家蠶育種의 最近의 進步

Recent Advancement in Silkworm Breeding

There are far less breeders and research institutes in our country than those in Japan. In the field of sericultural industry, well developed country, Japan has not made a reasonable development in silkworm breeding science due to no exchange of new breeding technique and new idea. Therefore it is quite natural that most Korean breeders have experienced in the difficulty of silkworm breeding because of no information from other countries. However the silkworm variety belongs to well improved organism like other animals and plants. 1. On the basis of productivity in 1960 the amount of cocoon production per 10 a increased by 2.3 times, the amount of raw silk per 10 a by 2.7 times, and the amount of cocoon production per box by 1.9 times in 1976. These increases seem to result from newly improved silkworm varieties and stability of silkworm rearing. As shown in table 2, the length of a cocoon filament has increased by 46 per cent and the percentage of raw silk by 23 per cent. These characters are closely related to the hereditary phenomena of a variety. 2. At present time, twenty-two silkworm varieties almost equal to the productivity of Japanese varieties are authorized and being extended to the farmers. Of those varieties, 12varieties were improved at Sericultural Experiment Station and 10 varieties at Private Research Institutes. 3. In general the resistance of male and F₁ hybrid to the diseases is stronger than that of female and original parent respectively. In order to remove the week point of original parent the double cross or three way cross is being used. 4. The hereditary phenomena of a few virus resistances disclosed recently will be applied to the silkworm breeding. 5. Complete resistance to Ina-virus was inherited by a recessive major-gene and possibility of its application to the breeding is broadly discussed. 6. The silkworms fed on the artificial diet are known to be susceptible to virus and Streptococcuss faecalis. 7. The resistant strains to high temperature, humidity and nutritive deficiency have been required up to the present time. Optimum conditions were able to be set up for resistance test of a variety and selection of a new silkworm strain. There are still problems, such as the resistance to low temperature and sudden change of temperature. 8. In our country the young silkworms are being fed on the artificial diet in large scale. Simultaniously with this application of artificial diet, new variety suitable to the artificia1 diet is urgently required. 9. Newly hatched silkworms have no close relation to the component change of improving artificial diet in their feeding response and growth. This finding suggests that the breeding for a suitable strain to the artificial diet can be started at any time. 10. Feeding responses to the artificial diet become better gradually every generation. Maximum feeding responses are usually found in 4th generation. 11. Individual selection for Bombyx mori can be carried out as using l% chromic oxide for test of digestibility of a larva. Thus the productivity of soil may be incerased. 12. Male and female can be easily discriminated by the difference of larval marking, egg color and cocoon color which were obtained in a complex translocation between Z(autosome) and W chromosmes.