• 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.15-20
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• 2003

The present investigation was carried out to study the possible cause for reciprocal difference in silkworm hybrids. By utilising the polyvoltine race Pure Mysore (PM) and newly evolved breeds (CSR2, CSR5, CSR16 and CSR17), the direct and reciprocal crosses of polyvoltine ${\times}$ bivoltine and also bivoltine hybrids were studied. The hybrids of polyvoltine ${\times}$ bivoltine (direct) are superior to their reciprocal crosses in respect of cocoon yield, cocoon weight and filament length. The reciprocal crosses of polyvoltine ${\times}$ bivoltine are superior to their direct crosses in respect of fecundity and short larval duration. No significant differences were observed in the characters like cocoon shell ratio, raw silk percentage, denier, reelability and neatness in both polyvoltine ${\times}$ bivoltine direct crosses and their reciprocals. The expression of cocoon characters as a function of sex revealed that direct crosses (polyvoltine ${\times}$ bivoltine) showed higher cocoon weight, pupal weight, shell weight and longer filament length in females than the reciprocal crosses (bivoltine ${\times}$ polyvoltine), where as these characters in males were almost the same in both direct and reciprocal crosses, indicating that the sex-linked genetic factor played a more important role. it was clear that difference in cocoon yield observed in reciprocal crosses of polyvoltine ${\times}$ bivoltine was due to the low cocoon and shell weight in females which was turn due to presence of early maturity genes (Lme) linked with sex-chromosome (X) which effect on larvae period of the silkworm. In bivoltine hybrids, i.e., both direct and their reciprocals crosses, all the characters viz., hatching percentage, larval duration, survival, cocoon weight, cocoon shell weight, cocoon shell ratio, raw silk percentage, filament length, denier, reelability and neatness did not show any significant difference (except number of eggs laid by moth) which could account for presence of same maturity genes (Lm) in both direct and reciprocal crosses. it was clear that reciprocal differences occur when the hybrids are prepared from the parental strains with different voltinism.

• International Journal of Industrial Entomology and Biomaterials
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• v.13 no.2
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• pp.119-122
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• 2006

As the Selenium is known to be growth promoter in sheep and cattle, the efficacy of selenium has been tested in silkworm Bombyx mori L. The V instar larvae were fed with lethal and sub-lethal doses of selenium treated leaves. The larvae fed with lethal dose showed a significant decrease in growth and Cocoon commercial characters. The treatment with sub lethal dose exhibited a significant increase in the growth of the silkworm. Correspondingly, the cocoon commercial characters on exposure to the lethal dose showed significant decrease and sub lethal dose showed a significant increase. In the light of similar findings reported earlier in other cocoon crops and vertebrates, it can be inferred that selenium at lower doses acts as a growth stimulator, resulting in the higher yield of cocoon crop.

• 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 $NB_{4} D_{2}$.

• International Journal of Industrial Entomology and Biomaterials
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• v.11 no.1
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• pp.75-78
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• 2005

Inheritance of cocoon and shell weight characters in silkworm crosses between sex-limited at larva stage lines, including three (NIG$_{1}$ $\times$ TV$_{3/2}$ ,NIG$_{1}$ $\times$ TBV$_{2/24}$ and NIG$_{1}$ $\times$ B$_{2/6}$ ) from Japanese type and three (NIG$_{2}$ $\times$ B$_{2/6}$ ,TV$_{3/2}$ $\times$ NIG$_{1}$ and NIG$_{2}$ $\times$ TBV$_{2/24}$ ) from Chinese type was studied at Regional Centre for Scientific­Applied Service - Vratza during the period of 2000 ­2002. Inheritance of tested characters in F I was deter­mined through genetic parameters, additiveness (a), dominance (d) and their ratio (d/a). Degree and frequency of transgressions in F$_{2}$ were calculated also. Over dominance (d/a(>) 1) with bigger contribution of the parent with higher value was determined at inheritance tested characters. Transgressions obtained at cocoon and shell weight characters were positive and varied in wide limits. The productivity of parent's lines had defined the variability of genetic parameters for degree and frequency of transgressions. Combination of positive transgressions at cocoon and shell weight characters in F2 hybrid populations from sex-limited at larva stage allow us to select individuals with high productive potential for further use in selection programs.

