Genetic Analysis Of Carpopodium Length In Cucumber And Identification Of Its Quantative Trait Loci

Cucumber is one of the important vegetables, which have a closely relation with people's life. The carpopodium length is one of the most important trait, which affect the quality and economical value of cucumber. With the changes of people's consumption concept, the novelty and peculiar cucumber cultivar (short carpopodium or no carpopodium) become more and more popular in people's life. In this study, 150 F6 populations, derivied form a cross between greenhouse cucumber cultivar Z9 and Dongnong 129, were used to analyze the genetic regularity by the major genes plus polygenes mixed inheritance model and detect QTL which associated with carpopodium length of cucumber through the method of Bulked Segregant Analysis (BSA) and Sequence-Related Amplified Polymorphism (SRAP) marker, in order to provide the theoretical basis to the Molecular Marker-assised Breeding and the appearance improvement of cucumber. The main results as followed:1. The carpopodium length of cucumber fitted in E-2-6 inheritance model, which was two linked major genes plus polygenes model. The additive effects value of major gene was 0.36, the eptasis effects value was 0.69, the heritability value of the major genes and polygenes were 56.27% and 17.08%. It showed that the hereditary of carpopodium length in cucumber was mainly controlled by major genes, which influenced by additive effects and eptasis effects, and carpopodium length was greatly affected by environment factors.2. The segregation survey of carpopodium length in F6 population showed that the data of carpopodium length was changed continuously, and fitted in a normal distribution in the F6 population, which indicated that carpopodium length of cucumber was quantitative trait.3. The genome DNA of cucumber was extracted by the method of improved CTAB, the results showed that the genome DNA was integrity, and had a higher quality after the detection of 1% agarose electrophoresis.4. A stable cucumber SRAP-PCR reaction system was established by orthogonal design (25μL) including 10×PCR Buffer 2.5μL, 25mM MgCl₂ 1.4μL, Taq polymerase (2.5U/μL)0.2μL, template DNA 30ng, primer (0.1ug/μL)0.6μL, 2.5mM dNTP 2.5μL, ddH2O16.2μL.5. A total of 380 pairs of SRAP primers were screened between two parents, of them, 153 pairs of primers were polymorphic (the rate of polymorphism was 40.3%). The long /short carpopodium DNA pools were constructed, and 153 pairs of primers were screened between two gene pools, the results showed that 27 pairs of primers could produce clear and stable bands (the rate of polymorphism was 17.6%). This 27 pairs of primers were used to screen 20 individuals, which composed the two gene pools; the results showed that 16 markers were polymorphic which could analyze in F6 population. Among them, 9 markers were polymorphic in 150 F6 population individuals. Of these 9 markers, 7 polymorphic markers basically fitted in 1(Z9):1 (Dongnong 129) based on chi-square test.6. QTL, which associated with carpopdium length, was identified through the method of composite interval mapping. Two QTL, which control carpopdium length, were detected in 150 F6 population individuals. Of these two QTL, one QTL (Qcl1) which between ME11-EM4 and ME14-EM9, was located on limkage 1; Another QTL (Qcl2) which between ME10-SA7 and ME21-EM3, was located on limkage 2. Qcl1 and Qcl2 could explain 8.29% and 3.42% of phenotypic variation, respectively.