• International Journal of Industrial Entomology and Biomaterials
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• v.4 no.2
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• pp.149-153
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• 2002

Induction of non-diapause eggs and manifestation of quantitative characters were studied in different seasons by low temperature incubation of eggs of a low yielding diapause with coloured cocoons silkworm breed, RDI of Bombyx mori. Hundred percent of nandiapause eggs were induced when the egg incubation was carried out at 15$^{\circ}C$ followed by incubation initially at $25^{\circ}C$ and then at $15^{\circ}C$. The diapause-nondia-pause relation was found to be reversible. Analysis of variance study demonstrated significant variation in all the quantitative characters whereas significant variation due to different incubation treatments was observed for larval span, fifth instar larval span, cocoon yield/10,000 larvae by weight, cocoon weight, cocoon shell weight, and cocoon shell ratio. study on hybrid vigour skewed significant heterosis over mid parent value for four economic characters viz., cocoon weight, cocoon shell weight, cocoon shell ratio and filament length in a Fl hybrid between RD1 with diapause eggs and Japanese type bivoltine $NB_{4} D_{2}$.

• Journal of Sericultural and Entomological Science
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• v.39 no.2
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• pp.205-209
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• 1997

In a line X tester crossing programme (24 lines 2 testers) the general combining ability (GCA) and specific combining ability (SCA) effects were analyzed for five economic characters in the bivoltine silkworm, Bombyx mori L. The results showed desired GCA effects in 934D1 (9500), 934B (9789) and 934A1 (9855) for cocoon yield per 10,000 larvae brushed by number. Likewise, the lines found to be superior based on GCA effects for other characters were as follows; 931D (14.040 Kgs), 935E (17.023 Kga.), 934D1 (15.643 Kgs.) and 934B (15.687 Kgs.) for cocoon yield by weight: 931D (1.717 g) and 930E (1.796 g) for single cocoon weight; 932B (0.330 g) for single shell weight: 931D (1.717 g) and 930e (1.796 g) for single cocoon weight; 932B (0.330 g) for single shell weight; 932B (18.7%), 933A (18.86%) and 935A (19.89%) for shell ratio. SCA effects showed the superiority of 932D$\times$KA (9822 cocoon yield per 10,000 larvae brushed by number); 932A$\times$NB4D2 (16.933 Kgs. cocoon yield per 10,000 larvae brushed by weight); 931C$\times$KA (1.911 g single cocoon weight); 934$\times$NB4D2 (0.371 g single shell weight and 21.0% shell ratio). The analysis indicated non-additive gene action for all the five characters.

• Journal of Sericultural and Entomological Science
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• v.31 no.1
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• pp.20-24
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• 1989

The purpose of this experiment was to obtain the basic information on heterosis and inbreeding depression of quantitative characters in the silkworm by diallel crosses of seven varieties differing widely in each character. Period of 5th instar cocoon weight, cocoon layer weight, cocoon layer ratio, boiling off ratio, raw silk percent, bave length, bave weight, bave size, weight of first molting larva and fourth molting larva were investigated. The results obtained were summarized as follows : The degrees of positive heterosis of cocoon weight and cocoon layer weight were higher. Period of 5th instar and boiling off ratio were negative heterosis. In F1 generation, cocoon weight and bave weight showed positive heterobeltiosis, while fifth instar-period, cocoon layer ratio and boiling off ratio showed negative heterobeltiosis in the F1 and F2 generation. Inbreeding depression was observed in cocoon layer ratio and boiling off ratio.

• Journal of Sericultural and Entomological Science
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• v.9
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• pp.35-38
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• 1969

This study was carried ont to investigate the effect of feeding amount on the metric characters of silkworm at each day of 5 th instar. The results obtained from the study are summarized as follows: 1. The increased amount of feeding did not affect on the metric characters except the character, number of cocoon per litre, by each day of 5 th instar. 2. The decreased amount of feeding did affect the weight of cocoon, weight of cocoon layer and did not affect the pupation, best cocoon rate, cocoon layer rate and number of cocoon per litre by each day of 5 th instar. Namely, the weight of cocoon or weight of cocoon layer was decreased by 12 to 17 per cent in decreasing amount of feeding through 5 th instar. Weight of cocoon or cocoon layer decreased by 5 per cent in the decreasing amount of feeding at just 7 th day of 5 th instar.

• Journal of Sericultural and Entomological Science
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• v.31 no.1
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• pp.25-36
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• 1989

In this experiment, gene action were analyzed for seven silkworm varieties in order to obtain basic information on their genetic improvement by diallel crosses. The results obtained were summarized as follows : In F1 generation, over-dominance was shown by Vr-Wr graphic analysis in four characters such as cocoon length in female, bave weight, cocoon weight and boiling off ratio in both male and female, and partial dominance in four characters such as fifth instar period, cocoon layer weight, cocoon layer ratio and bave length. In F2 generation, the partial dominance in all characters were obtained. Components of genetic variance analyzed for five characters such as fifth instar period, cocoon width, cocoon layer weight, cocoon layer ratio and fibroin contents in F1 generation, and for four characters such as cocoon width, cocoon layer weight, cocoon layer ratio and frbroin contents in F2 generation showed that addition effects were higher than dominant effects.

