Evaluation Of Fruit Flavor Quality And Exploration Of Key Genes For Aroma Formation In Peach Germplasm Resources

Peach(Prunus persica L.Batsch)is the third largest deciduous fruit tree in China and belongs to the Rosaceae family.Peach germplasm resources are abundant and fruit types are diverse.Therefore,systematically evaluating the flavor quality of different peach cultivars,clarifying the degree of contribution of characteristic aroma compounds,and then screening peach germplasm resources with characteristic flavors,and mining the genes related to the formation of key aroma compounds by bioinformatics means,are very important references for future peach aroma directed breeding.In this study,56 peach cultivars were used for sensory evaluation of flavor quality and overall aroma information characterization by using electronic nose technology to screen for distinctive germplasm resources;eight famous peach cultivars were used as experimental materials to construct aroma fingerprints by GCMS and GC-IMS,and the contribution of characteristic aroma compounds was evaluated by OAV.On the basis of this,transcriptome sequencing was performed on the developing fruits of ‘Jinchun’ and ‘Hikawa Hakuho’,and the key genes for the formation of floral aroma compounds were extracted from them by screening differentially expressed genes and bioinformatics.The main results of the study are as follows:1.56 peach cultivars were evaluated in color,flavor,aroma and texture,using the "Reasonableness and Satisfaction Index" sensory evaluation method.In the overall score,‘Da Yu’ and ‘Hu Jing Mi Lu’ scored the highest,which means that the fruit has the best sensory sensation,attractive appearance,rich aroma,delicious and is a highquality fresh peach cultivar.The sensory quality of ‘Yan Bao’ and ‘Huang Jin Mi 1’with no obvious aroma and light flavor,which is less acceptable to consumers.2.The overall aroma information of 56 peach cultivars was analyzed by electronic nose,which could distinguish a few peach cultivars with specific aroma compounds(‘Yu Fei’,‘Zao Bai Hua’,‘Hu You 005’,‘Long Hua Shui Mi’ and ‘Jin Xiang’).The contribution of LDA was only 62.44%,which was not as effective as PCA.The results showed that in the distinction of different peach cultivars,the sensors W1W(sulfide,terpenoids),W1S(methane),W2S(ethanol)and W2W(organic sulfide)were mainly responsible for the distinction.3.A total of 70 compounds were detected in eight peach cultivars by GC-MS,among which aldehydes and lactones accounted for the largest content.Cluster analysis revealed that ‘Xin Feng Mi Lu’,‘Jin Guan’,‘Dai Tuan Mi Lu’ and ‘Jin Xiu’were the most similar in terms of aroma composition and content.By calculating the OAV of each compound,the top five contributing substances were γ-decalactone,β-ionone,hexanal,2-hexenal and linalool,and the aroma types of each peach cultivar were also identified.‘Hikawa Hakuho’,‘Jin Xiang’ and ‘Jin Chun’ belonging to“floral” aroma cultivars,the remaining cultivars belong to the “peach aroma” cultivars.4.26 compounds were detected by GC-IMS in eight peach cultivars,among which aldehydes accounted for the largest proportion;GC-IMS fingerprint showed the differences of compounds among different cultivars,with strong signals of alcohols,ketones and some unknown compounds in ‘Hikawa Hakuho’.In ‘Hu Jing Mi Lu’,there were many esters,such as methyl acetate and 2-methyl propyl acetate;in ‘Jin Chun’ and ‘Jin Xiang’,(E)-2-pentenal,3-methylbutyraldehyde.The principal component analysis showed that ‘Da Tuan Mi Lu’,‘Xin Feng Mi Lu’,‘Jin Guan’ and‘Jin Xiang’ were close to each other,indicating that their aroma compounds were similar in composition and content,which was consistent with the results of GC-MS.5.Aroma compounds were detected and transcriptome sequencing analysis was performed on five fruit stages of ‘Jin Chun’ and ‘Hikawa Hakuho’.Through RNASeq and weighted gene co expression network construction(WGCNA)analysis,key genes regulating the formation of "floral aroma" compounds were identified from PSY1,PDS1,ZDS2,CRISO1,LCYb1,CCD1,CCD4,and TPS1 genes.The acquisition of these genes laid the foundation for the establishment of a transcriptional regulatory network for the formation of characteristic aroma substances in peach fruits in the future.