Manifestation of Heterosis and Inheritance of Productive Characters in Simple and Complex Silkworm Bombyx mori L. Hybrid Combinations
III. Filament Length and Filament Weight

1 Institute of Animal Science, 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. III. filament length and filament weight. Bulg. J. Agric. Sci., 9: 527–532

An investigation of heterosis manifestation and the inheritance of filament length and filament weight characters in simple and complex silkworm Bombyx mori L. hybrid combinations has been carried out at Sericultural Experiment Station Vratza during spring and summer seasons of 1997–1999. Distinct manifestation of heterosis in F1 toward MP was determined for filament length in the range of 7.48–15.62 % for spring and 4.98–6.37 % for summer rearing season and 6.96–10.11 %, 5.15–11.68 % for filament weight in all tested simple and complex F1 crosses. Comparatively high manifestation of heterosis toward HP was determined too, respectively 6.29–15.17 % at spring and 4.39–5.42 % at summer rearing seasons for filament length and 0.93–7.75 %, 0.78–8.42 % for filament weight. In all cases, when heterosis in F1 was highly expressed, it was observed higher depression in F2. Genetic parameters for degree of dominance in F1 (hp1) and F2 (hp2) showed that heterosis for filament length and filament weight are due to over-dominance (hp1 > 1) and epistatic gene interactions (hp2 < hp1). Dominant epistatic gene interactions (dd) had relatively most important influence, followed by aditive-aditive epistatic gene interactions (aa) and from the two types of gene effects, dominant effect (d) was the most important and always positive for filament length, and caused its higher values.

Key words: silkworm, heterosis, heritability, filament weight and filament length