Cloning of 6-phosphoglucona te Dehydrogenase Gene (6PGDH) and Molecular Confirmation of Allotetraploid in Cucumis Molecular Cloning and Functional Analysis of a 6-phosphoglueonate Dehydrogenase Gene Md6PGDH1 in Apple Cloning of 6-phosphoglucona te Dehydrogenase Gene (6PGDH) and Molecular Confirmation of Allotetraploid in Cucumis