ANALYSISES OF GENE EFFECTS ON SOME COCOON CHARACTERS IN SILKWORM MORIL

1.Estimates of genetic variance and covariance for individual characters showed that cocoon weight was controlled by both gene direct effect and maternal effect;Cocoon shell weight was controlled by gene direct effect mainly;Cocoon shell ratio was mainly due to maternal effect and se x-linked effect.2.Estimates of genetic covariance components of each pair of ch aracters indicated that there were high significant positive relationships among most of genetic effects except maternal additive effect in cocoon weight and cocoon shell weight.There was a high positive relationship idirect effect between cocoon weight and cocoon shell ratio,but in cytop lasm effect and maternal effect were high negative relationships between them.Also there were high positive relationships in direct effect and maternal dominance between cocoon shell weight and cocoon shell ratio.3.Predictions of gene effects pointed out that sex-chromosome effects （Σi8=1Lii） on cocoon weight and cocoon shell weight both were lar ger positive values,that means cocoon weight and cocoon shell weight of females are generally higher than those of males in Silkworm. Standardized donmiance directions of direct effects on cocoon weight and cocoon shell weight were high positive values,but standardized domiance directieon of maternal effects on both of them were high negative values,it showed the two characters had larger heterosis in F1 generation and depressed in F2 generation.Sex-chromosome effect （Σi8=1Lii） on cocoon she11 ratio was high negative value,explaining that females usually have lower cocoon shell ratio than males.Standardized domiance directions of direct effect and maternal effect on cocoon shell ratio were not significant,predicting that the heterosis of cocoon shell ratio in F1 generation is not obvious comparing to cocoon weight and cocoon shell weight.