Difference analysis of strength and elongation among cocoon filaments of silkworm races and application evaluation of breeding material

【Objective】Strength and elongation variation among different silkworm(Bombyx mori) varieties were studied to provide references for screening breeding materials of silkworm. 【Method】Two grains with identical cocoon width of48 varieties of silkworm cocoon were selected. Strength and elongation of per hundred HUI at the same place in cocoon filament were tested. Using SPSS 17.0 software, breaking strength, breaking elongation and the intensity of cocoon filament were compared among cocoon filament of different varieties of silkworm and a cocoon filament with better elongation was confirmed in the same breed. Lastly, breeding materials were evaluated. 【Result】Among 48 silkworm races, the least and the largest breaking force was 10.5 and 18.3 CN, respectively. The breaking elongation size ranged from 1.76 to 2.73 mm.The least strength and largest strength was 3.13 and 5.46 CN/dtex, respectively. Breaking strength, breaking elongation and intensity varied in different cocoon layers in the same species. The range of 300-600 revolutions displayed better strength and elongation. Variance analysis on breaking elongation of 300-600 revolutions of 48 varieties showed that 2, 5,1, 6, 12, 9, 3,4,18 and 21 had better elongation with elongation rate of over 26% and they were significantly different from other varieties(P0.05). 【Conclusion】300-600 revolutions of 48 varieties have better strength and elongation. Living pupa and reeling silk should be synthetically considered in evaluating breeding materials, through which silk can be utilized more widely and better silkworm cultivars can be bred.