Objective  The aim of this study is to investigate the types, relative contents and differences in the aroma components of the juice of Guanximiyou and its new bud variants, as well as the possible molecular mechanisms causing the changes in the aroma components.

  Methods  Fruits juice of Guanximiyou and its bud-variant varieties Hongroumiyou and Sanhongmiyou were used as test materials to determine the aroma components by gas chromatography-mass spectrometry (GC-MS). The genes that were significantly differentially expressed were screened by transcriptome analysis, and the expression patterns of these genes were analyzed using the trend of FPKM values.

  Results  A total of 150 aroma components were detected in the three juice samples, and the aroma compounds that accounted for a large number were aromatic hydrocarbons, sesquiterpenes, aldehydes, alcohols and ketones. Guanximiyou, Hongroumiyou and Sanhongmiyou detected 59, 129 and 67 aroma compounds respectively, with their total relative contents of 4.56, 8.02 and 9.90 respectively, indicating that bud changes significantly caused changes in the aroma components and total relative content. The relative content of aldehydes was the highest, with hexanal being the main aroma component common to all three species; alcohols and ketones were the next most abundant, while furans, aromatic hydrocarbons, sesquiterpenes, esters and monoterpenes were less abundant; 32 other aroma components were also detected at very low or trace levels, all of which were unknown and unreported compounds. Transcriptome analysis was used to screen for one new gene (Citrus_maxima_newGene_12651), seven genes with significant differences in expression of Lipoxidase (LOX2.1) (cg2g001970, cg2g001980, cg2g002000, cg2g002010, cg2g002030, cg2g002040, cg2g002080 cg2g002030, cg2g002040, cg2g002080), one LOX3.1 gene (cg1g010660) and two Alcohol dehydrogenase (ADH1) genes (cg3g017900, cg3g017890), using trend analysis of FPKM values. It was tentatively hypothesized that the differences in the aroma components of the juices of the three varieties were related to the differential expression of genes in the fatty acid pathway and the isoprene pathway.

  Conclusion  Aldehydes, alcohols and ketones were the main aroma components of Guanximiyou and its bud varieties, and hexanal was the main aroma compound common to the three varieties; The significant differences in the aroma components of the fruit juices of the three varieties tested were initially hypothesized to be related to the differential expression of genes in the fatty acid pathway and isoprene pathway.