Abstract
The loss of volatiles results in the deterioration of flavor in tomatoes. Volatiles are mainly derived from fatty acid, carotenoid, phenylpropane, and branched chain amino acids. In this study, the tomato accession CI1005 with a strong odor and accession TI4001 with a weak odor were analyzed. The volatile contents were measured in tomato fruits using gas chromatography-mass spectrometry. The scores of tomato taste and odor characteristics were evaluated according to hedonistic taste and olfaction. It was found that the content of fatty acid-derived volatiles accounted for more than half of the total volatiles that had grassy and fatty aromas. Phenylpropane-derived volatiles had irritation and floral aromas. Branched-chain amino acid-derived volatiles had a caramel aroma. Carotenoid-derived volatiles had floral, fruity, fatty, and sweet-like aromas, preferred by consumers. A lack of carotenoid-derived volatiles affected the flavor quality of tomato fruits. The accumulation of carotenoid-derived volatiles is regulated by carotenoid cleavage oxygenases (CCDs). A tissue-specific expression analysis of the SlCCD genes revealed that the expression levels of SlCCD1A and SlCCD1B were higher in tomato fruits than in other tissues. The expression levels of SlCCD1A and SlCCD1B were consistent with the trend of the carotenoid-derived volatile contents. The expression of SlCCD1A was higher than that for SlCCD1B. A bioinformatics analysis revealed that SlCCD1A was more closely linked to carotenoid metabolism than SlCCD1B. The overexpression of SlCCD1A indicated that it could cleave lycopene, α-carotene, and β-carotene to produce 6-methyl-5-hepten-2-one, geranylacetone, α-ionone, and β-ionone, increasing the floral, fruity, fatty, and sweet-like aromas of tomato fruits. The flavor quality of tomato fruits could be improved by overexpressing SlCCD1A.
Highlights
It has been found that fruit weight and hardness have been preferentially selected in tomato breeding during long-term domestication and improvement, inadvertently resulting in the loss of alleles related to sugar and volatile synthesis [6,7]
We found that SlCCD1A and SlCCD1B were more significantly highly expressed in tomato fruits than in other tissues
The volatiles derived from fatty acid contributed to grassy, fatty, mushroom-like, floral, fruity, and fatty aromas
Summary
The flavor and quality of tomatoes has not improved with the increase in yield but, instead, decreased in modern cultivated tomatoes [2,3,4]. This is due to the significantly reduced contents of glucose, fructose, citric acid, and at least 13 volatiles in modern cultivated tomatoes [5]. It has been found that fruit weight and hardness have been preferentially selected in tomato breeding during long-term domestication and improvement, inadvertently resulting in the loss of alleles related to sugar and volatile synthesis [6,7]. Soluble sugars and organic acids provide the basic flavor for fruits and vegetables, while the characteristic aromas of volatiles are the main indicator that distinguish flavors among different fruits and vegetables [8,9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
