• International Journal of Industrial Entomology and Biomaterials
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• v.9 no.1
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• pp.1-13
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• 2004

Indian multivoltine mulberry silkworm (Bombyx mori L.) strains are poor in silk productivity and fibre quality. However, they are commercially exploited for the past five decades either in the form of pure breeds or cross breeds because of their adaptability to adverse climatic condition and acclimatization to specific regions and seasons. In the present paper conservation strategies of multivoltine silkworm genetic resources are dealt along with detailed information on accessibility of genetic resources, method of genetic resources conservation, characterization of genetic resources for morphological and productivity traits of economic importance. Selection of best ten accessions based on various economic parameters including yarn quality and their scope for future utilization are discussed.

• International Journal of Industrial Entomology and Biomaterials
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• v.15 no.1
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• pp.1-7
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• 2007

At present, multivoltine silkworm races reared five times per year involving huge manpower and rearing expenditure. Egg diapausing behavior is facultative in multivoltine and egg diapause was induced in selected multivoltine races by regulating temperature at $18^{\circ}C$, relative humidity 80% and photoperiod (6L:18D) in the late stage silkworm rearing. The maximum percentage of egg diapause induction was recorded in Rong Diazo, Diazo and MW13 showed 94%, 93% and 92% respectively, whereas the races A14DY and OS-616 showed minimum diapause induction 15% and 18% respectively. The diapause induced multivoltine eggs were preserved up to six months by cold preservation schedule normally adopted for bivoltine. After three and six months egg preservation, the diapause induced layings were released and observed for hatching percentage, all races showed above 82 % of hatching except the race AP12, which showed only 78 % of hatching. This methods reduce the crop cycle, gives strong safety backup and preventing the genetic erosion. This study helps formulating a new conservation method for multivoltine silkworm germplasm.

• International Journal of Industrial Entomology and Biomaterials
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• v.11 no.2
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• pp.93-98
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• 2005

Studies on extended egg preservation schedule from 120 days to 180 days was taken up with 20 germplasm accessions of mutant silkworm genetic stocks of Bombyx mori L. Statistical analyses of the data collected over three trials revealed no significant changes both in the qualitative and quantitative traits of the genetic stocks between treatment (6 months egg preservation) and control (4 months egg preservation), except for fifth instar larval duration in TMS-61, TMS-62, TMS64, TMS-31 and TMS-34 shell weight in TMS-62, TMS-64 and TMS-66. Thus, the results indicate that extended schedule of 6 months egg preservation can safely be adopted, which will reduce the cost of conservation and minimize the genetic erosion owing to reduced crop cycle.

• International Journal of Industrial Entomology and Biomaterials
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• v.9 no.1
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• pp.79-87
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• 2004

The silkworm rearing and growth parameters of 63 multivoltine silkworm accessions under extended period of egg preservation at 5$^{\circ}C$ from 30 days to 45 days were studied. The results indicate that, nine accessions did not respond to extended period of egg preservation at low temperature and the remaining 54 accessions responded to the treatment and three rearings were conducted for comparision with the control; to estimate the effect of prolonged egg preservation at low temperature. The non-parametric tests statistics (Wilcoxon tests) was adopted for comparing the mean performance of treated batches (45 days) over the control (30 days). Highly significant variability was found among the accessions for all the parameters under study. The genetically controlled morphological characters were not altered in the treated batches, which were found to be on par with that of control. However, the total larval duration varied significantly over the control in 51 accessions. Similarly, the fifth age larval duration of 27 accessions showed decreasing trend compared to control. Altogether 41 accessions were found to be tolerant to long-term cold preservation upto 45 days, without showing any significant variation for morphological as well as essential quantitative traits. These accessions may be recommended for long-term egg preservation schedule up to 45 days, which will reduce the cost of conservation of these silkworm germplasm.

