1College of Horticulture，Northwest A&F University，Yangling 712100，Shaanxi，China；2Institute of Vegetables and Flowers，Chinese Academy of Agricultural Sciences，Beijing 100081，China；3School of Food and Biological Engineering，Hefei University of Technology，Hefei 230601，Anhui，China；4China Agricultural Genome Institute at Shenzhen，Chinese Academy of Agricultural Sciences，Shenzhen 518124，Guangdong，China；5College of Bioscience and Biotechnology，Hunan
Agricultural University，Changsha 410125，Hunan，China；6Hunan Vegetable Research Institute，Changsha 410125，Hunan，China
Abstract：Chlorophyll content is closely related to leaf photosynthesis efficiency and crop yield potential，and it is also an important physiological index of crops．Through conducting EMS mutagenesis on seeds of cucumber line HN3，the mutant yl-2 with yellow leaf was screened and obtained．Taking the yellow leaf mutant yl-2 and wild-type cucumber HN3 as parents，this study constructed a BC1F2 seperation population．Genetic analysis showed that this mutant was controlled by a recessive single gene．Through DNA pooling sequencing，we used MutMap strategy to find mutant gene，and obtained 4 satisfactory SNP loci．These 4 SNP loci were distributed in the 13-19 Mb physical interval on cucumber chromosome 6．Only one SNP i. e. SNP17451330 among these 4 SNP was a missense mutation，located on the gene（Csa6G385090），and the other 3 were all located on intergenic variants．By biological information analysis we found that gene Csa6G385090 encoded chlorophyll a oxygenase CAO，and amino acid mutation caused by SNP17451330 was located in the conserved domain of CAO protein．The dCAPS marker designed according to SNP17451330 was co-separated with the leaf color phenotype of the population plants，indicating that Csa6G385090 was most likely to be the candidate gene for the yellow leaf mutant yl-2．
