• Journal of Sericultural and Entomological Science
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• v.40 no.1
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• pp.27-32
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• 1998

One indigenous polyvoltine strain (Nistari) and two bivoltine strains viz. P5 and NB18 along with one bivoltine hybrid (P5$\times$NB18) were subjected for studies on the differences on some physiologically important biomolecules like protein, nucleic acids and cholesterol. Ovarian protein and RNA content remained significantly high in the bivoltine races and their hybrid over multivoltine breed, while, DNA and cholesterol content remained significantly low in all the breeds and the hybrid as compared to Nistari strain. However, the ovarian weight was higher in both the bivoltine breeds and their hybrid than that of Nistari. Higher ovarian weight together with more protein and RNA concentrations reflect the preparatory phase for production of diapausing eggs by the bivoltine silknoths and their hybrid. The variations in biochemical parameters studied herein, thus establish a distinct difference in the overt reproductive physioiogy between multivoltine and bivoltine silkworms.

• International Journal of Industrial Entomology and Biomaterials
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• v.5 no.1
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• pp.59-65
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• 2002

Parthenogenetic development, hybrid vigour and cocoon shape variability were studied in bivoltine F1 hybrids of the silkworm, Bombyx mori L. Considerable breed differences were observed in parthenogenetic ability. Among the parental breeds, CSR18 exhibited maximum parthenogenetic development (79.65%) followed by CSR4 (67.90%). Among bivoltine F1 hybrids, CSR18 ${\times}$ CSR4 showed highest parthenogenetic development (73.32%) followed by CSR2 ${\times}$ CSR4 (55.43%). Study on hybrid vigour demonstrated that CSR18 ${\times}$ CSR19 expressed maximum significant hybrid vigour for all the seven economic characters over Mid Parent Value (MPV) followed by CSR2 ${\times}$ CSR4 and CSR18 ${\times}$ CSR4 exhibiting significant heterosis for six characters. Cocoon shape measurement study revealed that among ten bivoltine F1 hybrids, cocoons of three hybrids were found comparatively uniform. Importance of this study to know the level of paythenogenetic development, hybrid vigour and cocoon shape variability in different bivoltine F1 hybrids have been discussed.

• International Journal of Industrial Entomology and Biomaterials
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• v.6 no.2
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• pp.183-190
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• 2003

An attempt was made to identify superior bivoltine silkworm hybrid suitable for monsoon and spring season of Uttar Pradesh. Breeds with superior cocoon characters and their more popularity in an area were major parameters on basis of which breeds from different regions were selected. Six bivoltine hybrids of silkworm (Bombyx mori L.) of different geographical regions were reared in monsoon (three hybrids) and spring season (three hybrids) during 2000-2002 i.e., for three years at Babasaheb Bhimrao Ambedkar University, Lucknow. Their performances were analyzed statistically for nine characters. The analysis made on a number of traits viz., hatching percentage, larval duration, pupation rate, yield /10000 larvae (by no.), yield /10000 larvae (by weight), cocoon weight, cocoon shell weight, cocoon shell ratio, showed the superiority of one bivoltine hybrid out of the three bivoltine hybrids studied in each season. $SH6{\times}{NB_4}{D_2}$ was found to be superior in major cocoon parameters in both the seasons i.e., monsoon and spring season of Uttar Pradesh.

• International Journal of Industrial Entomology and Biomaterials
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• v.26 no.1
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• pp.22-30
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• 2013

The reproductive performance of multivoltine breed 'Nistari' and bivoltine breeds as NB18, P5 and a bivoltine hybrid (NB18 ${\times}$ P5) of B. mori were studied in different seasons in terms of total number of eggs laid, unlaid and hatching efficiency of the laid eggs to critically assess the breeds / hybrid potentiality. The bivoltine hybrid showed better performance in all the seasons as compared to the breeds investigated, as expected due to possibility of hybrid vigour. Among the breeds, bivoltine P5 had a better egg laid performance in S1 (February - March), S2 (May - June) and S3 (September - October) seasons but with an increase in the number of unlaid eggs. The hatching percentage, although didn't show any definitive trend, still suggested a marginal better performance in the hybrid. Most importantly, egg laying rhythmicity was studied by mating the female moth at 6.00 a.m. for $3{\frac{1}{2}}$ hours, and subsequently allowing the laying of eggs both under BOD condition ($25{\pm}1^{\circ}C$ and $85{\pm}5%$ RH) and at ambient temperature ($23-28^{\circ}C$ and $74.7{\pm}5%$) separately. Maximum (90%) egg laid occurred from 3.30 to 7.30 pm (i.e. 4 - 6 h after decoupling). Similar laying patterns were observed when females where mated at 12 noon and decoupled at 3.30 pm, revealing that late photoperiod and early scotoperiod were favourable for egg laying in case of multivoltine breed and bivoltine prefers late photoperiod for egg laying.

