Genetic Mechanism And Gene Mapping Of Glossy Fruit Skin In Cucumber

Glossy fruit skin is one of the highly valuable appearance quality traits related to market values incucumber （Cucumis sativus L.）. To date, few researches about glossy fruit skin in cucumber have beenreported and the molecular mechanism of its formation is unclear. In this study, inbred line （‘1101’） withglossy fruit skin and inbred line（‘1116’,‘9930’,‘1107’）with dull fruit skin, and their six generationgenetical populations were used as experimental materials for genetic analysis and gene mapping.Bulked segregate analysis （BSA） method and simple sequence repeat （SSR） technique were employedto map G gene in two F2populations （‘1101’ב1116’ and ‘1101’ב9930’）. SSR markers which areclosely linked to G were obtained and verified, and candidate genes for G were predicted according tothe cucumber genome sequence. In addition, in order to study the effect of different grafting stocks ongloss of cucumber fruit skin and wax powder content, cucumber scions（‘9110Gt’,‘1101’,‘1116’,‘02484’ and ‘081006’） were grafted on the stocks of cucurbita ficifolia and Huofenghuang. And thescions ‘1101’ and ‘1116’, which are markedly different in phenotype, were grafted reciprocally. Thestudy will contribute to molecular assisted selection, fine mapping and cloning of G gene, andresearches about formation mechanism of glossy fruit skin in cucumber. The results are as follows:（1） The fruit skin of all plants in F1were grossy, segregation ratio of plants with glossy and dull fruitskin in F2populations was3:1, all the plants in BC1P₁were grossy, and segregation ratios of plantswith glossy and dull fruit skin in BC1P₂、BC1P₃、BC1P₄populations was1:1. The genetic analysisshowed that a single dominant nuclear gene, G（glossy fruit skin）, dominates the glossy fruit skintrait in cucumber inbred line ‘1101’.（2）748of2136markers were screened polymorphism between P₁（‘1101’）and P₂（‘1116’）. In F2population of ‘1101’ב1116’,28SSR markers were obtained through BSA and G gene was mappedto a linkage group corresponding to chromosome5of cucumber. The flanking markers CS28andUW013295were linked to the G gene with genetic distances of1.5and4.8cM, respectively.（3） Furthermore,50of194markers on Chr.5showed polymorphism between P₁（‘1101’）and P₃（‘9930’）.In F2population of ‘1101’ב9930’,22SSR markers were obtained through BSA and G gene wasmapped to Chr.5between SSR11012and SSR06003, with genetic distances of5.5and4.8cM,respectively.（4） The physical region between SSR11012and SSR06003, which was the overlapping region of thetwice gene mapping, was about1087kb and100candidate genes were predicted, of which10candidate genes are related to pectin and fat synthesis and metabolism.（5） Marker verification showed that the accuracy rate of Cs28, UW013295, SSR11012, SSR06003in20cucumber lines was80%,85%,80%,90%, respectively.（6） The stock of cucurbita ficifolia can increase wax powder content slightly but the effect on gloss ofcucumber fruit skin was not significant. The stock of Huofenghuang can increase gloss level anddecrease wax powder content significantly. The effect of cucumber stocks on gloss of cucumberskin, wax powder content was not significant. The effect of stocks on scions was not heritable.