## 1 Introduction  
Plum belongs to the _Prunus_ genus in the Rosaceae family. It has a long cultivation history in China and is also an economically important fruit worldwide due to its bright color and rich taste. With the shift in agricultural industry structure and the decline in the benefits of traditional dominant fruits, plums have become a key driver in advancing the fruit industry and promoting rural revitalization. This is due to their strong adaptability, early fruiting, rapid yield, quick return on investment, ease of management, and economic, social, and ecological benefits [1]. According to FAO (2022) statistics, the cultivation area of plum in China is 1.978 million hectares, with a yield of 6.63 million tons [2]. Currently, there are many types of plums available in the market, and the harvesting period in Northeast China can extend from late June to mid-September. While consumers have more choices, aroma, an important indicator of fruit flavor quality, has become one of the important factors, attracting consumers and enhancing their purchasing power [3]. Therefore, fruit aroma breeding has gradually become a hot research field, and exploring the changes in the aroma components of different mature plum varieties is crucial in clarifying the aromatic compound structure of plum fruits and screening specific plum germplasm research. During the fruit ripening process, aromatic compounds impart a unique odor to plants, affecting the quality of fruit aroma. They also have important effects on pollination and plant defense [4; 5]. The aroma of fruits is relatively complex, and current research suggests that the types and contents of their intrinsic volatile components are the main reasons for presenting different aroma characteristics [6; 7]. [PERSON] et al. pointed out an investigation into the volatile compounds and aroma characteristics of litchi fruits from six distinct germplasms, categorized into special-early-maturing and early-maturing types. Their findings revealed that the alcohols, aldehyde ketones, and lipids were the main volatile components of the special-early germplasm. In contrast, the early germplasm was characterized by a different set of main volatile compounds, with terpenoids, including both monoterenes and sesquiterpene, as well as alcohols, being the most significant [8]. At present, more than 100 aroma components have been detected in plum fruit, with the primary types being alcohols, esters, aldehydes, ketones, terpen, and phenols, among which alcohols, esters, and aldehydes have the highest content [9; 10]. [PERSON] et al. revealed that compounds such as nonanal, 1-hexanol, benzaldehyde, \(\gamma\)-octadecone, and \(\gamma\)-decanoic account for a significant proportion of the aroma components in plum fruit [11]. [PERSON] et al. found that benzene, isoborneol, (E,Z)-2,6-nonandienal, and benzyl tglate could serve as markers to distinguish the primary substances in the 'Kongxin' plum [12]. Among the current plum cultivation varieties, most are medium to late maturing, while there is a relative scarcity of high-quality early-maturing varieties. The evaluation of fruit quality mainly focuses on indicators such as fruit size, sugar and acid components, and anthocyanin content [13]. Researchers are primarily focused on the presence or absence of aroma during the breeding process, with limited investigation into the types, contents, and compositions of aroma substances [14]. This study selected 38 plum varieties, mainly cultivated in Liaoning, Jilin, and Heilongjiang provinces, to compare, analyze, and identify the content of mature flesh aroma compounds in early- and mid-late-maturing plum germplasm. By determining the composition of aroma components at different maturity stages, the research aims to provide new insights for the assisted identification and breeding of plum germplasm.