysis. The rare Astrocaryum minus formed a species complex with Astrocaryum gynacanthum. Moreover, both AG1 and PHYB contain a microsatellite that could have further uses in species delimitation and population genetics. Conclusions AG1 and PHYB provide additional phylogenetic information within the palm family, and should prove useful in combination with other genes to improve the resolution of palm phylogenies.

International audience; † Background and Aims: Phoenix dactylifera (date palm) is a dioecious species displaying strong dimorphism between pistillate and staminate flowers. The mechanisms involved in the development of unisexual flowers are as yet unknown. † Methods: This paper describes the results of inflorescence and flower development studies using different histological and molecular cytological approaches. Nuclear integrity and cell division patterns in reproductive organs were investigated through DAPI staining and in situ hybridization using a histone H4 gene probe. † Key Results: The earliest sex-related difference in flower buds is observed at an otherwise ‘bisexual’ stage, at which the number of cells in the gynoecium of pistillate flowers is higher than in their staminate counterparts. In the pistillate flower, staminodes (sterile stamens) display precocious arrest of development followed by cell differentiation. In the staminate flower, pistillodes (sterile gynoecium) undergo some degree of differentiation and their development ceases shortly after the ovule has been initiated. Staminode and pistillode cells exhibit nuclear integrity although they did not show any accumulation of histone H4 gene transcripts. †Conclusions: These results strongly suggest that the developmental arrest of sterile sex organs and the subsequent unisexuality of date palm flowers result from a cessation of cell division and precocious cell differentiation rather than from cell death.

Oil palm (Elaeis guineensis Jacq.) somatic embryos differ from zygotic embryos in that they accumulate only small amounts of storage proteins. We compared the balance between deposition and degradation of storage proteins during zygotic or somatic embryogenesis and germinative growth in the two types of embryos. During mid to late zygotic embryogenesis, storage proteins accumulated and globulin 7S (GLO7A) gene transcripts were detected, whereas neither protease activity nor cysteine proteinase (CPR) gene transcripts were detected. Globulin degradation occurred after 8 days of in vitro germination in zygotic embryos and was accompanied by a decrease in GLO7A transcripts. Transcripts of three cysteine proteinase genes of the papain family were detected as early as Day 2 of in vitro germination. Several proteolytically active protein bands were identified by zymography, and CPR-like proteins were detected with an antibody raised against the Vicia sativa L. cysteine proteinase CPR1. Protease activities and CPR-like proteins were observed from Day 8 onward when globulin degradation occurred. During somatic embryogenesis and subsequent germinative growth, only small amounts of storage proteins accumulated, even though GLO7A transcripts were detected. Two of the three cysteine proteinase genes were expressed throughout both somatic embryogenesis and germinative growth. Protease activities and CPR-like protein species were detected in somatic embryos at several developmental stages. In contrast to zygotic embryogenesis, the accumulation of globulins and their subsequent mobilization appear to be concomitant processes during somatic embryogenesis, which could explain the low accumulation of storage proteins in somatic embryos.

Chlorogenic acid (5-CQA) is one of the major soluble phenolic compounds that is accumulated in coffee green beans. With other hydroxycinnamoyl quinic acids (HQAs), this compound is accumulated in particular in green beans of the cultivated species Coffea canephora. Recent work has indicated that the biosynthesis of 5-CQA can be catalyzed by a cytochrome P450 enzyme, CYP98A3 from Arabidopsis. Two full-length cDNA clones (CYP98A35 and CYP98A36) that encode putative p-coumaroylester 3'-hydroxylases (C3'H) were isolated from C. canephora cDNA libraries. Recombinant protein expression in yeast showed that both metabolized p-coumaroyl shikimate at similar rates, but that only one hydroxylates the chlorogenic acid precursor p-coumaroyl quinate. CYP98A35 appears to be the first C3'H capable of metabolising p-coumaroyl quinate and p-coumaroyl shikimate with the same efficiency. We studied the expression patterns of both genes on 4-month old C. canephora plants and found higher transcript levels in young and in highly vascularized organs for both genes. Gene expression and HQA content seemed to be correlated in these organs. Histolocalization and immunolocalization studies revealed similar tissue localization for caffeoyl quinic acids and p-coumaroylester 3'-hydroxylases. The results indicated that HQA biosynthesis and accumulation occurred mainly in the shoot tip and in the phloem of the vascular bundles. The lack of correlation between gene expression and HQA content observed in some organs is discussed in terms of transport and accumulation mechanisms.

