Silk Yield Research Articles

Phosphoproteomic analysis of the posterior silk gland of Bombyx mori provides novel insight into phosphorylation regulating the silk production

To understand phosphorylation event regulating silk synthesis in the posterior silk gland of Bombyx mori, phosphoproteome was profiled in a pair of near-isogenic lines, a normally cocooning strain (IC) and a nakedly pupated strain (IN) that the silk production is much lower than IC. In the posterior silk gland of the IC and IN, 714 and 658 phosphosites resided on 554 and 507 phosphopeptides from 431 and 383 phosphoproteins, were identified, respectively. Of all the phosphosites, the single phosphosite was the dominate phosphorylation form, comprising>60% of all the phosphosites in two phenotypic of silk production. All these phosphosites were classified as acidophilic and proline-directed kinase classes, and three motifs were uniquely identified in the IC. The motif S-P-P might be important for regulating phosphorylation network of silk protein synthesis. The dynamically phosphorylated proteins participated in ribosome, protein transport and energy metabolism suggest that phosphorylation may play key roles in regulating silk protein synthesis and secretion. Furthermore, fibroin heavy chain, an important component of silk protein, was specifically phosphorylated in the IC strain, suggesting its role to ensure the normal formation of silk structure and silk secretion. The data gain new understanding of the regulatory processes of silk protein synthesis and offer as starting point for further research on the silk production at phosphoproteome level. Significance of this studyDespite the knowledge on regulation of silk protein synthesis in the posterior silk gland has gained at the gene or protein levels, how phosphorylation event influences the silk yield is largely unknown. To this end, we constructed a pair of silkworm near-isogenic lines that showed different cocooning phenotypes, and the phosphoproteome of the posterior silk gland of two isolines was compared. Here, we reported the first phosphoproteome data on the silkworm and found several key pathways related protein synthesis are regulated by phosphorylation, thereby influencing the silk production. The data provide valuable resources for further functional assay of targeted protein phosphorylation that regulates the silk synthesis in silkworm.

Genome-wide Identification and Structural, Functional and Evolutionary Analysis of WRKY Components of Mulberry

Mulberry is known to be sensitive to several biotic and abiotic stresses, which in turn have a direct impact on the yield of silk, because it is the sole food source for the silk worm. WRKYs are a family of transcription factors, which play an important role in combating various biotic and abiotic stresses. In this study, we identified 54 genes with conserved WRKY motifs in the Morus notabilis genome. Motif searches coupled with a phylogenetic analysis revealed seven sub-groups as well as the absence of members of Group Ib in mulberry. Analyses of the 2K upstream region in addition to a gene ontology terms enrichment analysis revealed putative functions of mulberry WRKYs under biotic and abiotic stresses. An RNA-seq-based analysis showed that several of the identified WRKYs have shown preferential expression in the leaf, bark, root, male flower, and winter bud of M. notabilis. Finally, expression analysis by qPCR under different stress and hormone treatments revealed genotype-specific responses. Taken together, our results briefs about the genome-wide identification of WRKYs as well as their differential response to stresses and hormones. Importantly, these data can also be utilized to identify potential molecular targets for conferring tolerance to various stresses in mulberry.

Expression of Heterosis in Bivoltine Hybrids of Bombyx mori L. for Silk Yield Contributing Traits under Sub-tropical Conditions

Expression of Heterosis in Bivoltine Hybrids of Bombyx mori L. for Silk Yield Contributing Traits under Sub-tropical Conditions

Evaluations of Different Montage Types and Sizes on Eri and Mulberry Feeding Silkworms Cocoon Yield and Quality of Silk, at Melkassa Agricultural Research Center, East Shoa, Ethiopia

The experiments were conducted at Melkassa Agricultural Research Center in the sericulture and apiculture research laboratory during 2011 mountage types (ply wood, cartoon made, Banana leaf, plastic board, rolling paper and mango leaf montages) and sizes (3x3cm, 3 x 4cm, 3 x 5 cm, 4 x4 cm, 4 x5 cm and 5 x5cm) were evaluated on Eri and Mulberry silkworm cocoon yield and quality of silk. In the mountage type evaluation, 4cm x4cm recommended mpuntage size was prepared from ply wood, cartoon and plastic board. Different mountage sizes were prepared from plywood purchased from th market. Hundred silkworm larvae’s were used for each mountage type and sizes, and the treatments were arranged in randomized block d humidity and temperatures of the laboratory were taken during the experiment percentage, defective cocoon percentage, reeling/spinning quality, average filament length and silk ratios were used to evaluate the montage types. Similarly, number of double pupae formation per cocoon, average weight of 10 cocoons five days a cocoon percentage, spinning /reeling quality, length of single cocoon and silk ratios were used to evaluate montage sizes. Significantly (P<0.01) higher cocooning percentage, lower defective cocoon percentage, higher spinning quality, higher filament length and silk ratios were recorded in plywood made, carton made and banana leaf made mountage than the other treatments followed by mango leaf made mountage for both Eri and mulberry silkworms. Number of double pupae formation per cocoon significantly lower in all sizes of the mountages except 5 cm x 5 cm mountage size for Eri silkworms. However, number of double pupae formation per cocoon significantly P<0.01 higher in 5cm x 5cm followed by 3cm x 5cm, 4cm x5cm mountage sizes than the other treatments for Mulberry silkworms. From this studies it can conclude that, plywood made, carton made and banana leaf made mountage followed by mango leaf mountage types should be recommended for eri and mulberry silk worms. It can also conclude that, 4cm x 4cm and 4cm x 5cm mountage size made from ply wood should be recommended for mulberry and Erisilkworms, respectively, and used by the end users. Copyright@2015 STAR Journal

Analyses of the Molecular Mechanisms Associated with Silk Production in Silkworm by iTRAQ-Based Proteomics and RNA-Sequencing-Based Transcriptomics.

