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.

The purpose of the work was to evaluate the breeds of the world silkworm collection of the Scientific Research Institute of Sericulture (SRIS) labelled by sex at the stage of eggs of silkworm by biological characteristics for their use in hybridization. The eggs of silkworm of these genetically modified breeds can be easily separated by color (by sex) before reaching the imago stage. The work was carried out in the laboratory of genetics and breeding of the silkworm of the SRIS on the materials of the living collection of the silkworm in 2020-2022. The search and selection of breeds for hybridization was carried out by the ranking method. The ranking method consists in the ability to establish a relationship between the features, which are expressed by the order of the place occupied by each member in the aggregate, i.e. the place of rank in the variation series. Hybrids from breeds labeled by sex at the stage of silkworm eggs with 100% purity of preparation, with the maximum manifestation of heterosis in reproductive and biological indicators, differ in: a high number of normal eggs in a clutch of C-12×C-10 - 614pcs, C–5×C-13 - 598pcs, C-12×C-14 – 598 pieces; caterpillar viability – C-12×C-10 – 96,5%, C-5×C-13 – 96,0%, C-12×C-14 – 96,2%; content of raw silk, – C-12×C-10 – 22,2%, C-5×C-13 – 22,0%, C-12×C-14 – 20,3%. By the methods of traditional breeding selection at all stages of development, improved lines of silkworm breeds C-5, C-10, C-12, C-13, C-14 were bred in terms of reproductive indicators, hatching of silkworm eggs, the viability of caterpillars, weight and content of raw silk of cocoons.