| Cucumber(Cucumis sativus L.)is one of the top ten vegetable crops in the world,which have a variety of nutrients,loved by consumers.Cucumber mitochondrial DNA appears as a strict paternal inheritance.Compared with other plant mitochondrial genomes,cucumber mitochondrial genome is big,and rich in polymorphism.Mitochondrial DNA fingerprints are constructed according to the polymorphism of mitochondrial DNA.It is equally important for species identification,genetic diversity study,seed purity analysis,and genetic relationship analysis.In particular,for mitochondrial paternal genetic species,it can quickly detect the purity of hybrid seeds and track pollen sources.The research on the related traits of cucumber fruit mainly focused on the fruit length,the wax powder on the surface and the fruit flesh color.However,the research on the genetic analysis of seed-cavity is rarely reported.Seed-cavity color is one of the quality traits of cucumber fruit,which has a certain effect on the performance of cucumber fruit.Therefore,it is of great significance to master the genetic rule of cucumber fruit.In this study,the mitochondrial DNA fingerprints of cucumber were constructed based on the maternal genetic characteristics of cucumber mitochondrial genome,and the genetic pattern of cucumber seed-cavity was studied.The main results were as follows:1.Construction of Mitochondrial DNA fingerprinting on Cucumber1)The markers were developed according to the mitochondrial genome sequence of cucumber.Out of the 69 pairs of primers,13 pairs were screened which exhibited higher polymorphism and clear bands.Each pair of the primers could detect 1-3 polymorphic bands,total 26.The band size was between 100-500 bp.Different combinations of primers could be used to identify 21 materials.Alleles amplified among the primers ranged from 2 to 4.The average of effective number of alleles was 1.818.The PIC values varied by each pair of primers ranging from 0.169 to 0.551.The average of Shannon's information index(1)was 0.69.Cluster analysis revealed that the 21 varieties could be clustered into 4 groups using a genetic similarity coefficient threshold of 0.71.The clustering results were nearly consistent with the ecological classification.2)Based on the DNA fingerprint of parent material,the seeds of 'Nanshui 3' were detected by primer mtSSR4.The result indicated that,67 seeds were consistent with the band of male parent,which were true hybrid seeds.3 seeds were consistent with the band of female parent,which were not.The purity of molecular markers identified was 95.7%,which were consistent with the field.Therefore,the constructed mitochondrion DNA fingerprinting of the cucumber variety would provide a new technical guidance for the purity identification of the hybrid such as 'Nanshui3'.2 Genetic Analysis of Seed-cavity Color Traits in CucumberWe used two inbred lines with different seed-cavity color(14401Fx14405F)as the parent materials.The seed-cavity of 14401F was white.The seed-cavity of 14405F was green.This research explored the inheritance of cucumber seed-cavity color traits with the method of six genetic(PI,P2,B1 B2,F1 and F2)populations conjoint analysis.Seed-cavity color traits of cucumber were controlled by two major genes and appropriate for the model of two major genes with additive-dominance-epitasis(model B-1).The C value of major gene heritability in F2 is 68.85%,which is higher.However,the environmental effect is 31.15%,which is lower.The selection of cucumber green seed-cavity color should be done at the early stage of separation during breeding.The color of seed-cavity was measured by visual and colorimeter.The seed-cavity of F1 showed light green,which was between two parents.The seed-cavity of F2 was separated.The C value of the heart cavity of each plant showed a bimodal normal distribution.According to this,we inferred that green of seed-cavity on the white is not completely dominant.Seed-cavity of cucumber is a quantitative trait,which may be affected by 2 pairs of major genes... |
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