## 3 Results and Analysis  
### Analysis of Differences in 38 Plum Resources of Fruits' Aromatic Components  
Previous findings indicated that aldehydes and esters constituted the most abundant classes of compounds present in plum fruits [16]. This study yielded comparable findings. Based on the variation in the primary functional groups of the compounds, successful quantification was completed of 138 identified aroma components, comprising 26 aldehydes, 63 esters, 13 ketones, 30 alcohols, and six other compounds in 38 plum germplasm resources, as shown in Figure 1a. Figure 1: Aromatic components of the types and contents in 38 plum germplasm resources. (**a**) shows the number of aroma compounds among different plum germplasm resources, (**b**) shows the contents of total volatile compounds in 38 plum germplasm resources. Notably, the number of aroma compounds varied significantly among different plum germplasm resources, ranging from 14 to 53. Dadanguo exhibited the highest number of aroma components, with 53 types. This was followed by Qiulizi and Jinxxiiangjiaoli, with 46 and 45 types, respectively. XY had the lowest count, with only 14 aroma components. Among the 38 tested plum resources, Huangganhe plum had the highest number of aldehyde substances in its fruit, containing 14 species; Dadanguo plum had the highest number of esters, with 30 types; Jisheng plum had the highest content of ketones, containing 14 species; and Qiulizi and Friar plums had the highest alcohol content, both at 11 species. In XY, aldehyde aroma components constituted the largest proportion of total aroma components, at 57.14%. In Heibali, ester aroma components made up the highest proportion, accounting for 63.41%. Jisheng had the highest proportion of ketone aroma components at 15.63%. The highest proportion of alcohol aroma components was found in fruits from 10 to 27, at 47.37%. Among 38 plum varieties, the number of aldehydes ranged from 3 to 13, esters from 3 to 30, and alcohols from 3 to 11. Ketones were relatively scarce, ranging from 0 to 5. The results indicate that esters, aldehydes, and alcohols were the leading contributors to the aroma profile, collectively comprising over 78.00% of the total content. Only a small fraction of the resources was primarily composed of ketones. Among the varieties, Jinxxiangiaoli had the highest ester content, measuring 323,467.43 \(\upmu\) kg\({}^{-1}\), which accounted for 98.89% of its total aroma components. This was followed by Dadanguo and Heibali, with ester contents of 156,175.28 \(\upmu\) kg\({}^{-1}\) and 126,476.45 \(\upmu\) kg\({}^{-1}\), respectively. XY had the lowest ester content, at 145.75 \(\upmu\) kg\({}^{-1}\). The aldehyde content in the 38 varieties ranged from 2226.34 to 178,856.08 \(\upmu\) kg\({}^{-1}\), with Richard Early having the highest aldehyde content, representing 91.36% of its total aroma components. XY 7-1 had the highest alcohol content, accounting for 74.19% of its total. The aroma components of Taiyang fruit were predominantly ketones, making up 46.17% of its total aroma components (Figure 1b). Among the aroma components in 38 plum varieties, 13 main compounds were dominant, with the highest contents being as follows: acetic acid heyl ester, (Z)-3-hexen-1-ol acetate, hexanal, 1-hexanol, 3-hexenal, butanoic acid butyl ester, (E)-2-hexen-1-ol, hexanoic acid butyl ester, propanoic acid butyl ester, (E)-2-hexen, 1-alpha-terpineol, (Z)-2-hexen-1-ol acetate, and 1-butanol (Table 2). However, for different varieties of aroma substances, it is not only the type that shows variability but also the content. Acetic acid heyl ester had the highest content in the aroma components of Dadanguo, Jinxxixiangjiaoli, and Heibali. In Dadanguo, the second most abundant compound was (Z)-3-hexen-1-ol acetate, followed by butanoic acid butyl ester. In Jinxxixiangjiaoli and Heibali, the third most abundant compound was hexanoic acid butyl ester, but the second most abundant was different: (Z)-3-hexen-1-ol acetate in Jinxxiangjiaoli and 1-hexanol in Heibali.