Search

This research was funded by the Foundation for Science and Technology (FCT) UNIT (UID/AGR/04129/2020) of LEAF- -Linking Landscape, Environment, Agriculture and Food, Research Unit. info:eu-repo/semantics/publishedVersion

To elucidate the overall metabolism of sugars in coffee fruits, in situ metabolism of exogenously supplied 14C-glucose were investigated in segments of pericarps and seeds of two cultivars of Coffea arabica and C. canephora fruits obtained from different growth and ripening stages. The coffee fruits were categorized into five stages 1 to 5 which were corresponding to young, developing, mature (green), ripening (pink) and fully-ripened (red) fruits, respectively. The rates of uptake and metabolism of [U-14C]glucose in fruits of the stages 1‒3 was higher than in fruits of stages 4‒5. Release of 14CO2 which represented cellular respiration was high in both pericarp and seeds of C. arabica and C. canephora up to the stage 3, but it gradually reduced and the minimum was found in the fully ripened stage 5 fruits. The highest incorporation of radioactivity into the methanol-soluble metabolites was found in the stage 2 fruits. In pericarp, incorporation of radioactivity into the acidic component (mainly consisted of organic acids) was much higher than into basic component (mainly consisted free amino acids). In seeds, significant amounts of the radioactivity were found in the basic fractions especially at the stages 4 and 5. [U-14C]glucose was converted to fructose and sucrose in both pericarp and seeds. Only small rate of sucrose synthesis from [14C]glucose was detected 18 h after administration, however, its relative rate is slightly increased at stages 4-5 fruits. Incorporation of radioactivity into the methanol-insoluble metabolites (mainly consisted protein starch and cell wall constituents) was found in any stages of fruits. The maximum rates were found in pericarp and seeds of developing (stage 2) fruits of C. arabica and in those at early three stages 1‒3 of C. canephora. Possible metabolic routes and relative participation of carbon in different metabolite biosynthesis in coffee fruits are discussed., European Chemical Bulletin, Vol 4, No 4-6 (2015): European Chemical Bulletin

La génétique d'association et la sélection génomique sont devenues des méthodes importantes dans les programes d'amélioration de la reproduction des cultures pérennes, de manière à accélérer les efforts de reproduction et d'accroître l'efficacité de la sélection. Ce sont des bonnes alternatives à l'approche classique de cartographie par caractères quantitatives. Le programme de recherche d'amelioration du cacaoyer de l'USDA-ARS et Mars Inc. a permis le développement dans plusieurs pays de populations de cacaoyer sélectionnées pour leurs gènes de résistance au balai de sorcière, à la moniliose et à la pourriture brune des cabosses, mais également pour leurs caractères de productivité. Les QTL associés à ces traits ont été identifié; Cependant, certaines de ces associations sont spécifiques à certaines populations et sont influencées par leurs interactions avec l'environnement De plus, la majorité de ces caractères sont contrôlées par plusieurs gènes à effets réduits. En raison de ces contraintes, les méthodes de sélection assistées par marqueur (MAS) et les méthodes de reproduction traditionnelle n'ont pas été très efficaces dans l'accélération du développement des variétés de cacaoyer à meilleurs rendements, diférentes saveurs et à l'augmentation de la résistance contre les maladies et les insectes. Les progrès technologiques et du séquençage génomique ainsi que la réduction des coûts associés, ont permis le développement de milliers de marqueurs "Single Nucleotide Polymorphism (SNP)" qui sont actuellement utilisés lors de l'identification parentale, la caractérisation du matériel génétique et la cartographie fine des QTL. En outre, l'approche dite "genotype-by-sequencing" est également actuellement utilisée chez le cacaoyer. Enfin, le récent développement de méthodologies statistiques robustes pour la génétique d'asation et la sélection génomique (GS) les rendent très attrayantes pour une utilisation dans l'amélioration du cacaoyer. Nous utilisons actuellement dans notre programme de recherche les QTL identifiés précédemment et appliquons des techniques de génétique d'association afin d'évaluer les associations marqueur-caractère dans différentes populations de cacaoyer d'Amérique du Sud et Centrale, d'Afrique et d'Asie. Un autre objectif est l'identification de loci signi:ficativement asés à la résistance contre les maladies, aux caractères agronomiques et caractères de qualités, afin de pouvoir ensuite les utilisés comme prédicateurs de performance. La sélection basée sur ces prédicateurs peut mener plus rapidement à des gains génétiques, à une diminution du temps et du coût de libération de variétés supérieures à haut rendement, résistantes aux maladies et présentant les attributs de qualité exigés par l'industrie de la confiserie.

