家蚕破风茧遗传学研究

STUDIES ON THE INHERITANCE OF PERFORATED COCOON IN SILKWORM (BOMBYX MORI)

采用数量遗传学的世代分析和综合方差以及协方差分析方法，对破风茧率的各遗传效应参数、广义和狭义遗传力以及破风茧率与万蚕收茧量等的相关系数进行了估算。结果表明，６个世代之间，破风茧率差异达极显著水平。其遗传性不符合加性—显性效应模型，而与加性—显性—上位效应模型相符。在６个遗传效应参数中，加性×显性的上位效应不显著。主要是中亲值和基因加性效应，其次为显性效应，上位效应较小。其中，显性效应和加性×加性的上位效应为负值。由于显性效应和显性×显性的上位效应符号相反，推测显性效应的互作主要是基因的重叠作用和显性上位作用。破风茧率的广义和狭义遗传力都较低，说明环境条件对破风茧的发生有较大的影响。因此，注意调节饲育和上簇的环境条件，对降低破风茧率有重要作用。广义和狭义遗传力相差不大，进一步说明在遗传因素中基因的加性效应起主要作用，显性效应较弱。破风茧率对万蚕收茧量和产卵量具有较大的负效应，而对结茧率的影响不显著。

Generation analysis and variance and covariance analyses in quantitative genetics were employed to estimate 6 genetic parameters and broadand narrowsense heritability of the character perforated cocoon and its correlation with cocoon crop per 10000 fourthinstar silkworms. Highly significant differences were observed between the 6 generations studied in their perforated cocoon rate. The inheritance of the character was found to fit well into the additivedominantepistatic model but not into the additivedominant model. Of the 6 genetic parameters studied, epistasis of additive dominant was nonsignificant. Midparent value and the additive effect of genes had the most significant effects, followed by dominance. Epistasis had a relatively small effect. The values of dominant effect and the epistatic effects of additive additive were negative. It is conjectured that the interaction of dominant effects consists mainly in gene duplication and dominant epistasis since the dominant effect value and the epist sresearch effect predictionasis value had opposite signs. Both broadsense and narrowsense heritability of the character perforated cocoon appeared to be low, suggesting that environment has a major effect on the occurrence of perforated cocoons, and adjusting the environment conditions for rearing and mounting will be effective for reducing perforated cocoon rate. The fact that no great disparity was observed between broadsense and narrowsense heritability shows that additive effects may play a predominant role among verious genetic factors and dominant effects are of secondary significance. Perforated cocoon rate had considerable negative influence on cocoon crop and egg deposition per 10000 fourthinstar silkworms while its influence on cocooning percentage was rather insignificant.