Comparative studies of pupation rate, cocoon weight, reelability percentage and number of hatching among single cross, double cross and poly cross of silkworm
2004
Iida, N. (Dainippon Silk Foundation, Ami, Ibaraki (Japan). Inst. of Sericulture) | Tsurui, Y.
The usability of two Poly Cross, "(Asa.Hi x To.Kai) x (Kinshu x Shouwa) (A x K)" and " CKinshu x Shouwa) x(Asa.Hi x To.Kai) (AxK)" of silkworm was studied. Although there was no significant varietal difference among single cross, "KinshuxShouwa", double cross, "Asa.Hi x To.Kai" and Poly Cross, whose pupation rates, cocoon weights and reelability percentages were investigated this time, from the integrated evaluations of these three items, the evaluation of Poly Cross did not exceed those of single cross or double cross for any rearing season. The number of eggs laid and number of hatchings of Poly Cross 'K x A' are significantly larger than those of Poly Cross ' A x K' for any rearing season, and ' K x A' showed its superior value in the property of egg laying, but' A x K', the reverse crossing, was inferior. From the above results, it is considered that, in order to put Poly Cross into practical use, it should be tested though a number of crossing and its high combining ability should be confirmed. However, if a diversification of a breed proceeds, the uniformity of its phenotype decreases among the group. Although a heterosis is recognized only in F1, it decreases dramatically in F2 and in everything following. Thus, it is said that the method similar to F1 is preferable for the crossing of plural hybrids. Therefore, in the countries where the main target is to promote the income of sericultural industry, it is desirable to proceed with the breeding leading to the improvement of the property of egg laying , amount of cocoon crop and reelability percentage, aiming at breeding the strain with good health suitable to the local environments using the heterosis within double cross.
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