Studies on characteristics of genetical races of the silkworm, Bombyx mori
1998
Shimizu, K. (National Inst. of Sericultural and Entomological Science, Tsukuba, Ibaraki (Japan)) | Kosegawa, E. | Kikawada, T. | Okajima, T.
Two kinds of characteristics, larval dispersion behavior and production of double cocoons, were analyzed among silkworm genetic resources. First, comparatively active races in terms of dispersion behavior immediately after hatching were selected and recorded to obtain basic data for he characteristics of the genetic resources. One hundred nine races showed an active dispersion behavior. The active individuals accounted for only a part of the total number of larvae in all the races. This characteristic was not fixed by intra-race inbreeding carried out four times between individuals which showed the active dispersion behavior. Second, the frequency of production of double cocoons was also recorded to characterize the different silkworm races. This character was investigated three times and showed a high experimental reproducibility. Although the frequency of double cocoon production could be affected by changes in the seasons, the average percentages of double cocoons in each race were smatout in all the seasons. Three races, Koishimaru-Sanshi, Shinryukaku No.22 and Ryukyutasanken-Shizuoka, were independently used in intra-race inbreeding experiments between moths derived from double cocoons. After repeated inbreeding, the frequency of production of double cocoons did not increase significantly. As an additional experiment, the race, Ryukyutasanken-shizuoka which showed a high frequency of production of double cocoons was crossed to low frequency races. Tsunomata-Shizuoka race and Daizo-Nagano race, respectively. Subsequently, F1 hybrids showed an intermediate frequency of double cocoon production compared with their parents
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