Construction And Phenotypic Analysis EMS Mutant Library In Cucumber(Cucumber Sativus L.)

Cucumber（Cucumis sativus L.）is an important worldwide vegetable.The genetic base of cultivated cucumber was narrow,the germplasm resources of local varieties tended to be single,and the variation rate was only 3%and 8%.Mutants are important materials for the breeding of new varieties and functional genomics research.The construction of cucumber mutant libraries can enrich the germplasm resources and advance the process of breeding.In this study,the high-quality inbred line‘32X’of the South China-type cucumber high-quality local cultivar‘Tangshan Autumn Cucumber’,was used as the material,and the mutagenesis technology was optimized by using methyl methane sulfonate（EMS）mutagenesis technology to construct a mutant library.It provided important materials for breeding new cucumber varieties and genetic analysis of important agronomic traits.The main results are as follows:1.In order to construct a cucumber mutant library,the seeds of inbred line’32X’were treated with six different concentration gradients（0%,0.4%,0.8%,1.2%,1.6%and 2.0%）of Ethyl Methane Sulfonate（EMS）for 12 hours.According to the rate of seed germination and emergence after treatments,the optimum concentration was1.6%.2.A total of 5000 seeds of‘32X’were treated with this optimal concentration,The results showed that 1920 plants survived in the M₁ generation,with a survival rate of 38.40%.Among them 1132 plants obtained self-pollinated seeds,extremely dwarf plants were obtained,and the flowering period was early.Mutants such as fruit chimeras,fruit shortening,leaf color chimeras,and fruit malformations.3.The M₂ population composed of 3743 individuals（662 lines）was constructed.Preliminarily,1055 candidate mutants were screened out,with a rate of 28.19%,among which three cotyledons and cotyledons were yellowed.There are 64 typical phenotypic variations in true leaf albino,true leaf folds,tendrils,bisexual flowers,flower buds,and fruit without bristles.The mutation rate of leaves was up to 8.68%,followed by other phenotypic organs,such as flowers（8.60%）,plant types（6.79%）,fruits（2.81%）and cotyledons（1.31%）.4.After screening,a M₃ population containing 36 typical mutant families was constructed.and 20 lines were homozygous by phenotypic identification.The main agronomic traits were focused on globular fruit,dense fruit tumor,yellow pericarp,white tendril and variation of seed shape,and the total variation rate is 16.13%.Typical mutant lines are H18S6,H18S14,H18S15,H18S619,H18S21,H18S24,H18S25,H18S30,H18S32,etc.The phenotypic identification of M₃ homozygous lines showed that the seed epidermis was pale yellow,the seed shape was oval,the seed shape was near circular,and the seed was deformed.