2009 Volume 78 Issue 2_3 Pages 2_3_151-2_3_159
The genetic characterization of the cocoon color of the silkworm Bombyx mori is little known, because the cocoon color formation is entangled with various complicated factors, such as pigments synthesis, pigments transport, 1ight reflexivity etc. However, the silkworm is appropriate to study on the genetics of the cocoon color, since there are many known mutants. We found that the green cocoon color strain, Ryokuken ichi-go was composed by two factors: 1) greenish yellow color (Gy) , 2) fluorescent color (Fy) enhanced by ultraviolet light. This finding was observed for the first time under the black light. To investigate the genetics and gene mapping about Fy and Gy, the original strain (G01) of Ryokuken ichi-go was crossed with the strain RF02 whose cocoon color is white and no enhanced fluorescent color under ultraviolet light. The cocoon color of F1 were nearly same color to the strain G01, so these greenish yellow color and fluorescent color of the cocoon seemed to be dominant characters. Then F1 was backcrossed to the strain RF02 and the individuals of this BF1 were segregated to four kinds of cocoon color phenotypes. These results confirmed that these two kinds of cocoon color, greenish yellow and fluorescent color, were independent dominant characters. Gene mapping for Gy and Fy were carried out by RFLP. We report here that Gy is located at 5.4cM from a marker m72 on the chromosome RFLG5 and Fy is located at 7.5cM from a marker e96 on the chromosome RFLG20.
