A PRELIMINARY STUDY ON THE POLYMORPHISMS OF ISOZYMIC LOCI IN GRASS CARP (CTENOPHARYNGODON IDELLUS)

The genetic variants of six isozymic systems (LDH, MDH, ADH, GDH, IDH, and EST) encoded approximately by 18 to 23 presumptive loci in 25 individuals of grass carp taken from the same locality were detected through vertical slab starch gel electrophoresis and subsequent specific histochemical staining techniques. Polymorphisms were observed at seven loci (s-Mdh-A, Adh-B, Gdh-1, Gdh-2, Est-1, Est-6, and Est-14), The observed frequencies of genotypes at four polymorphic loci (s-Mdh-A, Adh-B, Gdh-1, and Est-1) are all in accord with the Hardy-Weinberg's law of genetic equilibrium. Our results show that isozymic loci of grass carp possess obvious polymorphisms and indicate that there are possibilities of artificial selective breedings and directional breedings for grass carp.The genetic and molecular bases of GDH and EST isozymes of grass carp and the mechanisms in relation to the variation of enzymes are discussed.