| Orah is produced from the cross of “Temple” tangor and “Dancy” tangerine.It shows the characteristics of high sugar,low acid,late maturity,high yield and high quality,but its large number of seeds affects the taste of consumers and market acceptance to a certain extent.In order to decrease the high seed number of Orah,the seed number of “Yu Or Seedless”,which was obtained by radiation,was greatly reduced.In addition,seedless Orah was obtained by radiation mutagenesis in Israel,which not only reduced the number of seeds,but also resulted in low fruit setting rate and irregular fruit size.The purpose of this study was to compare the fruit quality of Orah and its seedless mutants,it is very important to analyze the main genetic factors which cause the phenotypic difference of “Yu Or Seedless” with fewer seeds and lower fruit setting rate at flowering stage.The main research results are as follows:1.Comparison of fruit qualityThe fruit quality of Orah,091 seedless Orah and“Yu Or Seedless”were tested.(1)the number of seeds of “Yu Or Seedless”was significantly less than that of Orah,but no significant difference was found compared with 091 seedless Orah,the seeds number of each varieties were slightly increased in 2020 comparing with 2019.(2)Among three Orah varieties,“Yu Or Seedless” and 091 seedless Orah ripen earlier,had thicken pericarp and difficulty to peel comparing with Orah.Fruit quality analysis showed that“Yu Or Seedless” had the highest total soluble solids(TSS)and ascorbic acid(Vc)and lowest titratable acid(TA)and invert sugar.2.Comparison of whole genome resequencingThe mature leaves of Orah and “Yu Or Seedless” were used as materials for genome sequencing.(1)The whole genome resequencing showed that the proportion of tandem repeats in genome of “Yu Or Seedless” account for 3.44%,only about half of Orah(7.46%),the genes located in or around of these tandem repeat sequences were conducted functional enrichment analysis.(2)GO functional enrichment showed that the divergent genes about small molecule binding and RNA binding were only involved in Orah,while “Yu Or Seedless” only involved RNA polymerase activity and ATPase activity associated with transmembrane transport of substances.(3)KEGG pathway enrichment showed the divergent genes about endocytosis and homologous recombination were only involved in Orah,while “Yu Or Seedless” only involved galactose metabolism and peroxisome.3.Comparison of leaf transcriptomeThe young leaves of Orah and “Yu Or Seedless” were used as materials for sequencing analysis using RNA-Seq technique.(1)A total of 3493 differentially expressed genes(DEGs)were identified.The GO functional annotation mainly involved DNA metabolism,chromosome structure and microtubule-based processes.(3)The KEGG pathway annotation mainly involved DNA replication,wax synthesis and mismatch repair,the genes related to sucrose synthesis were up-regulated in “Yu Or Seedless”.4.Transcriptome comparison of ovary at flowering stageRNA-Seq technology was used to analyze the flowering ovaries of Orah and “Yu Or Seedless”.(1)The RNA-seq transcriptome showed that a total of 4140 differentially expressed genes(DEGs)were existed in ovary of “Yu Or Seedless” and Orah.GO enrichment analysis showed DEGs mainly involved in carbohydrate metabolism,oxidation-reduction process,β-galactosidase complex.(2)The enrichment of KEGG pathway showed DEGs mainly involved in phenylpropanoid biosynthesis,endoplasmic reticulum protein processing and secondary metabolite synthesis.Among them,most DEGs associated with β-glucosidase,peroxidase,heat shock protein,flavonol synthase and auxin response in the early growth stage were down-regulated in “Yu Or Seedless”,while the expression of pollen-related G-receptor kinase genes were up-regulated. |
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