# Molecular Regulatory Mechanisms Affecting Fruit Aroma
## 6 Main Factors Affecting Fruit Aroma Synthesis  
Fruit aroma is influenced by a variety of factors, including intrinsic genetic factors [61], plant hormones [62], the cultivation environment [63], cultivation practices [64], and postharvest storage [65]. There are differences in the aroma substances in fruits of the same citrus variety from different regions. [PERSON] et al. [66] reported that the total amount of aroma substances in the fruit juice of Kaman oranges from Vietnam was three times greater than that in the juice of oranges from Malaysia and the Philippines. The types and contents of strawberry aroma substances under soil cultivation were significantly greater than those under substrate cultivation [67]. The application of selenium fertilizer has a significant positive effect on tomato aroma [68]. The 'Salustiana' and 'Navelina' orange juices from organic and conventional cultivation systems are rich in different types of aroma substances [64]. Therefore, studying the influence of cultivation conditions on the metabolism of citrus fruit aroma substances can improve the aroma quality of citrus fruits.  
Hydrogen nanobubble water (HNW) treatment before harvest can alleviate the negative effects of fertilizer on strawberry fruit aroma. The content of flavor compounds, such as esters (e.g., ethyl acetate), acids (e.g., acetic acid), and soluble sugars (glucose, fructose, sucrose, etc.), can also be increased with treatment [69]. [PERSON] et al. [70] reported that, during storage, the contents of 31 aroma substances in 'Mor' broad-peel citrus fruits decreased more than 50%, while the contents of 13 aroma substances increased more than twofold. The loss of the former aroma substances was due to the degradation of monoterenes and sesquiterpennes. The latter increase may be due to the metabolites of alcohol fermentation, fatty acid derivation, and amino acid breakdown. In addition, the contents of aroma substances in the fruits of 'Navelina' sweet orange, 'Clemenules' ponkan, 'Prenules' ponkan, and 'Basol' ponkan are not affected by ethylene treatment. However, after ethylene treatment of 'Oronules' and 'Clemenrubi' fruit, the content of esters, such as ethyl propionate and ethyl caprylate, in the fruits of Ponkan increased [65]. Storage temperature and ethylene content are both factors that affect the aroma of fruits after harvest. Low temperature and controlled ethylene concentration can delay the ripening of fruits and subsequently affect the aroma of horticultural crops. Compared with treatment at the beginning of picking, the application of the ethylene and 1-methylcyclopropene (1-MCP) not only preserved the freshness of stored blueberry fruits but also did not have a significant impact on aroma substances [71]. The degradation effect of ethylene was effectively neutralized by 1-MCP. Compared with the CK, 1-MCP with or without ethylene increased tightness, functional component content, antioxidant activity, and inhibited the ethylene production and respiration rate. Therefore, the simultaneous use of ethylene and 1-MCP treatment guaranteed better quality and volatile compounds in blueberry fruit during the whole storage [71]. [PERSON] et al. [62] studied the effect of methyl jasmonate on the aroma quality of refrigerated 'Nanguo' pear. The results showed that the application of methyl jasmonate can affect LOX pathway-related genes and TFs, helping to prevent refrigeration-induced ester synthesis and improve pear quality. Further studies have shown that methyl jasmonate treatment activated the biosynthetic pathways of LOX, methylerythnitol phosphate (MEP), and shikimate in pear skin and pulp.