不同文心兰品种香气组分差异及特征酯类合成候选基因分析OA

[Objective]To clarify the differences in floral volatile components among six Oncidium cultivars and explore key candidate genes regulating the synthesis of characteristic aroma substances,and to reveal the metabolic and molecular basis of aroma differentiation in closely related cultivars.[Method]Six Oncidium cultivars,including Oncidium Twinkle'Chian-Tzy Golden',Oncidium Twinkle'Fragrance Fantasy',×Oncidopsis Bartley Schwarz(Beall)'Highland'(AM/AOS),Oncidium Hwuluduen Nova'Red Cherry',Oncidium Jairak Fragrance#564 and Oncidium Sharry Baby'Tricolor'were used as experimental materials.Solid phase microextraction coupled with gas chromatography-mass spectrometry(SPME-GC-MS)was applied to identify floral volatile components.Principal component analysis(PCA)and hierarchical cluster analysis(HCA)were used to compare aromatic characteristics among cultivars.Transcriptome sequencing and metabolome-gene association analysis were further performed on the closely related cultivars Oncidium Twinkle'Chian-Tzy Golden'and Oncidium Twinkle'Fragrance Fantasy'.[Result]A total of 113 floral volatile compounds were identified from six Oncidium cultivars,mainly consisting of terpenes,esters and alcohols.The relative content of terpenes ranged from 50.76%to 84.13%,and significant differences in composition and content were observed among cultivars.PCA and HCA results showed that Oncidium Twinkle'Chian-Tzy Golden'and Oncidium Twinkle'Fragrance Fantasy'shared the most similar aroma composition,which was consistent with their genetic relationship.Ten significantly differential volatile compounds were detected between the two cultivars.Oncidium Twinkle'Chian-Tzy Golden'accumulated abundant esters,especially isoamyl(E)-2-methylcrotonate,while Oncidium Twinkle'Fragrance Fantasy'was enriched in monoterpenes,showing obvious metabolic divergence.A total of 9 104 differentially expressed genes were obtained by transcriptome sequencing.Metabolome-gene association analysis identified TRINITY_DN114613_c1_g2(BCKDH-E1β subunit)as a key candidate gene for characteristic ester synthesis,which provides tiglyl-CoA precursors through the isoleucine degradation pathway and positively regulates the accumulation of isoamyl(E)-2-methylcrotonate.[Conclusion]This study clarified the aroma profiles and cultivar specificity of six Oncidium cultivars,and revealed the metabolic pattern and molecular clues of aroma differentiation in closely related sibling cultivars.The findings provide a theoretical reference for germplasm selection and targeted improvement of floral scent quality in Oncidium.