• Journal of Sericultural and Entomological Science
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• v.29 no.2
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• pp.7-14
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• 1987

Extensive studies were undertaken to analyze the genetic basis of economically important quantitative characters in the silkworm by diallel crosses of four inbred lines differing widely in silk yielding ability. Some differences between the reciprocal corsses were detected in cocoon weight, cocoon shell weight, cocoon filament length and cocoon filament weight in case the parental lines were greatly differenent each other in silk yielding ability. The general combining ability (GCA) varied with the inbred lines and M242, a Chieese sexlimited larval marking variety showed high GCA value in the economic characters, such as cocoon yield, cocoon weight, cocoon filament length and weight, and raw silk percentage. The highest heterosis effect, about 13% to 14% was seen in cocoon and raw silk yield and it was low in cocoon reelability and raw silk percentage with less than 1%. It is advisable to improve highly heritable quantitative characters such as larval duration, cocoon shell weight, cocoon filament length and raw silk percentage by means of selection, and to select single crosses with high heterosis effect for cocoon weight and cocoon yield which show overdominance. Genetic correlation should be considered when more than two characters are targets for improvement and selecting high cocoon shell weight is effective to breed high silk yielding varieties. It is difficult to improve cocoon reelability because of low heritability (0.11) and its negative correlation with cocoon-silk quality.

• Journal of Sericultural and Entomological Science
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• v.27 no.1
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• pp.31-36
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• 1985

Using sexual differences between female and male as the indication of the degree of the physiological distrubance in the sex-limited larval marking strains or sex-limited egg colour strains, it was investigated whether the physiological distrubance caused y the translocated autosome fragment on the W-sex determination chromosome, have an effect on expression of the three quantitative characters; cocoon weight, cocoon shell weight, and cocoon shell percentage in the female silkworm. The mean values of the ratios of female to male the above two experimental groups were 127%, 107%, 85%, in cocoon shell weight, and cocoon shell percentage, respectively. On the other hand, those from the three normal stains, namely the basic stock strains, white egg strains, and hybrids were 129% for cocoon weight, 110% for cocoon shell weight, and 85% for cocoon shell percentage, respectively. From the results, it comes to the conclusion that the translocated autosome fragment on the W-chromosome has no influences on the expression of the quantitative characters of the female silkworm because sexual differences of the sex-limited strains were very similar to those of the three normal strains.

• 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.28 no.1
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• pp.24-29
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• 1986

A set of 21 crosses of F1 generation by diallel crosses from seven parent silkworm, Bombyx mori L. were used as materials to estimate genetic parameters such as gene action and combining ability. Experiments were conducted in 1985, and three characters, which are weight of cocoon, weight of cocoon layer and ration of cocoon layer, were observed. The data were analyzed for each character by Jinks', Hayman's and Griffing's methods. The result obtained are summarized as follows : 1. In Vr-Wr graphical analyses, weight of cocoon was found to be inherited in over dominance, and weight of cocoon layer and ration of cocoon layer were observed as partial dominance. 2. Estimate of additive component of variance(D) was greater than those of dominance component of variance(H) for weight of cocoon layer and ratio of cocoon layer, and positive values of F were observed for all characters. 3. Mean squares of general combining ability were higher than those of specific combining ability. 4. Variety Jam 107 was expressed as the highest GCA effects for three characters, and high SCA effects for all characters were observed in combinations of 113 $\times$Jung 14 and Jam 107 $\times$Jung 14.

• Journal of Sericultural and Entomological Science
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• v.34 no.1
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• pp.21-29
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• 1992

In the experiment, gene actions 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 analysis of variance, significantly maternal and reciprocal effects were observed for all character except female cocoon shell percentage and female pupal weight. Over-dominance was shown by Vr-Wr graphic analysis in three characters such as female cocoon weight, female and male pupal weight, and partial dominance in five characters such as male cocoon weight, cocoon shell percentage in both female and male. Component of genetic varience analyzed for five characters such as male cocoon weight, cocoon shell weight, cocoon shell percentage in both female and male showed that additive effects were higher than dominant effects, and female cocoon weight showed dominant effects higher than additive effects. Heritability of narrow sence was higher more than 0.51 and heritability of broad sence was higher more than 0.77 in all characters except for female pupal weight. The directions of dominance were negative for female cocoon shell weight and somewhat higher for female and male cocoon shell percentage. Meanwhile cocoon weight, pupal weight in both female and male showed positive in the direction of dominance.