Construction The Chromosome Segment Substitution Lines And Identification Of Genes Related To Parthenocarpy In Cucumber

Parthenocarpy as an important economic trait of fruit plants,it is closely related to yield and quality,and improving the ability of single fruiting has naturally become an important purpose of breeding.Cucumber(Cucumis sativus L.)is one of the main cultivated vegetables in China,and the phenomenon of single fruiting is common in cucumber,so cucumber has the advantage of carrying out the study of single fruiting.At present,there are different views on the study of controlling the genetic gene of cucumber parthenocarpy,and the key genes have not been found.Therefore,it is very important to excavate the effective genes related to cucumber parthenocarpy for improving cucumber cultivars with high parthenocarpy rate.In this study,two cucumber varieties(ZK:weak parthenocarpic variety;BY:strong parthenocarpic variety)with obvious differences in parthenocarpy rate were used to construct a set of segment substitution lines using SSR molecular markers assisted breeding.BY is the donor parent,and ZK is recipient parent.During the process,the cucumber CSSLs were gained after three generations of backcrossing,which were contained the donor parent’s chromosome substitution fragments for the recipient parent’s genetic background.Meanwhile,we used the SSR markers to choose the molecular markers closely linked to parthenocarpy genes.The genes related with cucumber parthenocarpy were found by the RNA-Seq in the cucumber parthenocarpic variety CSSLs and non-parthenocarpic variety ZK.Candidated genes were selected by expressions and functions.Then gene transient expression method was used for rapid functional verification about the part candidate genes of cucumber parthenocarpic fruits of CSSLs and ZK in different early stage after anthesis.The results of this study are as following:1.The average parthenocarpic percentage of intergenerational groups in construction of CSSLs was continuous distributions,and parthenocarpic trait in line with with quantitative genetic characteristics.Investigating phenotypic characters of CSSLs and their parents.During the repeated processes of backcrossing with ZK,the characters of CSSLs tend to recurrent parents in genetic background.So,It can be judged that the fragments with genes of strong parthenocarpic ability were inserted successfully and the number of inserted fragments is gradually reduced.2.In this study,a total of 36 pairs of SSR primers with polymorphism between ZK and BY were obtained from 70 pairs of SSR primers,which uniformly distributed on 7 chromosomes from the genetic linkage map.The map constructed by 90 SSR markers contains 7 linkage groups with a total length of 652cM by He[119].Using 36 primer pairs to verify CSSLs,the polymorphism of CSSLs is 96.8%.3.RNA-Seq technique was used to collect the transcriptome datas of cucumber fruits 1 day after anthesis for screening of parthenocarpy genes with CSSLs and ZK as materials in this study.Trough comparative analyses,2078 DEGs associated with parthenocarpic fruit were obtained,including 1021 genes up-regulated and 1057 genes down-regulated.It is speculated that selected 12 genes involved in fruit development process were analyses in early developmental parthenocarpic fruit.Genes related to ethylene and ABA play negative role in forming parthenocarpic fruit,the expression of CTK genes and auxin receptor genes in parthenocarpic fruit was higher than that in non-parthenocarpic fruit.The effects of genes related to response regulators between different parthenocarpic fruit remains to be studied.4.The expression of these genes were further analyzed by qRT-PCR,and the expression of genes related to ABA signal transduction and ethylene signal transduction in CSSL was lower than that genes of auxin signal transduction was lower ZK,indicating that the auxin signal transduction pathway was enhanced in the CSSL,while the ethylene and abscisic acid pathways were inhibited,thus promoting the parthenocarpy.