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RATIONALE - Arabusta coffee was created by crossing Coffea arabica L. and C. canephora Pierre ex-Froehner after doubling the chromosome number of C. canephora. For breeding studies and coffee quality improvement, clones have been planted in French Guiana. As green bean metabolite content largely influences the coffee cup quality, biochemical and sensory analyses of Robusta and Arabusta were done on green beans and compared as part of Breedcafs H2020 project. METHODS - Arabusta cherries were harvested on 6 clones in 4 farms in Apatou and in Combi research station, and those from Robusta in Combi research station. They were wet processed before grinding. Phenolic compounds and alkaloids were quantified by HPLC (Campa et al, 2017), sucrose by enzymatic analysis (Megazyme kit, Ireland), diterpenes by NMR (Portaluri et al, 2020) and VOC by headspace SPME-GC/ MS (Marie et al, 2020). Lipids were extracted (Folch et al, 1957) and quantified by cgfb (Bordeaux). Sensory analyses followed the protocol guidelines of the Specialty Coffee Association (SCA) for C. arabica (Marie et al, 2020).We used Statistica software for analyses. RESULTS - Compared to Robusta, Arabusta had a lower caffeine content and higher trigonelline, sucrose and fatty acid contents. Arabusta evidenced both 16-O-methylcafestol and kahweol, known markers for Robusta and Arabica species, respectively. 17 of the 25 non-volatile and 23 of the 47 volatile compounds showed significant differences (p≤0.05) between Arabusta and Robusta. Except 5-caffeoylquinate and coumaroylquinate, chlorogenic acids accumulated more in Robusta. A PCA based on volatile compound content separated samples in three groups: Robusta samples, most of the Arabusta from Apatou (richer in pyrazine, toluene, 2-propanone) and those from Combi associated with 3 from Apatou (richer in D-limonene, DMSO, methyl-butanoic acid, and IBMP). A sensory analysis based on 9 sensory parameters indicated that 3 samples received a final score higher than 80. A PCA confirmed that 2 Arabusta samples were particularly different from all the others. CONCLUSIONS & PERSPECTIVES - With higher contents in sucrose, trigonelline, diterpenes, fatty acids and D-limonene and a lower content in caffeine, the composition of the Arabusta green beans seems significantly different from Robusta. The sensory analysis supports the hypothesis that some Arabusta clones possess the potential to produce quality coffee. However, it is necessary to continue the research to confirm these results. This research was funded by BREEDCAFS project, supported by the European Commission under the Horizon 2020 – Research and Innovative Program, H2020-SFS-2016-2, grant agreement number: 727934.

RATIONALE - Arabusta coffee is an interspecific hybrid derived from C. arabica x C. canephora, often used in coffee breeding to study both the gene transfer from Robusta and its possible use in coffee production. The plants have very different morphological characteristics, as well as different levels of fruit production when compared with the parental species. Arabusta coffee was also studied from a sensory point of view, but in general the literature on this hybrid is rather scarce and the knowledge on it is still fragmentary. From a morphoanatomical point of view, as far as we know, no investigations have been devoted to study Arabusta seed morphology and to disclose possible Arabica-like or Robusta-like traits in its cell structure and this highly stimulated the present work. METHODS - Seed samples of C. arabica L. (Costarica, 2019), C. canephora Pierre ex-Froehner (French Guyana, 2019) and F1 clones of Arabusta coffee (French Guyana, end of 2018) were harvested, properly processed and selected. Seeds were kept in a fixative solution for several days, then rinsed in tap water and cut at -20°C with a cryostat (Leica CM1520). Seed sections of 60 μ in thickness were observed by a Scanning Electron Microscope (Hitachi TM3030plus). Sections of 12 μ in thickness were staining in a Toluidine Blue O solution to highlight the main cell components. Measurements of cell wall area were performed on the electronic images by a Leica Software (Las X). RESULTS ( Arabusta is characterized by an elongated seed, slightly rounded, generally with a linear furrow. The endosperm cells are regular, characterized by a polygonal shape, with not frequent nodes present in their cell wall. Cell wall thickness is not significantly different from the parental species (5,7 ± 1,6 μ). However, the area occupied by the cell wall respect to the cell total area (28%) is more close to that measured in Arabica seeds (29%) than that in Robusta seeds (43%). Optical microscopy observations furtherly put in evidence this tissue aspect, showing similar cell size in Arabusta and Arabica seeds, and smaller cells for Robusta coffee. This feature is probably related to ploidy level (Arabica and Arabusta : 2n = 4x = 44, Robusta 2n = 2x = 22). No histochemical differences in the cell content were observed among the examined coffee species under the chosen experimental conditions. CONCLUSIONS & PERSPECTIVES - The measurements performed on cell wall area and measured diameter as well as cell content area and endosperm cell size show that the morphoanatomical characteristics of Arabusta seeds corresponds more to those of Arabica than Robusta seeds. Further studies are necessary to confirm this preliminary view.

Conventional American cultivars of coffee are no longer adapted to global warming. Finding highly productive and stable cultivars in different environments without neglecting quality characteristics has become a priority for breeders. In this study, new Arabica F1 hybrids clones were compared to conventional American varieties in seven contrasting environments, for yield, rust incidence and volume of the canopy. The quality was assessed through size, weight of 100 beans, biochemical analysis (24 aroma precursors and 31 volatiles compounds) and sensory analysis. Conventional varieties were the least productive, producing 50% less than the best hybrid. The AMMI model analysis pointed out five hybrids as the most stable and productive. Two F1 hybrids clones, H1-Centroamericano and H16-Mundo Maya, were superior to the most planted American cultivar in Latin and Central America showing a high yield performance and stability performance. H1-Centroamerica and Starmaya contain more d-limonene than Caturra, while Starmaya contain more 3-methylbutanoic acid than the control. Those two latter volatiles compounds are linked with good cup quality in previous studies. In terms of sensory analysis, Starmaya and H1-Centroamericano scored better than control.

