ORCID ID: 0000-0001-5417-5066 (Y.M.T.).Phenylpropanoid volatiles are responsible for the key tomato fruit (Solanum lycopersicum) aroma attribute termed "smoky." Release of these volatiles from their glycosylated precursors, rather than their biosynthesis, is the major determinant of smoky aroma in cultivated tomato. Using a combinatorial omics approach, we identified the NON-SMOKY GLYCOSYLTRANSFERASE1 (NSGT1) gene. Expression of NSGT1 is induced during fruit ripening, and the encoded enzyme converts the cleavable diglycosides of the smoky-related phenylpropanoid volatiles into noncleavable triglycosides, thereby preventing their deglycosylation and release from tomato fruit upon tissue disruption. In an nsgt1/nsgt1 background, further glycosylation of phenylpropanoid volatile diglycosides does not occur, thereby enabling their cleavage and the release of corresponding volatiles. Using reverse genetics approaches, the NSGT1-mediated glycosylation was shown to be the molecular mechanism underlying the major quantitative trait locus for smoky aroma. Sensory trials with transgenic fruits, in which the inactive nsgt1 was complemented with the functional NSGT1, showed a significant and perceivable reduction in smoky aroma. NSGT1 may be used in a precision breeding strategy toward development of tomato fruits with distinct flavor phenotypes.

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SUMMARY Tomato ( Solanum lycopersicum L.) has become a popular model for genetic studies of fruit flavor in the last two decades. In this article we present a study of tomato fruit flavor, including an analysis of the genetic, metabolic and sensorial variation of a collection of contemporary commercial glasshouse tomato cultivars, followed by a validation of the associations found by quantitative trait locus (QTL) analysis of representative biparental segregating populations. This led to the identification of the major sensorial and chemical components determining fruit flavor variation and detection of the underlying QTLs. The high representation of QTL haplotypes in the breeders’ germplasm suggests that there is great potential for applying these QTLs in current breeding programs aimed at improving tomato flavor. A QTL on chromosome 4 was found to affect the levels of the phenylalanine‐derived volatiles (PHEVs) 2‐phenylethanol, phenylacetaldehyde and 1‐nitro‐2‐phenylethane. Fruits of near‐isogenic lines contrasting for this locus and in the composition of PHEVs significantly differed in the perception of fruity and rose‐hip‐like aroma. The PHEV locus was fine mapped, which allowed for the identification of FLORAL4 as a candidate gene for PHEV regulation. Using a gene‐editing‐based (CRISPR‐CAS9) reverse‐genetics approach, FLORAL4 was demonstrated to be the key factor in this QTL affecting PHEV accumulation in tomato fruit.

Graphical abstract

Sugar beet leaves can be a viable and economically interesting source of high‐quality protein for the food industry. We investigated how storage conditions and leaf wounding at harvest affect the content and quality of the soluble protein. After collection, leaves were either stored intact or shredded to mimic wounding induced by commercial leaf harvesters. Leaf material was stored in small volumes at different temperatures to assess leaf physiology or in larger volumes to assess temperature development at different locations in the bins. Protein degradation was more pronounced at higher storage temperatures. Wounding accelerated the degradation of soluble protein at all temperatures. Both wounding and storage at higher temperatures greatly stimulated respiration activity and heat production. At temperatures below 5°C, ribulose‐1,5‐biphosphate carboxylase oxygenase (RuBisCO) in intact leaves was preserved for up to 3 weeks. At temperatures of 30–40°C, RuBisCO degradation occurred within 48 h. Degradation was more pronounced in shredded leaves. In 0.8‐m3 storage bins at ambient temperature, core temperatures rapidly increased, up to 25°C in intact leaves and up to 45°C in shredded leaves within 2–3 days. Immediate storage at 5°C greatly suppressed the temperature increase in intact but not in shredded leaves. The indirect effect of excessive wounding, that is, heat production, is discussed as the pivotal factor responsible for increased degradation of protein. For optimal retention of soluble protein levels and quality in harvested sugar beet leaves, it is advised to minimize wounding and to store the material at temperatures around −5°C. Practical Application To preserve the soluble protein content and quality for at least 3 weeks, sugar beet leaves should be harvested with minimal wounding and stored at temperatures between 1 and 5°C. When aiming to store minimally wounded leaves in larger volumes, it must be ensured that the product temperature in the core of the biomass meets the temperature criterium or the cooling strategy must be adjusted. The principles of minimal wounding and low temperature storage are transferable to other leafy crops that are harvested for food protein.