Analysis Of Chromosome Evolution And Creation,Identification Of Alien Addition Lines In Main Cucumis Species

Cucumber(Cucumis sativus L.,2n = 2x = 14)belonging to Cucurbitaceae Cucumis,is an important vegetable crop in the world.The genetic basis of cucumber is very narrow,and important resistance genes are abscent.Cucumis sativus is generally sensitive to low temperature stress and other biotic or abiotic stress.The genus Cucumis is abundant in wild relative species,including about 52 species.Elucidating the evolution relation and their genomic organization in Cucumis plays an important role for the exploring excellent genes.Cucumis hystrix origining from Yun nan Province,China,is a kind of relative wild species with resistance to nematodes,gummy stem blight,downy mildew resistance,tolerance to low temperature and weak light.It is especially important to improve cucumber cultivars by interspecific hybridization.In this study,we studied the chromosome evolution in Cucumis species by FISH(fluorescence in situ hybridization)with 45S,5S rDNA as well as single copy gene(Scg)as probes.We concluded that the base chromosome number from 12 to 7 involve chromosome broken and reintegration.At the same time,to accelerate the process of cucumber improvment,we hybrized the allotetraploid with C.sativus to creat the alien addition lines.The main results are as follows:1.Cucumis chromosome evolution research revealed by 45S and 5S rDNA chromosome localizationIn present study,FISH was conducted to study the location of 45S rDNA and 5S rDNA among 20 Cucumis accessions,including cultivars and wild accessions.Our results showed that the number of 45 S rDNA sites varied from one to five pairs in different accessions,and most of them located at terminal regions of chromosomes.Interestingly,up to five pairs of 45 S rDNA sites were observed in C.sativus var.sativus which has the least chromosome number,i.e.2n=14.Only one pair of 5S rDNA sites was detected in all accessions except for C.heptadactylus,C.sp and C.spp that had two pairs of 5S rDNA sites.The distributions of 5S rDNA sites showed more variation than those of 45 S rDNA sites.2.Cucumis chromosome evolution research revealed by single copy gene FISHIn this study,we conducted the Cp experiments with Scg pool of cucumber chromosome 6 and 9 Scg from cucumber chromosome 5 to analysis the chromosome evolution relationship between cucumber and melon.Obvious signals were observed oncucumber pachytene chromosome by chromosome painting with segmented probes.The probes covered regions from 21-26Mb of cucumber chromosome 6 produced two signals on C.melon pachytene chromosome.Nine single copy gene probe from cucumber chromosome 5 were used to study the evolution relationship between cucumber and C.melon.The match information showed that 5 probes were located at the chromosome 9 of C.melon,and 4 were located at chromosome 10.3.Creation of alien chromosome lines based on the interspecific hybridization between Cucumis hystrix and Cucumis sativusWe conducted reciprocal cross between allotetraploid and Cucumis sativus.As a result,we obtained allotriploid materials,introgression lines and alien addition lines(AAL)materials.We identified these materials by FISH with specific repetitive sequence and simple sequence repeats(SSR).Our results showed that the materials we have obtained are reliable introgression lines and AAL.