| The silkworm, Bombyx mori, is one of the important economic insects and it has had a history of more than 5000 years being reared in China. The purpose of rearing the silkworm is for obtaining good silks. Studies on genetics and application in silkworm dated back nearly one hundred years, so abundant experiment of study on genetics and application in silkworm has been accumulated. And abundant silkworm resources have been collected. The study on genetics of silkworm facilitates the technology of silkworm breeding. Abundant experience of the persons who work for breeding, manpower and material resources are needed to improve on the commercial varieties while the traditional breeding method is applied. With the improvement of the technology of breeding, the method of "breeding in pairs" that two strains becoming one of mating are selected and bred separately and that the hybridized combination of them is tested while they are selected and bred in the 5th or 6th generation and that the cross combinations are obtained in the 11th of 13th generation, was founded in the 1960s. The result of silkworm's traditional breeding method is improved partly by using the method of "breeding in pairs". The Production efficiency of cocoon has been increased significantly by the shell ratio rising from native race's 10% to common race's 25%. However, the traditional breeding method can only select from the phenotype not from genotype or molecular level. And the phenotype is the result that interacts between genotype and environment. The phenotypes of the same genotype disagree in every generation because the environmental condition rearing the silkworm in every generation is not totally unanimous. A large number of silkworms have to be reared as possible as we can in the traditional breeding for obtaining the better genotype. The traditional breeding is a very useful method but it is too difficult to breed a best variety containing the best genotypes. The silkworm breeders have been searching for new breeding ways to find the best genotypes. The marker-assisted select that can equalizethe tradition breeding method is found with application and development of bip-tech. The marker-assisted, select is a novel breeding method that can component the traditional breeding. It is very important that the marker-assisted select of silkworm is carried on. Constructing a linkage map and quantitative trait loci (QTL) are essential foundation for the marker-assist select. An AFLP (amplified fragment length polymorphism) linkage map was constructed with p50 race and C100 race in this study. The ways of constructing AFLP linkage map were discussed and the QTLs of quantitative traits for whole cocoon weight, shell weight, pupa weight and shell ratio.1 Constructing the linkage mapTwo silkworm races, DaZao(p50)and C100(871)that their ecotype differs greatly, were used in the experiment. DaZao that its economic trait is relatively bad and that its cocoon color is green is a common race for constructing linkage map and harbors a Gc gene. The Gc gene (gene of green cocoon color) locates in 15th chromosome. C100 that its economic trait is relatively excellent and its cocoon color is white is a commercial race. The 44 individuals from BC1 generation at random, among them green cocoon and white cocoon each 22, the male and female each 11 for green and white cocoon, were used.1.1 Constructing of an AFLP linkage map of silkworm8S22 bands were amplified with 96 pairs of selective amplified primer. Every primer set can amplify 88 bands on average. The polymorphic bands were 5204 bands among 8522 and the polymorphic bands on average was 54. There are 1744 loci fitting for 1 : 1, 1474 single loci and 2431 loci belonging to segregation distorter, which the proportion of segregation distorter is 46.7%.133 linked groups and 327 unlinked loci consist of 1474 loci after software analyzing with QTXbl9 (Version0.29)(2003). 35 linked groups that each group contains 10 loci at lest make up an AFLP linkage map of silkworm. 806 loci build up 35 link...
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