Two hypotheses, namely the occurrence of post-thaw oxidative stress or imbibitional damage, were tested to explain the high sensitivity of coffee seeds to liquid nitrogen (LN) exposure. Oxidative stress was studied by measuring primary and secondary products of lipid peroxidation in seeds during the desiccation and rehydration periods. The 4-hydroxynonenal (4-HNE) content of seeds remained constant throughout the desiccation step. No significant difference was observed between desiccated seeds and seeds desiccated and exposed to LN for the evolution of their 4-HNE and hydroperoxide contents during rehydration. In both cases, an increase in 4-HNE and hydroperoxide contents of seeds was observed during the first hours of culture under germination conditions, followed by a progressive decrease down to values comparable to those observed in desiccated seeds. The hydroperoxide composition of frozen seeds was not significantly different from that of control seeds. The (S)/(R) enantiomeric ratios of 9- and 13-hydroxy-octadecadienoic acid extracted from rehydrating seeds were chiral, suggesting that they originated from lipoxygenase activity. These results suggest that the high sensitivity of coffee seeds to LN exposure is not directly associated with the occurrence of an oxidative stress during post-thaw rehydration. The effect on seed viability of different rehydration procedures previously identified to reduce membrane imbibitional injury was studied after desiccation and LN exposure. Desiccation tolerance increased with, by increasing order, seed osmoconditioning, pre-heating and prehumidifying prior to their culture under germination conditions. Among the four combinations of pre-humidification durations (24 or 48 h) and temperatures (25 or 37 � C) tested, pre-humidification for 24 h at 37 � C gave the highest level of desiccation tolerance. This rehydration procedure also dramatically increased seed viability after LN exposure. Seed desiccation sensitivity modelling in combination with the calculation of the decrease in seed water activity during cooling facilitated the explanation of the beneficial effect of controlled rehydration after desiccation and LN exposure. These results support the hypothesis that imbibitional membrane damage is involved in the sensitivity of coffee seeds to LN exposure.

Relationships between desiccation tolerance and dry matter, water and sugar contents were studied throughout the development of oil palm (Elaeis guineensis Jacq.) zygotic embryos and in immature embryos cultured on a sucrose-enriched medium. Embryo dry weight during in planta development increased between 80 and 140 d after pollination (DAP) and was then stable until maturity. Embryos underwent dehydration until 120 DAP, but their moisture content remained high at maturity (c. 2 g H2O g-1 DW). Desiccation tolerance was acquired between 83 and 104 DAP, and was positively correlated with embryo age and dry weight, and negatively correlated with initial water content during this period. Sucrose, the main soluble sugar present throughout embryo development, accounted for an average of 24% of the dry weight. Glucose and fructose contents decreased to less than 1 mg g-1 DW in embryos at maturity. At 117 DAP, as embryos became tolerant to desiccation, the monosaccharides/sucrose ratio fell to 0.015 and raffinose was detected. Stachyose appeared later in 147-day-old embryos and accumulated until shedding. In vitro culture of immature embryos in the presence of high sucrose concentrations (350 and 700 mM) resulted in an increase in their dry weight and a decrease in their water content, and induced the acquisition of desiccation tolerance. Under these conditions, sucrose accumulated in embryos to 30–40% on a dry weight basis, but neither raffinose nor stachyose was detected. Acquisition of desiccation tolerance by oil palm immature embryos was associated both in planta and in vitro with an accumulation of dry matter, a reduction of moisture content, and a fall in the monosaccharides/sucrose ratio. In planta, survival to dehydration was also related with the deposition of oligosaccharides whereas in vitro, it was related with high sucrose accumulation. The role of sugars in the acquisition of desiccation tolerance in oil palm embryos is discussed.

Osmoconditioning-controlled rehydration of seeds in a solution with low osmotic potential -has been shown to reinvigorate aged seeds. The present work aimed at investigating the effect of osmoconditioning on the germination of cryopreserved seeds of Coffea arabica, whose viability and vigour are drastically affected by cryopreservation. For cryopreservation, seeds were desiccated to 0.21 g H2O/g dw, cooled at 1 degree C/min to -50 degree C, then immersed rapidly in liquid nitrogen. After rapid rewarming, seeds were osmoconditioned for 1 to 6 weeks using solutions with osmotic potentials between -1 and -4 MPa. The time to produce half of the final percentage of normal seedlings, T50, was about three fold lower with osmoconditioned seeds than with non-osmoconditioned seeds (12-14 d vs 36 d). Moreover, after a 6-week osmoconditioning treatment with solutions with osmotic potential of -1 and -1.25 MPa, the percentage of seedlings recovered from cryopreserved seeds was 64-74%, against 13-16% only for cryopreserved seeds which were not osmoconditioned.

L'effet de l'acide abscissique (ABA) sur la tolérance à la dessiccation des embryons somatiques de palmier à huile, leur contenu en sucres solubles et leur taux de germination a été étudié. L'ABA a été ajouté pendant le développement ou la germination des embryons somatiques. L'ABA n'a pas d'effet significatif sur le poids sec, la teneur en eau et en saccharose des embryons. En revanche, les teneurs en monosaccharides sont diminuées dans les embryons traités à l'ABA et le raffinose est détecté dans des embryons traités pendant 6 semaines avec des concentrations croissantes en ABA (de 5 à 25 microM). L'ABA améliore la tolérance des embryons à la dessiccation rapide. Les embryons traités avec 25 microM d'ABA ont un taux de survie supérieur à celui des embryons témoins. Le traitement des embryons avec 25 microM d'ABA provoque un retard dans l'émission des pousses feuillées par rapport aux témoins lors de la germination sur milieu sans hormone. En revanche, aucune germination n'est observée pour les embryons traités avec 50 microM d'ABA. La présence d'ABA dans le milieu de germination des embryons provoque l'inhibition de l'émission des pousses feuillées. Ces résultats suggèrent un rôle de l'ABA dans la maturation et la tolérance à la dessiccation des embryons somatiques de palmier à huile.

