Preliminary Probe Into EMS Mutagenesis Of Cucumber (Cucumis Sativus L.)

Cucumber （Cucumis sativus L.） belongs to Cucurbitaceae and is one of the mainvegetable crops widely grown all over the world. The major aim of the cucumber breeders isto develop cucumber varieties with high yield and high quality. It is the base to creat thebreeding materials with rich genetic background for cucumber breeding. The majority of thecucumber genome has now been released, which opened a new era for exploring functionalgenes controlling those important agricultural traits of cucumber. A powerful approach fordetermining the biological functions of genes in cucumber is to produce cucumber mutantswith altered phenotypes and physiological responses.Ethyl methane sulfonate （EMS） is a stable and effective chemical mutagen. In this study,seeds of a cucumber cultivar,‘Shannong No.5’, were treated by1%EMS for12,22,24and48h （hours） to optimize EMS mutagenesis. Considering lethal dose and otherexperimentation factors,22h,1%EMS was selected out as the appropriate treatmentcondition in this experiment for ‘Shannong No.5’. Then,1200seeds of ‘Shannong No.5’ weretreated by1%EMS for22h, and541M₁plants were transplanted into solar greenhouse.Among the M₁s, plants with chlorophyll defects and other abnormalities were found. Whereasthe fertility of M₁s was very low, only79lines produced seeds after selfing.60independentM₂families comprising600M₂plants were inspected for phenotypic alteration, and11individual mutants were isolated. The mutation frequency was18.3%. Genetic analysis wascarried out in some mutant. The phenotype altered of the mutants involves fruit, flower,tendril, internode and so on. Representative mutants were described in detail in M₂plants asthe following.One mutant developed opposite tendrils, and its partial tendrils branched. Three mutantswere found in nine plants of the M₂family. That corresponds with the3:1ratio of Mendel’slaw of segregation. Further analysis in M₃generation is needed for the conformation of thismutant. The short fruit mutant has shorter and thicker fruit than wild-type and its female andmale flowers are also different from those of the wild-type. This mutant showed1/4ratio inM₂plants, and this corresponds with the Mendel’s law of segregation. So, this mutant shouldbe controlled by a single recessive gene.The long fruit mutant could produce longer and thiner fruit than wild-type, and thisphenotype could be stably inherited in M₃plants for data analysis indicates that fruit lengthand diameter have significant difference between wild-type and the mutant in M₃generation.The clustered leaves mutant is much smaller than the wild-type plant, and has decussateleaves, almost no internodes. It showed a failure to establish a nomal cucumber plant. Geneticanalysis in M₂plants showed this mutant should be caused by a single recessive gene.These mutants will be useful to cucumber functional genomic research and to cucumberbreeding.