• International Journal of Industrial Entomology and Biomaterials
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• v.13 no.2
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• pp.113-117
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• 2006

Heterosis was studied involving two multivoltine silkworm breeds viz, APM1 and SLKSPM through rearing and isozyme analysis. A positive significant heterotic effect was observed in fecundity, hatching % and survivability. The heterobeltiosis was observed only in fecundity and hatching %. Isozyme analysis of ${\alpha}-esterase$ showed variation in loci and allelic expression. The allele with heterozygosity $(Est-2^{12})$ was observed at the Est-2 locus in $F_1$ progeny. Est-3 was observed in $F_1$ progeny, whereas it was completely absent in both parental lines. The present study suggests that the markers ($Est-2^{12}$ and Est-3) targeted for introgression may be useful for the improvement of fecundity and survivability as the phenomenon of heterosis was observed only in $F_1$ progeny.

• International Journal of Industrial Entomology and Biomaterials
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• v.14 no.1
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• pp.23-32
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• 2007

The nature of genetic variation and diversity among the 65 multivoltine silkworm genotypes was evaluated for 16 post cocoon characters. The components of genetic variation revealed higher PCV (60.487%) and GCV (44.56%) for evenness (variation 1) followed by cohesion (PCV=55.38%, GCV=40.36%) and non-broken filament length (PCV=32.05%, GCV=31.28%). The higher heritability ($h^2$ in broad sense) was observed for boil-off loss (95.6%) followed by non-broken filament length (95.22%). The both genotypic and phenotypic correlation indicated significant positive correlation of filament length with non-broken filament length, silk recovery, raw silk, neatness, and low neatness; and negative correlation with denier, renditta and silk waste. The principal component analysis (PCA) revealed 75.381 % of total variance from the five principal components extracted. On the basis of Mahalonobis' $D^2$ values (Ward's minimum variance), the sixty-five multivoltine silkworm genotypes were classified in to 9 clusters with substantial inter and intra cluster distances. Number of genotypes included in different clusters varied from 3 to 17. The results indicated that the optimum distance obtained in cluster VII (15.059) along with higher cluster mean values especially for filament length, non broken filament length, renditta, silk recovery, silk waste, and raw silk emphasized the utilization of these genotypes in the conventional silkworm breeding programme for improvement of multivoltine silk fibre quality. The possibility of exploiting genetic variation in post cocoon traits for efficient breeding programme is discussed.

• International Journal of Industrial Entomology and Biomaterials
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• v.7 no.1
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• pp.87-91
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• 2003

BmNPV (Bombyx mori nuclear polyhedrosis virus) causes nuclear polyhedrosis in silkworms. The tolerance of silkworms to BmNPV is controlled by polygenes. This paper reports on the relative tolerance of silkworm breeds among the germplasm maintained at Andhra Pradesh State Sericultural Research ＆ Development Institute (APSSRDI), Hindupur, India. The silkworm larvae out of second moult were per orally inoculated with BmNPV polyhedra $(l{\times}l0^{th}//ml)$ and reared upto spinning. The response to BmNPV had been categorized into apparent tolerance, real tolerance and susceptibility. Among the 145 silkworm breeds screened, 18 bivoltines and 16 polyvoltines were found to have real tolerance to BmNPV.

• International Journal of Industrial Entomology and Biomaterials
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• v.16 no.2
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• pp.37-48
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• 2008