The effect of exposure to ultra-low temperature (liquid nitrogen, LN) on viability of seeds desiccated to various water contents was investigated in 9 coffee species. Three groups of species could be distinguished based on seed survival after LN exposure. In group 1 species, no seedling production could be obtained after LN exposure due to endosperm injury. In group 2 species, recovery was very low or nil after rapid cooling, and only moderate after slow cooling. In group 3 species, very high percentages of seedling development were observed after both rapid and slow cooling. A high interspecific variability for the high moisture freezing limit was observed within the species of groups 2 and 3, since it ranged from 0.14 to 0.26 g H2O g-1 dry weight. A very highly significant correlation was found for those species between the unfreezable water content, as determined from DSC analysis, and the high moisture freezing limit of their seeds. No significant correlation was found between seed lipid content, which varied from 9.8 to 34.6% dry weight, and survival after LN exposure. However, a negative relationship was found between seed unfreezable water content and lipid content. Interspecific differences in fatty acid composition of seed lipids resulted in a high variability in the percentage of unsaturated fatty acids, which ranged from 28.7 to 54.4% among the 9 species studied. For all species studied, a highly significant correlation was found between the percentage of unsaturated fatty acids and the percentage of seedling recovery after rapid or slow cooling.

In the range of water contents studied (0.1–0.4 g H2O g dw−1),Coffea arabicaseeds were less sensitive to desiccation thanC. costatifructa, C. racemosaandC. sessilifloraseeds. At 0.20 g H2O g dw−1, 53% ofC. arabicaseeds germinated after direct immersion in LN (rapid cooling, 200°C min−1), but none of them developed into normal seedlings. By contrast, inC. costatifructa, C. racemosaandC. sessiliflora, when seeds were dehydrated to the optimal water content (0.19, 0.28 and 0.31 g H2O g dw−1, respectively), the percentages of seeds which developed into normal seedlings after LN exposure were 26, 78 and 31% of the desiccation control, respectively. Normal seedlings could be recovered from cryopreservedC. arabicaseeds only if they were desiccated to 0.20 g H2O g dw−1and precooled slowly to −50°C prior to immersion in LN. Precooling seeds at 2°C min−1allowed 25% of seeds to develop into normal seedlings. The thawing rate had no effect on the survival of cryopreservedC. arabicaseeds. In all cryopreservation experiments, the total germination did not reflect the percentage of seeds which developed into normal seedlings. Examination of excised embryos indicated a partial explanation of this difference since only the shoot apex was destroyed in abnormal embryos, whereas the hypocotyl and radicle were normal.

The standard cryopreservation process previously developed for oil palm clones using shiny white, finger-like somatic embryos could be applied in some cases to standard cultures. Its efficiency was markedly improved by completing the 7-day pregrowth period on 0.75 M sucrose by an additional dehydration period carried out either by placing the embryos in the air current of the laminar flow cabinet or in an air tight box containing silica gel. This improved process was successfully applied to 7 different clones. It will facilitate the routine uof cryopreservation for oil palm cultures.

Phenylalanine ammonia lyase (PAL) is the first entry enzyme of the phenylpropanoid pathway producing phenolics, widespread constituents of plant foods and beverages, including chlorogenic acids, polyphenols found at remarkably high levels in the coffee bean and long recognized as powerful antioxidants. To date, whereas PAL is generally encoded by a small gene family, only one gene has been characterized in Coffea canephora (CcPAL1), an economically important species of cultivated coffee. In this study, a molecular- and bioinformatic-based search for CcPAL1 paralogues resulted successfully in identifying two additional genes, CcPAL2 and CcPAL3, presenting similar genomic structures and encoding proteins with close sequences. Genetic mapping helped position each gene in three different coffee linkage groups, CcPAL2 in particular, located in a coffee genome linkage group (F) which is syntenic to a region of Tomato Chromosome 9 containing a PAL gene. These results, combined with a phylogenetic study, strongly suggest that CcPAL2 may be the ancestral gene of C. canephora. A quantitative gene expression analysis was also conducted in coffee tissues, showing that all genes are transcriptionally active, but they present distinct expression levels and patterns. We discovered that CcPAL2 transcripts appeared predominantly in flower, fruit pericarp and vegetative/lignifying tissues like roots and branches, whereas CcPAL1 and CcPAL3 were highly expressed in immature fruit. This is the first comprehensive study dedicated to PAL gene family characterization in coffee, allowing us to advance functional studies which are indispensable to learning to decipher what role this family plays in channeling the metabolism of coffee phenylpropanoids. Electronic supplementary material The online version of this article (doi:10.1007/s00425-012-1613-2) contains supplementary material, which is available to authorized users.