• International Journal of Industrial Entomology and Biomaterials
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• v.15 no.1
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• pp.17-21
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• 2007

An indigenous multivoltine silkworm, Nistari was evaluated for their thermo tolerance by exposing the larvae to various temperature regimes for eight hours. Among different temperature exposed, this strain has significant tolerance at $32^{\circ}C$. Analysis of heat shock protein revealed the expression of 70 kDa and 64 kDa polypeptides in fat body and midgut tissues. Interestingly esterase isozyme pattern in midgut showed characteristic expression of Est-1 and Est-3 at different temperatures signifying role in heat and cold shock.

• 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.19 no.2
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• pp.243-248
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• 2009

The Larval critical weight is the minimal mass at which further growth in not necessary for a normal time course to pupation. Larval critical weight (Lcw), pupal critical weight (Pcw) and adult critical weight (Acw) of different breeds of Bombyx mori L. were determined through starvation (food deprivation). The Lcw was found to be about 938.46, 2397.26, 2283.57 and 2220.97 mg in males and 1118.15, 2681.04, 2604.9 and 2455.88 mg in females of the multivoltine breed (Nistari), Bivoltine breeds (P5 & NB18) and their hybrid (P5$\times$NB18) respectively. Bivoltine breed P5 took more time (3.35 days) followed by NB18 (3.13 days) & P5$\times$NB18 (3.02 days) to attain larval critical weight (In $5^{th}$ Instar) than the multivoltine breed Nistari (2.42 days). Decrease in weight from larval maximal weight to pupal weight and to adult weight was also observed more in multivoltine than bivoltines, which may be due to more latent feeding period in bivoltines. Since Lcw is a stable character and independent of environment, it could be utilized for characterization of silkworm breeds to assess the quality of an insect.

• International Journal of Industrial Entomology and Biomaterials
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• v.7 no.1
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• pp.21-27
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• 2003

Manifestation of heterotic genetic interaction was studied in different hybrids made between multivoltine recurrent backcross (RBL)/congenic lines (Con. L) during unfavourable season when temperature and relative humidity are > $30^{\circ}C$ and 86%, respectively. A few number of silkworm race or strain or breed like Nistari (N ＋ p or Np) can sustain the temperature above 3$0^{\circ}C$ and RH above 86%. The present heterosis study screened a hybrid i.e., CB$_{5}$Lm5RBL1M$_{6}$DPC-LmE$^1$RBL and its reciprocal provided heterobeltiotic effect on survival by number and pupation rate at a magnitude of 20% (p < 0.01) and yield by weight of 10% (p < 0.01). Beside all the hybrids expressed heterosis over check - Nistari (N ＋ p) with better quality silk. Therefore, aforesaid hybrid may be useful for utilization at commercial level during adverse seasons of West Bengal.gal.

• International Journal of Industrial Entomology and Biomaterials
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• v.26 no.2
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• pp.74-80
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• 2013

Three new Multi ${\times}$ Bi combinations M.Con.4 ${\times}$ (SK6 ${\times}$ SK7), M.Con.4 ${\times}$ NB4D2 and Nistari ${\times}$ (SK6 ${\times}$ SK7) were studied in five seasons i.e. during the period of $18^{th}$ June - $12^{th}$ July, $30^{th}$ August - $23^{rd}$ September, $3^{rd}$ November - $2^{nd}$ December, $29^{th}$ January- $2^{nd}$ March and $30^{th}$ March-$25^{th}$ April with one control Nistari ${\times}$ NB4D2 considering nine reeling characteristics along with shell percent and cocoon yield per 100 disease free layings (DFLs) to establish the seasonal effect on all the parameters. Results reveal that all the characters performed well in November-December. Highest yield per 100 DFLs was recorded during November-December in all combinations showing >60 kg yield. Higher correlation of yield/100 DFLs with filament length, non-breakable filament length, denier, raw silk percent, reelability percent and recovery percent was recorded in all combinations of Multi ${\times}$ Bi considered in this study. Variability observed among four combinations indicates the effect of different temperature and humidity of different seasons on expression of different traits. The results indicate that there is significant relationship of raw silk percent with reelability percent, recovery percent and evenness. Reelability percent showed higher correlation with recovery percent. It was observed that neatness was positively correlated with evenness. The overall performance of the newly evolved combinations with regard to productivity and reeling characteristics is discussed emphasizing their utilization at commercial level.

• International Journal of Industrial Entomology and Biomaterials
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• v.2 no.2
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• pp.107-110
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• 2001

Variations in protein and nucleic acid concentrations were observed in 24 hrs old eggs and hatched larvae of Nistari strain, Bombyx mori, exposed to starvation. Three starvation treatments of 24,48 and 60 hrs were given separately from 0 hr old fifth instar larvae. Biochemical variations were studied in the resultant hatched larvae of one time starved parent, while the eggs obtained from parents receiving starvation in two successive generations were considered for the study. In hatched larvae, protein levers in 24 hrs starvation groups remained significantly higher over control (never starved) while the same was found to be lower in 48 and 60 hrs starvation individuals. The RNA concentration remained significantly higher in all the treated lots. However, DNA content was not found to be significantly altered in hatched larvae after exposure to feeding stress. Protein, RNA and DNA concentration of 24 hrs old eggs produced by all the starved groups of Nistari, which had deceived two consecutive starvation during parental generations, showed higher concentrations of these biomolecules over control. Hence, starvation induced alterations in protein and nucleic acids in eggs and hatched Iarvae are indicative of a preparatory phase adopted by the insect to acclimatise itself and its progeny to stress situations.

