Abstract：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 mechanical harvesting of cucumber production. Compact growth habit is controlled by a simply inherited recessive compact gene (cp). Initial fine genetic mapping with 1 273 F2 plants 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, a new set of large F2 individuals was constructed, which was derived from the same two inbred cucumber lines, WI7201(compact vining) and WI7200(regular vining). Recombinant plants were screened by the flanking markers UW084680 and UW084870, which came from cp gene fine mapping in 2011, and among the 1 348 F2 plants, there were 57 recombinants between them. Based on the cucumber genetic and physical map information in this region, sixty-eight SSRs(simple sequence repeat) and one STS (sequence-tagged sites, STS) marker between UW084686 and UW084680 were designed and screened for polymorphism between the two parents. Two SSRs and one STS marker were used to further analysis. 2 621 F2 plants were used for fine genetic mapping of cp which included 1 348 F2 plants from the new set of F2 population and 1 273 F2 plants from cp gene fine mapping in 2011. Among the 2 621 F2 plants examined, no recombination was found between the compact locus and the two markers UW057998 and cp-STS-6. Finally the cp locus was delimited to a 178 kb genomic DNA region. Mapping effort thus far resulted in two flanking markers, CKX-indel and UW058058, which was 0.04 and 0.23 cM away from the cp locus, respectively. This result excludes the possibility of CKX as a candidate gene. As a result, the candidate gene of cp is located in the 178 kb region between CKX-indel and UW058058. The results will lay the foundation not only for screening and confirmation cp gene but also for molecular marker-assisted breeding in the cucumber.