• International Journal of Industrial Entomology and Biomaterials
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• v.7 no.1
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• pp.59-63
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• 2003

In the present study, hybrid vigour in terms of heterosis and over dominance of newly evolved bivoltine hybrids and their reciprocals raised from the promising newly evolved bivoltine breeds were calculated for the important parameters like pupation, cocoon yield, cocoon weight, shell weight, shell ratio, raw silk percentage, filament length and neatness. Through there was no significant difference among the hybrids for the characters pupation, cocoon yield and cocoon weight, the magnitude of heterosis and over dominance were varied significantly for these characters. However, significant differences were observed between new hybrids and control hybrid for the characters like cocoon shell weight, cocoon shell ratio, filament length and raw silk percentage. The results indicate that majority of new hybrids have shown higher heterosis and over dominance than control hybrid. The data also indicate that highest mean heterosis of all new hybrids was recorded for cocoon yield followed by filament length. Whereas highest mean over dominance was recorded for cocoon yield followed by cocoon weight. Negative mean heterosis and over dominance were recorded for the trait cocoon shell ratio. Based on the results, the importance of three hybrids viz., CSR2 ${\times}$ CSR4, CSR2 ${\times}$ CSR5 and CSR3 ${\times}$ CSR6 and their reciprocals (CSR4 ${\times}$ CSR2, CSR5 ${\times}$ CSR2 and CSR6 ${\times}$ CSR3) which exhibited significant heterosis and over dominance, for commercial exploitation was discussed.

• Journal of Sericultural and Entomological Science
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• v.4
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• pp.57-61
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• 1965

In the silkworm fed on ginseng, the body weight and the cocoon weight were not only heavier, but also the ratio of a cocoon layer to a cocoon weight was higher than those in the control. Especially, the heavier pupae were appeared. The ginseng may be therefor available in silkworm improvement.

• International Journal of Industrial Entomology and Biomaterials
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• v.7 no.1
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• pp.29-36
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• 2003

Phytoecdysteroids with moulting hormone (MH) activity induce different responses in silkworms when used on different day of final instar, which can be manipulated for maximum benefit like early and uniform spinning behaviour, reducing crop loss and to increase cocoon yield. The results showed that application of this hormone on seed crop viz., CSR2, CSR4 and BL44 and BL67 in early stage of 5$^{th}$ instar i.e., at 72 hrs and 96 hrs though induced early and uniform spinning behaviour, there was an adverse effect by 9-36% on the economic characters like cocoon yield, cocoon weight, cocoon shell weight and also on fecundity etc. Application of this hormone in late stage of $5^th$ instar i.e., at the onset of spinning showed non-significant variations in some of the characters like cocoon weight, cocoon shell weight, cocoon shell ratio and fecundity. The physiological implications of phytoecdysteroid in hastening the maturation events and synchronization of spinning activities in different breeds are discussed.

• Journal of Sericultural and Entomological Science
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• v.10
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• pp.77-80
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• 1969

The purpose of this study is to find out reasonable method for the estimation of silk yield in cocoon layer. Two season's cocoons were used as the materials, and three characters, cocoon weight (X$_1$), cocoon layer weight (X$_2$), and cocoon layer ratio (X$_3$) were studied. The formulae to estimate the silk yield of cocoon weight are as follows: 1. Estimation of silk yield in cocoon weight of the spring cocoons. 1). the case of cocoon weight 200 cg above; Y= 12.93＋0.0863X$_1$＋0.2135X$_2$＋2.1137X$_3$ 2). the case of cocoon weight 180～200 cg; Y= 18.59＋0.1354X$_1$＋0.0763X$_2$＋1.7397X$_3$ 3). the case of cocoon weight 160～180 cg; Y= 133.39-0.4400X$_1$＋2.6595X$_2$-3.4364X$_3$ 4). the case of cocoon weight 160 cg under; Y-71.74-0.213X$_1$＋1.3100X$_2$-0.0101X$_3$ 2. Estimation of silk yield in cocoon weight of the autumn cocoons. 1). the case of cocoon weight 180～200 cg; Y=214.07-0.8078X$_1$＋4.1664X$_2$-6.8229X$_3$ 2). the case of cocoon weight 160～180 cg; Y=40.16-0.0264X$_1$＋0.1896X$_2$＋1.9299X$_3$ 3). the case of cocoon weight 130～160 cg; Y= 86.64-0.3352X$_1$＋1.6104X$_2$-0.2110X$_3$ 4). the case of cocoon weight 130cg under; Y=207.76-1.4579X$_1$＋7.7811X$_2$-6.9496X$_3$

• Journal of Sericultural and Entomological Science
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• v.37 no.2
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• pp.114-120
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• 1995

The effect of juvenile hormone analogue(JHA, Manina) on larval feeding duration, pupation ratio, cocoon weight, and cocoon shell weight in the present commercial parent and hybrid silkworm stocks were investigated. Topical applications of JHA on parent silkworm stocks were to prolong larval duration, but results of response on those stocks were not consistent. Especially the JHA on Jam 121, Jam 123 and Jam 138 did not play a role in larval duration, whereas that on Jam 114 was most effective in prolongation more than two days, compared with the controls. subsequent prolongation of feeding duration resulted in increase of cocoon weight and cocoon shell weight of most parent silkworm stocks, while Jam 114 showed decrease in cocoon weight and cocoon shell weight in spite of prolonged feeding duration of two days. Unlike the parent silkworm stocks, durations of feeding period in all hybrid silkworm stocks were prolonged about one day. Treatments of JHA on the hybrid stocks gave rise to increase of cocoon weight and cocoon shell weight, and especially were most effective in Sasung-jam, Eunbaek-jam and Samgwang-jam. Although treatments of JHA seemed to have no harmful effect on physiology of parent silkworm stocks as well as that of hybrid stocks, the JHA retarded pupation ratio of some parent silkworm stocks such as Jam 122, 131, 135 and 138 by about 10%.