Penetration and Expression of the npnd Gene of Voltinism in F₁, F₂ and BCP Hybrids between Monobivoltine and Polyvoltine Tropical Strain of Silkworm (Bombyx mori L.)

P. TZENOV, Y. LAZAROV and Y. NACHEVA

Sericultural Experiment Station, BG-3000 Vratza, Bulgaria

Abstract

TZENOV, P., Y. LAZAROV and Y. NACHEVA, 2000. Penetration and expression of the npnd gene of voltinism in F₁, F₂ and BCP hybrids between monobivoltine and polyvoltine tropical strain of silkworm (Bombyx mori L.). Bulg. J. Agric. Sci., 6: 579-582

Studies were carried out at the Sericultural Experiment Station on the penetration and expression of the gene of voltinism npnd (nonpigmented and nondiapaused egg) in F₁, F₂ and BCP hybrids between the monobivoltine strain Super 1 and polyvoltine tropical strain Bonde 517. Egg incubation and rearing of hybrids and pure strains were carried out under a regime, provoking laying of nonpigmented and nondiapaused eggs.
The penetration of npnd gene (percent of layings with manifestation of npnd gene) in the tropical polyvoltine strain Bonde 517 was 90.10% and in the monobivoltine strain Super 1 – only 27.18%. The tropical strain Bonde 517 demonstrated also higher gene expression (percent of nonpigmented and nondiapaused eggs per laying) – 57.50% vs. 43.16% for Super 1 strain. The inheritance of the npnd gene penetration and expression in F₁ is intermediate. In backcrosses, npnd gene penetration is higher in the case of domination of the tropical strain blood.

Key words: gene penetration, gene expression, silkworm, monobivoltine tropical strain, polyvoltine tropical strain