The diapause and non diapause associated proteins of multivoltine silkworm eggs were analysed by two dimensional (2D) gel electrophoresis. The study was made at 0 hr, 24 hrs and 48 hrs after oviposition. A total of four protein spots in diapause eggs at 24 hrs of oviposition and two protein spots in non diapause eggs at 0 hrs of oviposition were observed. All the six protein spots were considered to have association with diapause and non diapause characters. The molecular weight (MW) and isoelectric point (PI) of these 6 protein spots were calculated. The protein spots 1 and 2 observed in 0 hr of non diapause eggs were found to have the MW of 67 and 75 KDa and PI of 8.6 and 8.4 respectively. Similarly the four protein spots observed in diapause egg at 24 hrs of oviposition exhibited MW viz., 15, 17,20 and 25 KDa and PI of 5.3, 5.8, 6.5 and 6.0 respectively. All these 6 identified protein spots were subjected to in-gel digestion and resulted tryptic peptides were analyzed by Matrix-assisted laser desorption/ionization time-of flight mass spectrometry (MALDI TOF-MS). Databases searched based on experimentally determined molecular weights of peptides for the determination of the identities of proteins. The identified proteins indicated homology of 34% to 95%. The results indicate that the proteins may playa role in development of diapause and non diapause eggs.

• International Journal of Industrial Entomology and Biomaterials
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• v.7 no.2
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• pp.221-229
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• 2003

Ten multivoltine female parental lines were crossed with popular bivoltine male silkworm breed NB$_4$D$_2$. Three types of heterosis parameters viz., heterosis over mid-parental value (hybrid vigour), heterobeltiosis (useful heterosis) and standard heterosis (standard check) were estimated for 15 economically important quantitative traits. The interaction among the hybrids and parents indicated significant effect for maximum characters. The heterotic effect of new hybrid combination was compared with popular hybrids viz., Pure Mysore${\times}$NB$_4$D$_2$ and Nistari${\times}$NB$_4$D$_2$. Varied heterotic effect was observed for different traits for different hybrid combination. The results inferred that the crosses viz., BL$_{23}$${\times}$NB$_4$D$_2$ ranked top for 14 traits followed by Hosa Mysore${\times}$NB$_4$D$_2$ for 11 traits; PA$_{12}$${\times}$NB$_4$D$_2$ for 9 traits; BL$_{24}$${\times}$NB$_4$D$_2$ for 8 traits; Kolar Gold${\times}$NB$_4$D$_2$ for 7 traits; WAI$_1$${\times}$NB$_4$D$_2$ for 6 traits and MU$_{11}$${\times}$NB$_4$D$_2$ for 5 traits. Among these, the best hybrids Kolar Gold${\times}$NB$_4$D$_2$ and MU$_{11}$${\times}$NB$_4$D$_2$ were identified for longer filament length and fine denier. Similarly for higher cocoon yield and silk productivity BL$_{223}$${\times}$NB$_4$D$_2$ and BL$_{24}$${\times}$NB$_4$D$_2$ were found to be superior. These hybrid combinations are suitable for commercial exploitation at large scale.e.e.e.

• International Journal of Industrial Entomology and Biomaterials
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• v.15 no.2
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• pp.123-130
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• 2007

The Hsp 20.8 and Hsp 90 cDNA sequence retrieved from NCBI database and consists of 764 bp and 2582 bp lengths respectively. The corresponding cDNA homologus sequences were BLAST searched in Bombyx mori genomic DNA database and two genomic contigs viz., BAAB01120347 and AADK01011786 showed maximum homology. In B. mori Hsp 20.8 and Hsp 90 is encoded by single gene without intron. Specific primers were used to amplify the Hsp 20.8 gene and Hsp 90 variable region from genomic DNA by using the PCR. Obtained products were 216 bp in Hsp 20.8 and 437 bp in Hsp 90. There was no variation found in the six silkworm races PCR products size of contrasting response to thermal tolerance. The comparison of the sequenced nucleotide variations through multiple sequence alignment analysis of Hsp 90 variable region products of three races not showed any differences respect to their thermotolerance and formed the clusters among the voltinism. The comparison of aminoacid sequences of B. mori Hsps with dipteran and other insect taxa revealed high percentage of identity growing with phylogenetic relatedness of species. The conserved domains of B. mori Hsps predicted, in which the Hsp 20.8 possesses ${\alpha}-crystallin$ domain and Hsp 90 holds HATPase and Hsp 90 domains.