title: A complementary method for production of tetraploid Crassostrea gigas using crosses between diploids and tetraploids with cytochalasin b treatments.
abstract: We present a new method to produce tetraploid Crassostrea gigas by cytochalasin B inhibition of polar body 2 expulsion in diploid females crossed with tetraploid males. This offers a means of direct introgression of genetic characters from selected diploid to tetraploid lines, avoiding a triploid step. Offspring larval ploidy shifted over time and depended on size, with tetraploids more frequent among the smaller larvae and triploids among the large. Viable tetraploids were found at 4 and 6 months, indicating the technique was successful. The possibility that gynogenesis occurred was tested by microsatellite analysis to confirm the presence of paternally inherited alleles. These were present in all animals of the 2n x 4n + CB (female first) cross. However, a 4n x 2n + CB cross produced triploids, including some gynogens. Our method illustrates for the first time that diploid C. gigas eggs, if selected for large size, can give viable tetraploid offspring.
authors.affiliation: Institut Français pour la Recherche et Exploitation de la Mer, Laboratoire d' Génétique et Pathologie, La Tremblade, 17390, France, hmccombi@ifremer.fr
authors.forename: Helen
authors.initials: H
authors.lastname: McCombie
authors.forename: Christophe
authors.initials: C
authors.lastname: Ledu
authors.forename: Pascal
authors.initials: P
authors.lastname: Phelipot
authors.forename: Sylvie
authors.initials: S
authors.lastname: Lapègue
authors.forename: Pierre
authors.initials: P
authors.lastname: Boudry
authors.forename: André
authors.initials: A
authors.lastname: Gérard
mesh_terms: D000818:Animals; D001947:Breeding / Q000379:methods*; D003433:Crosses, Genetic; D003571:Cytochalasin B / Q000494:pharmacology*; D018895:Microsatellite Repeats / Q000235:genetics; D010125:Ostreidae / Q000235:genetics*; D010063:Ovum / Q000187:drug effects*; D011123:Polyploidy; D013997:Time Factors
chemical_list: D003571:Cytochalasin B