SUMMARYGlycosides are an important potential source of aroma and flavour compounds for release as volatiles in flowers and fruit. The production of glycosides is catalysed by UDP-glycosyltransferases (UGTs) that mediate the transfer of an activated nucleotide sugar to acceptor aglycones. A screen of UGTs expressed in kiwifruit (Actinidia deliciosa) identified the gene AdGT4 which was highly expressed in floral tissues and whose expression increased during fruit ripening. Recombinant AdGT4 enzyme glycosylated a range of terpenes and primary alcohols found as glycosides in ripe kiwifruit. Two of the enzyme's preferred alcohol aglycones, hexanol and (Z)-hex-3-enol, contribute strongly to the 'grassy-green' aroma notes of ripe kiwifruit and other fruit including tomato and olive. Transient over-expression of AdGT4 in tobacco leaves showed that enzyme was able to glycosylate geraniol and octan-3-ol in planta whilst transient expression of an RNAi construct in Actinidia eriantha fruit reduced accumulation of a range of terpene glycosides. Stable over-expression of AdGT4 in transgenic petunia resulted in increased sequestration of hexanol and other alcohols in the flowers. Transgenic tomato fruit stably over-expressing AdGT4 showed changes in both the sequestration and release of a range of alcohols including 3-methylbutanol, hexanol and geraniol. Sequestration occurred at all stages of fruit ripening. Ripe fruit sequestering high levels of glycosides were identified as having a less intense, earthier aroma in a sensory trial. These results demonstrate the importance of UGTs in sequestering key volatile compounds in planta and suggest a future approach to enhancing aromas and flavours in flowers and during fruit ripening.

Robusta coffee (C. canephora) covers 36% of world coffee production and has strategic relevance as a beverage that it is produced by thousands of small-scale producers around the world. Although mainly grown in Africa and Asia as opposed to Latin America, this situation is changing. Colombia is recognized as a producer of high-quality Arabica (C. arabica L.) coffee, however we argue that Robusta represents a great economic opportunity for small scale producers, for the industrialization of new products and for emerging coffee chains. Therefore, the objective of this review is to outline the agronomic value of Robusta coffee as a “new crop” in Colombia. As background we compare the better-known Arabica to the Robusta coffees from a Latin American perspective. Robusta shows differences in geographical distribution, genetics, originating species, physiology and phenology. Robusta and Arabica also differ in their chemistry, sensory attributes, industrial use, segments of market and price. Despite the marked differences between the two coffees, the popularity and consumption of Robusta has been on the increase due to the expansion of markets in emerging economies and in developed markers for home espresso preparation where it is used in high quality coffee blends. Robusta is currently replacing areas of other coffees due to hotter temperatures to which it is adapted. Although Robusta is still new to Colombia, this species has potential adaptation in lowland areas considered “non-traditional” for Colombian coffee cultivation and as a valuable component of agro-ecological production systems. Robusta is a novel crop option for certain regions that is needed for the future of coffee in Latin America and for growth of coffee production and consumption in Colombia.