Development Of Interspecific Chromosome Introgression Lines Of Cucumber And Its Genetic Evaluation

Cucumber(Cucumis sativus L.) is an important vegetable crop of Cucurbitaceae in Cucumis. Because of its narrow genetic basis, low polymorphism among cultivars, very limited intraspecific excellent resources, a few of QTLs have been mapped. It has become an important constraint factor in the process of cucumber molecular breeding. As its wild and relative species are rich in genetic resources, mining useful traits of wild species is an effective way in getting a breakthrough of cucumber breeding. In this study, progenies derived from distant hybridization between the receptor parent cultivated cucumber ’Beijingjietou’ and donor parent wild sour cucumber(Cucumis hystrix Chakr.), and multi-generational backcrossing and selfing followed, are used as test materials. It proves that exogenous genetic material in the sour cucumber has entered the progenies by molecular identification and DNA sequence analysis. On this basis, combined with marker-assisted selection and phenotypic variation analysis, chromosome segment introgression lines (CSILs) in Cucumis are constructed and given a genetic evaluation firstly. With a view to laying an theoretical foundation for improving cultivated cucumber and germplasm enhancement by a transfer utilization of wild excellent resources.1Molecular verification of DNA flow from wild sour cucumber to cultivated cucumber caused by interspecific hybridizationThe progeny population derived from interspecific hybridization between the cultivated cucumber and wild sour cucumber, and multiple generational backcrossing and selfing followed, is used in the study. The results show that DNA flow from sour cucumber to cucumber interspecific hybrid progenies on molecular level. And the genetic polymorphism is13.2%, including missing bands and new bands. The sour cucumber specific bands in progenies are abtained by RAPD primer D-11and SSR primer06632, with the size of350bp and180bp respectively. Sequence analysis shows that the identity are92.93%and96.48%respectively, though there are41and9different bases respectively, including the base transition, transversion and deletion. These results confirm that some mutations of different types occurred with DNA segments of wild sour cucumber being introduced into cucumber interspecific hybrid progenies.2Development of interspecific chromosome segment introgression lines of cucumerThe cultivated cucumber ’Beijingjietou’ with comprehensive good traits and precious rare wild sour cucumber carrying a variety of resistance traits are used as receptor parent and donor parent respectively in the study. Chromosome segment introgression lines (CSILs) in Cucumis are constructed on the basis of interspecific allotetraploid by multiple generational backcrossing and selfing, combined with SSR marker-assisted selection (MAS), with the genetic background of’Beijingjietou’. By evaluating of the number, distribution, segment size and coverage rate, it shows that the coverage rate of the group composed of17introgression lines ranges from0.8%to19.1%, with an average of6.6%.The38donor segments of CSILs exist in cucumber seven chromosomes unevenly. Their length varies from1.1cM to14.9cM, the average length is5.3cM, the total length is201.9cM and the coverage rate in the cucumber genome is23.5%.3Genetic variation analysis of agronomic traits of interspecific chromosome introgression lines of cucumer12of chromosome segment introgression lines in Cucumis and their receptor parent cultivated cucumber ’Beijingjietou’ are used as experimental materials in this study. The main characteristic agronomic traits of wild species in introgression lines are investigated and analyzed, some related QTL are detected followed. The results show that the majority of traits are extremely significant difference between recipient parent and12different introgression lines, showing the genetic characteristics of wild species. At the same time, by t test to P≤0.001as the threshold value, a total of87QTL are detected in10traits, an average of9.67QTL per character and7.25QTL each introgression line.