The Use of Parthenogenetic Clones to Create Highly Heterogeneous Hybrids of the Silkworm (Bombyx mori L.)

Abstract

Since the entire world's sericulture, to achieve maximum heterosis is based on the feeding of hybrids of only the first generation, therefore, operations for the preparation of pure hybrids are of particular importance. In Uzbekistan, the Sericulture Research Institute has developed new biotechnologies specifically to solve this problem, and genetically modified breeds and parthenogenetic clones have been created on their basis. The unfertilized eggs are thermally activated at t = 46°C for 18 minutes, and the reducing division of meiosis in the germ cells of the silkworm is hampered. As a result, the eggs remain with a diploid set of chromosomes and develop as zygotes. Since silkworm females are heterogamous by sex chromosomes, only female parthenogenetic clones develop from thermally activated eggs. Clonal-breed hybrids, characterized by increased viability of caterpillars – 93,5-98,0% (in the control – 90,0%), the high cocoon shell ratio – 22,1-23,8% (in the control – 22,5%), increased egg-bearing capacity - 622-639 pcs (in the control - 630 pcs), metric number of thread - 3344-4065 units (in the control - 3321), the synchronicity of caterpillar development, uniformity of cocoons, ease of preparation. The technology of thermal activation of unfertilized silkworm eggs for parthenogenetic development is not particularly difficult, therefore clones can reproduce the required number of generations and in an unlimited number of individuals. The second component for hybridization can be males of almost any breed. Clones, due to their genetic constancy, do not need breeding and breeding selection, they do not need to be divided by gender, because they are represented by only one female sex, and have high combinational ability and amicable development.