Primer sets were developed from 85 Coffea arabica sequences in addition to 25 already published primer sets. They were subsequently used for amplification in six African Coffea species: Coffea canephora (CAN), Coffea eugenioides (EUG), Coffea heterocalyx (HET), Coffea liberica (LIB), Coffea sp. Moloundou (MOL) and Coffea pseudozanguebariae (PSE). The amplification percentages for these 110 primer pairs ranged from 72.7% for LIB to 86.4% for PSE. Good transferability was thus obtained within the Coffea genus. When focusing on the two species CAN and PSE, high genetic diversity, high polymorphic locus rates (above 80%) and a mean allele number per polymorphic locus of more than 3 were noted. The estimated null allele percentage was -11% for PSE and -9% for CAN. Sixty three percent (CAN) and 79.5% (PSE) of the fixation index (Fis) values were positive. The within-species polymorphism information content (PIC) distribution showed two modes for both species. Although the two species shared 30 polymorphic loci, no correlation between CAN and PSE PIC values was obtained. All of these data are discussed in relation to the polymorphism level and the potential use of these SSRs for subsequent analysis of genetic diversity or genetic mapping.

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In contrast to desiccation-tolerant ‘orthodox’ seeds, so-called ‘intermediate’ seeds cannot survive complete drying and are short-lived. All species of the genus Coffea produce intermediate seeds, but they show a considerable variability in seed desiccation tolerance (DT), which may help to decipher the molecular basis of seed DT in plants. We performed a comparative transcriptome analysis of developing seeds in three coffee species with contrasting desiccation tolerance. Seeds of all species shared a major transcriptional switch during late maturation that governs a general slow-down of metabolism. However, numerous key stress-related genes, including those coding for the late embryogenesis abundant protein EM6 and the osmosensitive calcium channel ERD4, were up-regulated during DT acquisition in the two species with high seed DT, C. arabica and C. eugenioides. By contrast, we detected up-regulation of numerous genes involved in the metabolism, transport, and perception of auxin in C. canephora seeds with low DT. Moreover, species with high DT showed a stronger down-regulation of the mitochondrial machinery dedicated to the tricarboxylic acid cycle and oxidative phosphorylation. Accordingly, respiration measurements during seed dehydration demonstrated that intermediate seeds with the highest DT are better prepared to cease respiration and avoid oxidative stresses.

An interspecific cross (BC 1) involving a species with one of the largest genomes in the Coffea genus [ Coffea heterocalyx (HET), qDNA = 1.74 pg] and a species with a medium-sized genome [ Coffea canephora (CAN), qDNA = 1.43 pg] was studied using two types of molecular markers, AFLP and SSR. One hundred and eighty eight AFLP bands and 34 SSR primer pairs were suitable for mapping. The total map length was 1,360 cM with 190 loci distributed in 15 linkage groups. The results were compared to those obtained previously on an interspecific BC 1 progeny involving a species with a medium-sized genome ( Coffea liberica var dewevrei, DEW) and a species with one of the smallest genomes ( Coffea pseudozanguebariae, PSE). They are discussed relative to three main points: (1) the relevance of the different marker types, (2) the genomic distribution of AFLP and SSR markers, and (3) the relation between AFLP polymorphism and genome size.

Several abiotic factors influence the chemical composition of essential oils. Understanding these factors is an important step in developing quality products that meet market demands. This research work aims to study the chemical composition of the essential oils of ylang-ylang (Cananga odorata, forma genuina) according to the maturity of flowers. The volatile compounds of ylang-ylang flowers from Reunion Island were extracted by hydrodistillation and the samples were analyzed by high resolution gas chromatography coupled with mass spectrometry (GC-MS) allowing for the identification of 70 volatile compounds. The chemical composition of the essential oils extracted from the flowers at 5 different stages of development varies both qualitatively and quantitatively. The volatile compounds observed belong to 4 chemical groups which are esters, alcohols, terpenes, and ether-oxides. The synthesis of light oxygenated compounds is largely the predominant chemical subgroup in all stages of development. Their relative content is considerably increased during flower ripening with a peak concentration in stage 4 (SD4). The highest concentrations of non-terpene esters and heavy oxygenated compounds are found in stages 1 (SD1) and (SD5), respectively, while no chemical subgroup is dominant in the intermediate stages 2 (SD2) and (SD3). The dynamics of volatile compounds have also been studied. This study established that the stage of development of ylang-ylang flowers significantly influences the dynamics of volatile compounds in the extracted essential oils. Total oxygenated compounds that are highly odoriferous in essential oils increase progressively and significantly with flower maturity, unlike hydrocarbon terpenes, which are less valuable in terms of their contribution to the fragrance and following opposite kinetics; suggesting that odoriferous properties increase with the development of the flower, with a higher intensity at SD4.

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Anthracnose, caused by the fungus called Colletotrichum gloeosporioides, is the main postharvest disease that affects mango production on Reunion Island. Fruits for the export market are always treated with chemicals. The use of chemical treatment is not in adequation with consumer expectations, and the increasing emergence of fungicide-resistant isolates promotes the development of alternatives methods. The principal objective of this work was to use antimicrobial properties of thymol as an alternative postharvest treatment on mango. Thymol diluated in a penetrating agent solution was effective on mango anthracnose. At a concentration of 0.025%, Thymol limited necrosis development due to pathogens during fruit storage. This treatment can stimulate some of polyphenols biosynthesis involved in the fruit resistance to postharvest disease, particularly the synthesis of gallic acid and resorcinol. With this final concentration of 0.025% thymol, the treatment did not affect fruit maturation and quality, especially the peel colour and sugar content. Importantly, the treatment did not show any detectable effect on organoleptic qualities of the fruit.