Studies on the Induction of 2n Gamete in Chinese Cabbage and the Production of Tetraploid by Sexual Polyploidization Studies on the Induction of 2n Gamete in Chinese Cabbage and the Production of Tetraploid by Sexual Polyploidization Molecular Clon ing and Sequence Analysis of GLDH Gene cDNA from Brassica campestris ssp. chinensis Molecular Clon ing and Sequence Analysis of GLDH Gene cDNA from Brassica campestris ssp. chinensis Cloning and Sequence Analysis of Beta-1,3-glucanase Gene cDNA in Brassicacampestris ssp. chinensis Genetic Differentiation of Non-Heading Chinese Cabbage (Brassica campestris ssp. chinensis Makino) Germplasm Based on SRAP Markers