Studies On AFLP And SCAR Molecular Markers For Cucumber Quality Traits

Cucumber (Cucumis sativus L.) is a kind of annual diplontic rattan plant, with the highest yield under protective cultivation, which is usually cross pollinated and is one of currently 10 series widely cultivated vegetables. The traditional breeding methods can only select from the phenotype not from genotype or molecular level. And the phenotype is the result of the interactions between genotype and environment. The phenotypes of the same genotype differ in every generation because the environment in every generation is not totally unanimous. So a large number of cucumbers have to be planted as possible as we can in the traditional breeding for obtaining the better genotype. The traditional breeding is a very useful method but it is too difficult to breed better variety with optimum genotype combination. Therefore the breeders have been searching for new breeding ways. In recent years, with the development and application of molecular biotechnology, the marker-assisted selection can make up the traditional breeding method, which is very important for the marker-assisted selection of cucumber. The breeders pursue on a well quality traits variety all along , But as a result of the cucumber quality traits basis complexity and the research lag, it is difficult to breed well quality traits and takes time long. The development of Mark-assisted selection shorted the time of traditional breeding. If a molecular marker with close linked to quality traits loci had been obtained, we can select or shift well quality traits fast and accurately, shorten breeding time and accelerate the acquisition of well quality traits with marker-assisted selection. Meanwhile, the molecular marker closed linked to quality traits will lay the foundation on cloning this gene which controlling quality traits traits and further researching for cucumber molecular mechanism.An AFLP systerm was established by two self-bred cucumbers with reverse quality traits , obtained a molecular maker close linked with quality traits and transferred it into SCAR maker. The main findings as follows: 1. Obtained high quality cucumber genomic DNAThe single plant genomic DNA extracted by the improved CTAB method and dissolved with T₁₀₁ and 1% agar gel electrophoresis showed that genomic DNA size is 23kb around.2. Established a fit cucumber AFLP analysis systemAn AFLP analysis system was established with cucumber by optimizing some factors of AFLP technological system. The results showed that the dosage of template DNA should be 100ng in a 25μL systerm and the products of preamplification should be diluted to 30 times.3. Obtained 79 polymorphic bands from 64 primer-combinationsThe AFLP fingerprinting of 2 cucumber materials amplified by 64 primer-combinations have been obtained. Every primer combination got 70—100 clear bands averagely, and 79 of them were polymorphic. There were 8 primer combinations' polymorphic bands more than 6.4. Cloned two bands from polymorphic bands and compared in NCBICloned and sequenced two bands from 79 polymorphic bands.Compared the sequenced result in NCBI bank.The result show that the 363bp, named V7T3A₃₆₃. One is a new find band in cucumber and the 181bp one is consistent with part of cucumis sativus ATP synthase beta subunit (atpB) gene, named V7T5A₁₈₁.5. Transfer AFLP markers of V7T3A₃₆₃ and V7T5A₁₈₁ into SCAR markersDesighed two pairs of PCR primers from the sequenced result. Amplificate it in F₂ generation show that the genetic distance from V7T3A₃₆₃ to the green/ miscellaneous color trait of cucumber pericarp is 36.36cM and to the blare trait of cucumber pericarp is 34.09cM.It also show that the genetic distance from V7T5A₁₈₁ to the green/ miscellaneous color trait of cucumber pericarp is 13.64 cM and to the blare trait of cucumber pericarp is 9.09cM.