Conventional American cultivars of coffee are no longer adapted to global warming. Finding highly productive and stable cultivars in different environments without neglecting quality characteristics has become a priority for breeders. In this study, new Arabica F1 hybrids clones were compared to conventional American varieties in seven contrasting environments, for yield, rust incidence and volume of the canopy. The quality was assessed through size, weight of 100 beans, biochemical analysis (24 aroma precursors and 31 volatiles compounds) and sensory analysis. Conventional varieties were the least productive, producing 50% less than the best hybrid. The AMMI model analysis pointed out five hybrids as the most stable and productive. Two F1 hybrids clones, H1-Centroamericano and H16-Mundo Maya, were superior to the most planted American cultivar in Latin and Central America showing a high yield performance and stability performance. H1-Centroamerica and Starmaya contain more d-limonene than Caturra, while Starmaya contain more 3-methylbutanoic acid than the control. Those two latter volatiles compounds are linked with good cup quality in previous studies. In terms of sensory analysis, Starmaya and H1-Centroamericano scored better than control.

Frontiers in molecular biosciences 6, 29 (2019). doi:10.3389/fmolb.2019.00029, Published by Frontiers, Lausanne

RATIONALE Aromatic quality is a very important target for genetic improvement and breeding of Coffea arabica. For coffee geneticists, it is of paramount importance to set targets and breed for aromatic quality as expected by the coffee industry for the consumers. The objective of the study was to relate coffee industry quality demand to objective workable criteria for selection. METHODS We presented 60 random commercial samples to a panel made of professional cuppers from the industry for a Signal Detection sensorial analysis. Based on the results, we selected 12 samples representative of the diversity of quality evaluated by the panel. On this sub-sample, we ran i) a Lexicon sensorial analysis and ii) a SPME analysis of Volatile Compounds (VOC) on both green and roasted coffee. We then implemented several statistical analysis to relate the appreciation of the quality from the professional industry coffee cuppers to some objective quality attributes and specific VOCs. RESULTS After the Signal Detection sensorial Analysis, 3 consistant clusters were identified as: Super Specialty Quality Coffee, Specialty Coffee and Commercial Coffee. Lexicon analysis prove that Super Specialty had no negative flavor or aroma attributes and at least two faborable flavor or aroma attributes. Various VOCs appeared to be related to the Signal Detection Sensory Analysis. However, Limonene appeared to be the most discriminant one on green coffee. CONCLUSIONS & PERSPECTIVES To our knowledge, it is the first public study searching for objective Coffee Aromatic Quality based on a panel made of coffee industry professional cuppers. Limonene appeared to be a good proxy for market coffee aromatic quality measured on green coffee. This opens a strategy for Coffee Aromatic Quality genetic improvement based on the screening of candidates for the limonene content of green coffee. Searching for molecular markers related to Limonene will further speed up the genetic progress.

Figure showing quantification of azelaic acid by HPLC on C18 reverse phase column. Quantification of azelaic acid (PSA produced) by standard curve A&B. (PPTX 51 kb)

Coffee is the second largest traded commodity after oil and large amounts of by-products are generated in the coffee industry every year. In particular, coffee silverskin (CS) and spent coffee grounds (SCG) are the main coffee industry residues. CS is about 4.2% (w/w) of coffee beans and the valorisation of this waste through the biorefinery approach may boost the circular economy development. In the present contribution, CS was pretreated with one of the mainly investigated biomass pretreatment reported in literature: alkaline hydrolysis in NaOH solutions. After enzymatic hydrolysis of the pretreated CS, the obtained sugars were used as carbon source to produce butanol and isopropanol by Clostridium beijerinckii DSM 6423. Moreover, fermentation tests were also carried out with synthetic media to investigate the effects of the alkaline pretreatment on the fermentation process. When pretreated CS was used as feedstock, the largest yields were 0.16 and 0.31 gsolvent/gsugars isopropanol and butanol, respectively. The reported results foster further studies regarding the reuse of CS for solvents production through fermentation processes.

Figure showing Quantification of azelaic acid by LC-MS. LC-MS profile of standard azelaic acid and putative azelaic acid collected at RT 13 from HPLC (A). Quantification of isolated and purified azelaic acid by standard curve (B). In 5 μl of RT 13 sample injected, there is 0.476 μg of azelaic acid which can be translated to 19.992 μg/L. (PPTX 69 kb)

Figure showing validation of the RNAseq-based expression by gene promoter studies. Promoters of selected gene were fused with promoter probe vector pBBRGFP-Gm and tested with similar concentration of azelaic acid which was used in RNAseq expression studies. Significant fold change from selected genes was observed only between pBGFPgene 1818/methanol and pBGFPgene 1818/azelaic acid. Data shown are the mean and standard deviation of experiment performed thrice in triplicate. (PPTX 99 kb)

Table representing RNAseq expressed genes upon induction of azeliac acid. (DOCX 15 kb)

Table showing list of compounds identified by NIST library search of PSV metabolome cultured in M9 glucose medium. (DOCX 21 kb)

Table showing list of compounds identified by NIST library search of PSA metabolome cultured in M9 glucose medium. (DOCX 24 kb)

Table showing list of compounds identified by NIST library search of M9 glucose medium Control. (DOCX 25 kb)