Heterosis, Depression and Dominance Rates for the Indexes Length and Within-cocoon Unevenness of the Silk Filament in Silkworm Hybrids (Bombyx mori L.)

Y. NACHEVA, N. PETKOV and P. TZENOV

Sericultural Experiment Station, BG-3000 Vratza, Bulgaria

Abstract

NACHEVA,Y., N. PETKOV and P. TZENOV, 2000. Heterosis, depression and dominance rates for the indexes length and within-cocoon unevenness of the silk filament in silkworm hybrids (Bombyx mori L.). Bulg. J. Agric. Sci., 6: 485-488

A study of the heterosis effect in F₁, depression in F₂, dominance rates in F₁ and F₂ and the gene effects in the inheritance of the indexes length and within-cocoon unevenness of the silk filament in F₁, F₂ and BCP hybrids of the races Super 1, Ogosta 2 and Kom 2 was carried out at the Sericultural Experiment Station in Vratza.
It has been established that the indexes length and within-cocoon unevenness of the silk filament demonstrate heterosis effect in F₁ and depression in F₂.
The increase of the average values of the index within-cocoon unevenness of the silk filament in F₁ accounts for the lower evenness of the filament.
The indexes length and within-cocoon unevenness of the silk filament are inherited by the type of positive superdominance (h₁ > 1).
The dominant-dominant (dd) and additive-dominant (ad) epistatic genes as well as the dominant gene effects (d) are relatively most important for the inheritance of the indexes length and within-cocoon unevenness of the silk filament.

Key words: heterosis, depression, dominance rates, silkworm hybrids