QTL Mapping And Candidate Gene Analysis Of Sugar And Acid Content In Grape Fruit

The contents of soluble sugar and organic acid in grape fruit affect the flavor and quality of grape.China is a large grape producing country,so it is of great significance to cultivate new grape varieties with high quality to study the inheritance and regulation mechanism of sugar and acid content in grape fruits.This study using HPLC technique in three grape fruits hybrid group to determine the content of soluble sugar and organic acid,with the grapes high-density molecular genetic map,QTL detection soluble sugar and organic acid traits to select candidate genes that may be related to sugar and acid accumulation in grape fruit,the functions of candidate genes were analyzed and verified by q RT-PCR.Main conclusions are as follows:1.The distribution characteristics of sugar and acid content in the hybrid population of'Zhuosexiang'�'Red Globe','Red Globe'�'Venus Seedless'and'Red Globe'�'Shuangyou'were analyzed.The contents of fructose,glucose,oxalic acid,tartaric acid,malic acid and citric acid in the three hybrid populations were widely distributed.The soluble sugars in grape fruits were mainly fructose and glucose,and the organic acids were mainly malic acid and tartaric acid.The content of fructose varied from 41.22 to 119.00 mg?g^-1FW,and the content of glucose varied from 45.05 to 178.11 mg?g^-1FW.The contents of tartaric acid varied from 0.73 to 8.65 mg?g^-1FW,while the contents of malic acid varied from 0.17 to 8.11 mg?g^-1FW.The combination heritability of each material is higher than 75%,which can be stable inheritance in parents and offspring.In the three hybrid combinations,there was a certain proportion of Ultra-high parent plants,and the HH rate was different.2.Based on three different grape integrated genetic maps,combining with the sugar and acid content data of grape hybrid offspring,with using Map QTL6.0 and R/qtl software to locate the sugar and acid traits of grape fruits.In the'Red Globe'�'Shuangyou'population,QTLs related to fructose were located on LG1;QTLs related to glucose were located on LG6;QTLs related to malic acid and total acid on LG11;QTLs related to glucose and total sugar were located on LG13;QTLs related to fructose,glucose and total sugar were located on LG14;QTLs related to total sugar,oxalic acid and malic acid were located on LG17.In the'Red Globe'�'Venus Seedless'population,QTLs controlling oxalic acid,malic acid and total acid were located on LG18.In the'Zhuosexiang'�'Red Globe'population,the QTLs controlling both fructose and total sugar were located on LG5.QTLs controlling both malic acid and citric acid were located on LG 6.The QTLs controlling both total acid and malic acid as well as citric acid and total acid were located on LG13.3.According to the QTL detection results of sugar and acid traits,four candidate genes that may be related to sugar and acid contents accumulating were selected,including VIT?213s0019g05250,VIT?211s0016g03400,VIT?211s0118g00200and VIT?201s0011g00240,by using the gene function annotation information of the reference grape genome and NCBI.The relative expression of candidate genes were analyzed by q RT-PCR.It was found that genes VIT?211s0016g03400,VIT?211s0118g00200 and VIT?201s0011g00240 may be involved in the accumulation of soluble sugar in fruit.The gene of VIT?213s0019g05250 mays affect the content of malic acid and participate in malic acid metabolism.