Fine Mapping Of A Dwarf Gene(cp) In Cucumber,Cucumins Sativus L.

The compact plant architecture is an important agronomic traits in cucumber(Cucumis sativus L.)breeding,it has the potential to be used in high-density,efficient cultivation and once-over mechanicalharvesting of cucumber production.Compact growth habit is controlled by a simply inherited recessivecompact gene(cp).Initial fine genetic mapping has delimited the cp locus to a 220 kb genomic DNA region which is cosegregated with cytokinin oxidase gene(CKX).To narrow down the region of cp gene,we researched fine mapping of the cp gene based on original research,the results are as follows:1.A new set of large F2 individuals was constructed,which were derived from the same two inbred cucumber lines,WI7201(compact vining)and WI7200(regular vining).Recombinant plants were screened bythe flanking markers UW084680 and UW084870,which came from cp gene fine mapping in 2011,and among the 2043 F2 plants,there were 65 recombinants between them.Based on the cucumber genetic and physicalmap information in this region,eighty-eight SSRs(simple sequence repeat,SSR)and seven STS(sequence-taggedsites,STS)primers between UW084686 and UW084680 were designed and screened for polymorphism between the two parents.Four SSRs and one STS marker were used to further analysis.Among the 2043 F2 plants examined,no recombination was found between the compact locus and the two markers UW057998 and cp-STS-6.The cp locus was delimited to a 178 kb genomic DNA region.Mapping effort thus far resulted in three flanking markers,UW063076?CKX-indel and UW058058,which was 0.06 and 0.13 cM away from the cp locus,respectively.This result excludes the possibility of CKX as a candidate gene.2.Because of serious segregation in the last population,we constructed a new set of large F2 individuals,which were derived from the two inbredcucumber lines,WI7201(compact vining)and CCMC(regular vining),to narrow down the region of cp gene.Recombinant plants were screened by the flanking markers UW084680 and UW084870and among the 2243 F2 plants,there were 60 recombinants between them.Based on the cucumber genetic and physical map information in the region which we mapped,Fifteen STS(sequence-tagged sites,STS)primers were designed and screened for polymorphism between the two parents.Based on the sequencing results,we designed two STS makers,three indel markers and three dCAPS markers for further analysis.Among the 2243 compact F2 plants,no recombination was found between the compact locus and the marker NWSTSI2-dCAPS.Finally the cp locus was located to a 13kb genomic DNA region.Mapping resulted in three franking makers,NWSTS-9,NWSTS14-indel and NWSTS15-dCAPS which was 0.05 and 0.1 cM away from the cp locus,respectively.3.Gene prediction in this region only found one gene which called ER(transmembrane receptor protein kinase)was a possible candidate gene of the compact locus.This result will lay the foundation not only for screening andconfirmation cp gene but also for molecular marker-assisted breeding in the cucumber.