Effect of exogenous auxin on aroma volatiles of cherry tomato (Solanum lycopersicum L.) fruit during postharvest ripening

The phytohormone auxin has been proved to be involved in the regulation of quality traits in climacteric fruit ripening, but there was little information about the correlation between auxin and aroma volatiles in fruit. In the present study, the effect of auxin on aroma volatiles in tomato fruit during postharvest ripening was studied by treating detached tomato fruit at mature green stage with 2, 4-dichlorophenoxyacetic acid. The results showed that exogenous auxin delayed the ripening process of tomato fruit via inhibiting the ethylene production and the carotenoids accumulation, as well as the degradation of chlorophyll. In addition, exogenous auxin enhanced the accumulation of phenolic volatiles such as phenylacetaldehyde (1.57-fold), 2-phenylethanol (1.56-fold) and methyl benzoate (1.75-fold), and inhibited the production of 1-hexanol (56.59 %), 1-nitro-2-phenylethane (23.74 %), benzyl cyanide (45.69 %) and 2-isobutylthiazole (35.18 %). Exogenous auxin altered the expression of a number of key genes involved in the biosynthetic pathway of aroma volatiles, including induction of SlSAMT1, LePAR1and LePAR2, and inhibition of TomloxC, HPL, ADH2, LeCCD1s, LePAR1, LePAR2, LeAADCs, SlBCAT1. The log(2) fold change of these genes ranged between -4.53 and 3.02 compared to that in the control group. Moreover, correlation analysis revealed that changes of apocarotenoids and amino acid-derived volatiles were positively correlated with the expressions of related genes in response to auxin. The present study provided valuable information for further elucidating the regulation of tomato fruit aroma as well as quality traits during ripening.