Manifestation of Heterosis and Inheritance of Productive Characters in Simple and Complex Silkworm Bombyx mori L. Hybrid Combinations
II. Shell Weight and Shell Ratio

1 Institute of Animal Breeding, BG-2230 Kostinbrod, Bulgaria
2 Agricultural Firm “Agromier SAE”, Eg-11211 Cairo, Egypt


PETKOV, N., Z. PETKOV and H. GREISS, 2003. Manifestation of heterosis and inheritance of productive characters in simple and complex silkworm Bombyx mori L. hybrid combinations. II. Shell weight and shell ratio. Bulg. J. Agric. Sci., 9: 385–389

An investigation of heterosis manifestation and the inheritance of shell weight and shell ratio characters at simple and complex silkworm Bombyx mori L. hybrid combinations has been carried out at Sericultural Experiment Station Vratza at spring and summer seasons during the period 1997–1999. Distinct manifestation of heterosis was determined in F1 toward MP and HP for shell weight character in all tested simple and complex crosses, while determined heterosis manifestation for shell ratio character was insignificant and statistically unproved in 9 crosses toward MP and 7 crosses toward HP. Genetic parameters for degree of dominance in F1 (hp1) and F2 (hp2) showed that heterosis at shell weight is due to over-dominance (hp1 > 1) and epistatic gene interactions (hp2 < hp1). Relatively the most important epistatic gene interactions were (dd) and (aa), and from the two types of gene effects, (d) caused higher value of character.

Key words: heterosis, heritability, shell weight and shell ratio