• International Journal of Industrial Entomology and Biomaterials
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• v.14 no.2
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• pp.93-97
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• 2007

A Silkworm breeding programme was designed to develop a robust but productive bivoltine silkworm hybrid of Bombyx mori L. suitable for rearing throughout the year in tropical climate by utilizing indigenous polyvoltine and productive bivoltine breeds. The breeding was carried out under high temperature ($36^{\circ}C{\pm}1^{\circ}C$) and low humidity ($50{\pm}5%$) conditions in the environmental chamber. By $F_{12}$, three oval and three dumbbell breeds were isolated with higher survival and productive merits. These breeds were utilized in the hybrid evaluation along with other popular breeds. Based on combining ability test results, the hybrid $SR_2{\times}SR_5$ was selected for large scale testing and evaluated in different seasons. The evaluation studies indicated that the hybrid has higher viability and productive merits and it is suitable to rear throughout the year. The hybrid $SR_2{\times}SR_5$ recorded a survival of 92.0%, cocoon shell weight of 0.417 g, cocoon shell percentage of 23.0 and a filament length of 1042 meters under hot and dry conditions of environmental chamber compared to the control thermo-tolerant hybrid $CSR18{\times}CSR19$.

• International Journal of Industrial Entomology and Biomaterials
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• v.4 no.1
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• pp.37-41
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• 2002

Heterosis studies on rearing performance of 25 Fl Polyvoltine $\times$ bivoltine (sex-limited cocoon colour) hybrids revealed that manifestation of heterosis was highly significant for majority of the economic traits contributing to more silk yield. Five hybrids namely BL24${\times}$ CSR 19 (SL), BL24${\times}$${\times}$${\times}$${\times}$${\times}$

• International Journal of Industrial Entomology and Biomaterials
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• v.5 no.1
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• pp.37-43
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• 2002

Eighteen new bivoltine silkworm (Bombyx mori L.) hybrids developed at Andhra Pradesh State Sericul-ture Research and Development Institute, Hindupur are evaluated for 10 economic traits by following two multiple trait index methods, i.e., Subordinate Function and Evaluation Index for their economic merit. The hybrid genotype, APS6${\times}$APS11 with highest Subordinate function value of 8.2432 and highest average Evaluation Index of 61.67 ranked first. This hybrid is adjudicated as most promising hybrid and recommended for commercial use. Further, applicability of Subordinate Function Index Method is tested and recommended for application of multiple trait evaluation similar to Evaluation Index Method as the results obtained are comparable. Further, both these methods can be applied for confirmation of results.

• International Journal of Industrial Entomology and Biomaterials
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• v.8 no.1
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• pp.43-49
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• 2004

Ten promising polyvoltine mulberry silkworm strains(SDMGl, SDMG2, SDMG3, SDMG4, SDMWl, SDMW2, RMWl, RMW2, RMW3 and RMW4) that are superior in quantitative and qualitative traits have been synthesized in the polyvoltine breeding laboratory of Andhra Pradesh State Sericulture Research ＆ Development Institute, Hindupur through systematic hybridization and appropriate selection methods. After the genotypes were found homozygous for the desired traits, they have been crossed with 3 bivoltine testers $(APS8, APS4 and {NB_2}{D_4})$ and thirty new hybrid combinations were developed for the assessment of their hybrid performance. Phenotypic expressions of economically important quantitative and qualitative traits of fist filial generation were measured and subjected for statistical analysis. Evaluation Index and Subordinate Function methods were employed for the assessment of hybrid performance since they are widely used in silkworm hybrid evaluation. Total of seven poly${\times}$bivoltine combinations, which ranked high in both the methods, were selected as potential combinations for further field test. These combinations also ranked significantly higher than the control hybrid (APMl${\times}$APS8).

• International Journal of Industrial Entomology and Biomaterials
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• v.13 no.2
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• pp.63-72
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• 2006

Parthenogenesis, the development of unfertilized ovum opens new perspectives in silkworm breeding in the development of homozygous breeds. In order to improve induction of artificial parthenogenesis in the excised unfertilized eggs of different breeds of the silkworm, Bombyx mori L., a new method was devised and the results were compared with the routine method. General and specific combining abilities and hybrid vigour of newly developed bivoltine breeds were analyzed utilizing bivoltine breeds viz., $CSR_2,\;CSR_4,\;CSR_{17}\;and\;NB_4D_2$ Estimation of GCA revealed superiority of the breeds, $DNB_1$ for eight characters followed by $DNB_4$ for five characters. Among the testers, $CSR_2$ was found good general combiner for seven characters followed by $CSR_{17}$ for four characters. A great deal of variations was observed among the hybrids studied. Five hybrids namely, $DNB_1{\times}CSR_2,\;DNB_4{\times}CSR_4,\;DNB_4{\times}NB_4D_2,\;DNB_6{\times}CSR_2\;and\;DNB_7{\times}CSR_2$ showed significant SCA effects for 5-6 characters. The hybrid, $DNB_4{\times}CSR_4$ showed its superiority by expressing significant hybrid vigour over BPV for 7 characters. Majority of the hybrids exhibited significant hybrid vigour for survival rate, yield/10,000 larvae by weight, cocoon weight, cocoon shell weight, filament length and denier.

• 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.