Coffee is the most traded crop by Southern countries and is the main source of income for more than 75 millions small farmers all over the world. Despite its economical importance and the obvious necessity to improve the crop in order to respond to new environmental constraints and to the consumer demand for quality, the sequencing of its genome only started in late 2009. An international consortium was formed, led by Genoscope, to perform this task. Coffea canephora, a diploid cultivated species, was chosen, since C. arabica is tetraploid. Furthermore, IRD developed a double haploid plant because C. canephora is allogamous. Its genome size is about 695 Mb and whole genome sequencing is being performed using NGS complemented by BAC ends coming from two BAC libraries covering in total 14.8 genome equivalents. SSR markers mined from these sequences are being mapped to establish a consensus genetic map based on the map kindly provided by Nestlé and ICCRI. Both Roche pyrosequencing (454) and Illumina technology are used to provide a 20x coverage by 454 and 50x by Illumina. Direct and paired end sequencing are underway, two, 8kb and 20kb insert libraries have been constructed. In addition to the publicly available EST, more transcriptome sequencing is also planned using 454 to facilitate the annotation. The Coffea genome will be one of the first Asterid genome to be sequenced providing information on the proposed ancestral eudicot genome hexaploidization and for comparative genomics among angiosperms. It will also provide information to breeders for relating QTLs to genes. (Texte d'intégral)

Commercial coffee production relies mainly on two closely related species: Coffea arabica and C. canephora, which account respectively for 70 and 30% of the coffee production. All coffee species are diploid (2n=2x=22) and generally selfincompatible, except for C. arabica which is the only tetraploid (2n=4x=44) and self-fertile. Molecular analyses (Lashermes et al. 1999) have indicated that C. arabica is a recent allotetraploid (CE genome) formed by hybridisation between two related diploid species: C. canephora (C genome) and C. eugenioides (E genome). In spite of the close relationship between the two constitutive sub-genomes, C. arabica displays diploid-like meiotic behavior with bivalent formation (Krug and Mendes 1940, Lashermes et al. 2000). The genomes of coffee species (Cros et al. 1995; Noirot et al. 2003) appear to be of rather low size (i. e. about 660, 710 and 1300 Mb for C. eugenioides, C. canephora and C. arabica, respectively). Several institutes are combining their scientific resources and expertise to sequence, assemble, and annotate the entire genome of C. canephora. The C. canephora genome consists of 11 chromosomes, is about 710 Mb in size, and is being sequenced de novo with deep coverage using 454 paired-end and single reads, and 50x coverage with Illumina GAIIx data to obtain a reference genome for Coffea. The overall sequencing strategy as well as progress of the project will be described.

Coffee, tea, and chocolate converge Caffeine has evolved multiple times among plant species, but no one knows whether these events involved similar genes. Denoeud et al. sequenced the Coffea canephora (coffee) genome and identified a conserved gene order (see the Perspective by Zamir). Although this species underwent fewer genome duplications than related species, the relevant caffeine genes experienced tandem duplications that expanded their numbers within this species. Scientists have seen similar but independent expansions in distantly related species of tea and cacao, suggesting that caffeine might have played an adaptive role in coffee evolution. Science , this issue p. 1181 ; see also p. 1124