Abstract
The Creeper (Cp) gene from the Jitokko was introduced into the inbred strains, WL-G and NG-A, and two strains Cp (WL-G) and Cp (NG-A) were established in the gradings by successive backcrosses.
In the Cp (NG-A) strain, heterozygous parents produced the expected homozygous Cp/Cp embryos, 83.2% of which was viable on the 10th day of incubation and in the Cp (WL-G) strain viable homozygous Cp/Cp embryos were not obtained. Although the Cp (NG-A) showed high percentage of viable homozygous Cp/Cp embryos, the percentage decreased as maternal ages increased.
