| Cucumber（Cucumis sativus L.） is one of important vegetables in China, and also is the mostpopular vegetable all over the world. The genetic background of cucumber crop is narrow. Butcucumber is regarded as the model plant for the sex expression research because of its sex type diversity.By now, scientists have got many sex expression related genes and partly revealed the mechanism of thepathway that controls the development of the cucumber sex differntiation by hormone. But it is stilldifficult to explain the diversity of the sexual types completely. This study will focus on the moleculargenetic basis of the sexual type diversity by association analysis, and find the relationship betweenDNA methylation and the stability of the cucumber sex types in order to understand deeply theregulating mechanism for sex differentiation and utilize effectively the germpalsm of the diverse sextypes in cucumber.In this study, we designed InDel primers based on the cucumber genome sequencing andre-sequencing, and analyzed the genetic diversity of the primary core germplasm from differentcountries and regions. According to the primary core germplasm, a phenotypic core collection wasselected. Based on identification of the node rate of the female flowers and molecular diversity ofphenotypic core collection, association analysis of the sex type related genes was done. The DNAmethylation of the germpalsm with different sex types treated with different hormones and differentconditions of temperature and light time was analyzed by MSAP method. The main results were asfollows：1.134pairs of InDel primers had been designed based on the cucumber genome sequencing andre-sequencing by the way of screening the insert/delete loci every1-3M bases on the whole genome.The results showed that clear and effective PCR amplification products were obtained from134pairs ofprimers. Among these primers,116primers were polymorphic, accounting for86.6%of the total andrevealed the genetic diversity and specificity of16typical cucumber germplasms. From them, sevenpairs of core primer could be used to construct the molecular ID of cucumber germplasm.2. Based on the genetic diversity analysis of473acccessions of primary core germplasm fromdifferent countries and regions which was conserved in the national midterm genebank of the vegetablegenetic resources,119pairs of polymorphic InDel primers were selected from134pairs of InDelprimers. It was shown that the Shannon s index of this primary core collection was0.0154-1.0526, thePIC was0.0043-0.5629, the genetic diversity was0.0043-0.6375. According to clustering analysis,473germplasm was divided into two groups, The first group cound be clustered into two subgroups, and thesecond group could be classified into five sub groups. Their source and phenotypes were similar in eachsubgroup. The phenotypic core germplasm including280accessioms of diverse germplasm wereselected and retained95.5%of the alleles of473germplasm.3. Analysis on population genetic structure of the280phenotypic core germplasm showed that3subpopulations had been identified, which included exotic subpopulation, south China type subpopulation and north China type subpopulation. Based on the value of Q resulted from the geneticstructure analysis, the InDel loci data and the phenotypic data of node rate of female flower in springand autumn of2008,spring and autumn of2009and the difference between spring and autumn everyyear, an association analysis between sex type and its related genes was carried out.20loci in2008spring,2loci in2008autume,16loci in2009spring,14loci in2009autume associated were gotrespectively, which had the value of P lower than0.01.And14loci in2008,10loci in2009wasassociated with the difference between spring and autumn. CuIn113, CuIn114, CuIn309was associatedwith the node rate of female flower in both two seasons.4. Four classic cuumber germpalsm：10SQT165（165）,5224G（5224）,08ABN28（BN）,9930weretreated with different hormones including5-azaC（5-Azacytidine,5a）, AgNO3（Ag）, ethephon（ETH）,water（CK）, and different conditions of temperature and light time including high temperature and longdaylight（HL）, high temperature and short daylight（HS）, low temperature and long daylight（LL）, lowtemperature and short daylight（LS） for40days from sowing seeds to transplanting. According to MSAPanalysis, the result showed that differet germplasm expressed different sensibility to differet treatments.As an unstablity germplasm,9930with unstable sex type in different seasons expressed highermethylation diverse level than other germplasm. After being treated with ETH and low temperaturerespectively, a higher node rate of female flower accompanied with a higher level of demethylation. Buta higher level of methylation exsited with the increace of male flower among the germplasm after beingtreated with AgNO3. It could be inferred that DNA methylation may promote the cucumber male flowerdifferentiation and DNA demethylation may be good foe the female flower differentiation. |
PDF Full Text Request