• International Journal of Industrial Entomology and Biomaterials
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• v.16 no.1
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• pp.21-27
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• 2008

The expression of heat shock protein genes (Hsp 70, Hsp 40, Hsp 20.8 and Hsp 20.4) against thermal stress in silkworm Bombyx mori was performed through semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Upon exposure of silkworm to two temperature regimes ($38^{\circ}C$ and $42^{\circ}C$), significant change in the expression of Hsp gene was observed as compared to the control. Hsp 70 and Hsp 40 showed increased expression than the small heat shock protein genes Hsp 20.8 and Hsp 20.4. The Hsp 70 showed increased expression during the recovery period as compared to 1 hr thermal treatments ($38^{\circ}C$/1 hr and $42^{\circ}C$/1 hr). Whereas, Hsp 40, Hsp 20.8 and Hsp 20.4 genes showed higher expression level at initial stages that later gradually decrease during recovery period. Tissue specific expression of Hsp 70 showed variation in the level of expression amongst the tissues. The mid gut and fat body tissues showed higher expression than the cuticle and silk gland tissue. The Hsp 70, Hsp 40 gene expression was analyzed in thermotolerant (Nistari) and thermo susceptible silk worm strain (NB4D2) and results showed significant variation in their expression level. The Nistari showed higher expression of Hsp 70 and Hsp 40 genes than the NB4D2. These findings provide a better understanding of cellular protection mechanisms against environmental stress such as heat shock, as these Hsps are involved in an organism thermotolerance.

• International Journal of Industrial Entomology and Biomaterials
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• v.14 no.1
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• pp.1-7
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• 2007

In order to find out the appropriate parents for the breeding programme, twelve bivoltine and three multivoltine silkworm breeds were evaluated on the basis of multivariate selection index and isozyme analysis. Of which, four [CSR2, D6 (P), SK3, SK4] bivoltine and two multivoltine (Nistari, Cambodge) breeds were selected and breeding initiated to develop higher survival bivoltine silkworm breed suitable for tropical conditions. Among two isozyme (Esterase and acid phosphatase) analyzed, only esterase exhibited polymorphism among the bivoltine breeds. No polymorphism was observed among multivoltine in respect of esterase as well as acid phosphatase.

• Molecules and Cells
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• v.25 no.4
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• pp.467-478
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• 2008

Simple sequence repeats (SSRs) and interSSR (ISSR) marker systems were used in this study to reveal genetic changes induced by artificial selection for short/long larval duration in the tropical strain Nistari of the silkworm Bombyx mori. Artificial selection separated longer larval duration (LLD) ($29.428{\pm}0.723days$) and shorter larval duration (SLD) ($22.573{\pm}0.839days$) lines from a base, inbred population of Nistari (larval span of $23.143{\pm}0.35days$). SSR polymorphism was observed between the LLD and SLD lines at one microsatellite locus, Bmsat106 ($CA_7$) and at two loci of 1074 bp and 823 bp generated with the ISSR primer UBC873. Each of these loci was present only in the LLD line. The loci segregated in the third generation of selection and were fixed in opposite directions. In the $F_2$ generation of the $LLD{\times}SLD$ lines, the alleles of Bmsat106 and $UBC873_{1074bp}$ segregated in a 1:1 ratio and the loci were present only in the LLD individuals. $UBC873_{823bp}$ was homozygous. Single factor ANOVA showed a significant association between the segregating loci and longer larval duration. Together, the two alleles contributed to an 18% increase in larval duration. The nucleotide sequences of the $UBC873_{1074bp}$ and $UBC873_{823bp}$ loci had 67% A/T content and consisted of direct, reverse, complementary and palindromic repeats. The repeats appeared to be "nested" (59%) in larger repeats or as clustered elements adjacent to other repeats. Of 203 microsatellites identified, dinucleotides (67.8%) predominated and were rich in A/T and T/A motifs. The sequences of the $UBC873_{1074bp}$ and $UBC873_{823bp}$ loci showed similarity (E = 0.0) to contigs located in Scaffold 010774 and Scaffold 000139, respectively, of the B. mori genome. BLASTN analysis of the $UBC873_{1074bp}$ sequence showed significant homology of (nt.) 45-122 with upstream region of three exons from Bombyx. The complete sequence of this locus showed ~49% nucleotide conservation with transposon 412 of Drosophila melanogaster and the Ikirara insertions of Anopheles gambiae. The A + T richness and lack of coding potential of these small loci, and their absence in the SLD line, reflect the active process of genetic change associated with the switch to short larval duration as an adaptation to the tropics.

• 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.