Strawberry Fruit Quality Evaluation And Aroma Resource Mining

Strawberry(Fragaria×ananassa Duch.)is a perennial herb of the genus Fragaria in the Rosaceae.The fruit is bright in color,rich in aroma,sweet and sour,has the characteristics of short planting cycle,long harvesting period and high economic benefit.It is a small berry with high economic value and nutritional value.At present,the research on the quality of strawberry is constantly deepening.However,there are many varieties of cultivated strawberries and full of flavors.At the same time,most of the facility cultivation adopts ridged ground cultivation.The quality is unstable and there are difficulties in high-quality,safe,efficient and standardized production.Therefore,it is particularly important to systematically evaluate the fruit quality of cultivated strawberries,clarify their classification criteria,and then select varieties with excellent comprehensive traits.For the variety of strawberry with distinctive flavors,it is particularly important to clarify the molecular mechanism of their main flavor compounds.In this paper,a variety of cultivated strawberries are used as test materials,and the quality is evaluated by testing the soluble sugars,organic acids,anthocyanins,fruit aroma and other indicators at the mature stage Then divide the sweet and sour taste and aroma type.On this basis,the transcriptome sequence of the cultivated strawberry "Tokun" with characteristic aroma was further carried out to obtain the gene expression lineage during fruit development period.To screen the differentially expressed genes and unearth the genes related to ’Tokun’ about ’peachy’ flavor.Lay a theoretical foundation for the study on the molecular mechanism of the synthesis of characteristic flavor substances in cultivated strawberries.The main findings are as follows:1.Using 15 domestic and foreign cultivated strawberry varieties as materials,the soluble sugar,organic acid,and anthocyanin content of the ripe fruit were tested and analyzed.The result shows:The soluble sugar and organic acid content of each component in the 15 varieties of strawberry have the same trend,but there are differences in their absolute content.The total sugar content is between 31.86mg/-58.62mg/g,all with the highest fructose content,accounting for 43%-54%of the total sugar content,and overall Fructose>Glucose>Sucrose.It is found that the ratio is less affected by varieties.The total sugar content of ’Xuexiang’(the highest)is about 1.84 times that of ’Yanli’(the lowest).The total acid content is between 3.99mg/g-7.89mg/g.Citric acid is the main organic acid,accounting for 49%-75%.Malic acid>Oxalic acid in most varieties,but’Xuexiang’ is Oxalic acid>Malic acid.In the detection of anthocyanin,white varieties(’Xuexiang’,’Snow White’)<pink varieties(’Tokun’)<red varieties,there are obvious differences in the total content.Pelargonine-3-glucoside(Pg3G)is the main anthocyanin content,accounting for 53%-89%,and the highest in ’Jingtaoxiang’ is 127.01 ug/g.Cyanidin-3-glucoside(Cy3G)works together with strawberry anthocyanins,the content is significantly less than Pg3G,and the highest ’Ssanta’ is only 34.78 μg/g.According to the sugar-sour ratio and sweetness value,the fruit is divided into groups based on the sweet and sour flavor of the fruit.White(’Xuexiang’.’Snow White’)and pink(’Tokun’)are all with better flavors,and’Hongyu’.’Jingzangxiang’,’ Yanli’,’Ningyu’and’Sachinoka’ are light in taste,sweetness dominates.2.Using 16 domestic and foreign cultivated strawberry varieties as materials,the volatile compounds in ripe fruit were detected and analyzed.The results showed that a total of 68 volatile organic compounds(VOCs)were identified for 16 riped strawberries.Among them,esters have the most types of volatile organic compounds,the total content of esters is also the highest,alcohols and aldehydes are the next,and ketones are the least.There are 8 volatile components shared by 16 strawberry varieties,namely methyl butyrate,methyl caproate,hexyl acetate,y-laurolactone,hexanal,E-2-hexenal,DMMF and hexyl Acid.In addition,high levels of ethyl caproate,methyl caprylate,linalool and nerolidol were detected in 12 varieties.Furthermore,the corresponding aroma value is calculated by the threshold value and absolute content of each VOC.Based on the description of the VOC aroma and the established private volatile component(PVC)spectrum,the characteristic aroma components of strawberry varieties are determined and four kinds are divided Fragrance type:Peachy,Pineapple,Fruity,Floral3.Using four development period(green period,green to white,white period,mature period)of ’Tokun’as materials to perform transcriptome sequencing,and construct a gene expression profile consisting of 45435 genes.It was found that the high abundance genes included 12S seed storage protein CRA1-like gene,cruciferin PGCRURSE5-like gene,lipid transfer protein EARLI 1,and metallothionein-like protein.A total of 9921 differentially expressed genes(DEG)were screened out by differential expression analysis of adjacent developmental processes,of which 290 DEGs were shared by the three comparison groups.Clustering for 290 common DEGs,it was found that 140 highly expressed genes at the green period clustered into one category,and continued to be down-regulated with fruit development.On the contrary,86 highly expressed genes at mature period clustered into one category.The performance is a continuous upward adjustment.GO enrichment analysis found that protein heterodimer activity(GO:0008061),zinc ion binding(GO:0008270),ATP dimethylallyl transferase activity(GO:0009824)and other which under the first level of molecular fuction were significantly enriched.KEGG enrichment found that the synthetic pathways of esters,flavonoids,terpenoids,and sugar acids,as well as the upstream pentose phosphate,carbon metabolism and other basic metabolic pathways are significantly active,especially the ester synthesis-related pathways and key enzymes in them are significantly enriched.On this basis,the transcription factors related to fruit quality were excavated,and 13 transcription factor families including 22 transcription factors were found.In addition to the common NAC,GRF,WRKY,bHLH,MADS-box and ERF families,there are also IAA27,PIF4,ZAT10,GT4 protein and DOF 1.2,etc.These candidate genes are an important starting point for subsequent research on the function of fruit quality-related genes.