Silkworm is used as a model organism to analyze two standard complex traits, which are high and low silk yields. To understand the molecular mechanisms of silk production, the posterior silk glands aged to the third day of the fifth instar were analyzed from the ZB strain with low silk production and from the control strain Lan10. Using isobaric tags for relative and absolute quantification (iTRAQ) quantitative shotgun proteomics and RNA-sequencing-based transcriptomics, 139 proteins and 630 transcripts were identified as novel in the ZB strain compared with the Lan10 strain, indicating that these results significantly expand the coverage of proteins and transcripts of the posterior silk glands in the silkworm. Of the 89 differently changed proteins, 23 were increased, and 66 were decreased. Of the 788 transcripts, 779 were upregulated, and 9 were downregulated. These results confirm that decreased energy utilization/protein translation and enhanced protein degradation are the key factors in lower silk production. Moreover, this study provides novel insight into the molecular changes that may result in lower silk production, namely, a combination of impaired transcription activity, missed protein folding/transport, and lowered yields of the main components of fibroin, along with weakened growth/development of the posterior silk gland.

Impact of Novel Bio-Foliar on Natural Cocoons and Silk Quality

Present study was carried out to improve the cocoon and silk quality by nursing with bio-foliar. Five mulberry varieties, namely, S-1, S-146, S-1635, AR-14, and BR-2 were fed to silkworms and cocoons produced by them were used for analysis. Results of the investigation indicated that highest cocoon weight (1.733 g), shell weight (0.349 g), shell ratio (20.144%), effective rate of rearing (97.50), silk filament length (1094.07 m), filament weight (0.315 g), denier (3.071 g/d), renditta (5.505 kg), non-breakable filament length (875.254 m), and silk yield (18.169%) were obtained by enriching BR-2 and S-1635 varieties with 45 ppm of bio-foliar compare to control.

Quantitative Profile Analysis of Mulberry Silkworm &lt;i&gt;Bombyx mori &lt;/i&gt;L. (CSR&lt;sub&gt;2&lt;/sub&gt;XCSR&lt;sub&gt;4&lt;/sub&gt;)

Bombyx mori. L. (CSR2XCSR4) is a bivolitne crossbreed that produces high quantity of silk. The weights of worms and glands are directly related to the yield of silk, higher larval weights leads to higher silk production. In the present study, quantitative parameters of 5th instar and pupal stages of silkworm larvae were observed. The analysis of quantitative estimation showed that the maximum weights and lengths of silk gland and silk worm were recorded on 7th day of 5th instar larval stage. The day dependent variation in protein concentration was observed in total silk gland 5th instar larval and pupal stages.

Quantitative Profile Analysis of Mulberry Silkworm &lt;i&gt;Bombyx mori &lt;/i&gt;L. (CSR&lt;sub&gt;2&lt;/sub&gt;XCSR&lt;sub&gt;4&lt;/sub&gt;)

Bombyx mori. L. (CSR2XCSR4) is a bivolitne crossbreed that produces high quantity of silk. The weights of worms and glands are directly related to the yield of silk, higher larval weights leads to higher silk production. In the present study, quantitative parameters of 5th instar and pupal stages of silkworm larvae were observed. The analysis of quantitative estimation showed that the maximum weights and lengths of silk gland and silk worm were recorded on 7th day of 5th instar larval stage. The day dependent variation in protein concentration was observed in total silk gland 5th instar larval and pupal stages.

Peril on the Silk Road

[stag_intro]Feeding frenzies, boiled alive, a royally guarded secret… The very dark and dangerous story behind one of the most romantic fabrics[/stag_intro] Valentine’s day is on the horizon, and silk lingerie is being scouted out by women as the choice attire for the romantic evening ahead and by men as the most sensual gift for their beloveds. But as the stores are awash in silk, who has given a thought to just who or what is behind the making of this most exquisite and sensual of all fabrics? And what exactly is being done to assure that silk production is protected for all Valentine’s days ahead? Silk production has a colourful history that is virtually unknown to most people. In fact, for more than two thousand years the Chinese kept the production of silk, or sericulture, a secret, the punishment for revealing the industry’s secrets or smuggling the silkworm eggs or cocoons outside of China being death. The fabric was for a long time reserved exclusively for royalty. Since they discovered it in 2700 BC, the Chinese have perfected the art of rearing silkworms for the production of silk from the filaments of the silkworm’s cocoon, and now sericulture has become one of the most important cottage industries in numerous countries, with China and India being its two main producers, followed by Brazil, France, Italy, Japan, Korea and Russia. Be warned, though, that unlike cotton, which is fairly easily extracted from the fibres of cotton shrubs, themselves quite hardy and found around the world, silk production is a bit more of a complicated and even deadly affair… To start, the silk industry favours one particular silk moth for use, the desperately hopeless Bombyx mori. Blind and flightless, this moth is only really good for making silk, and that it does extremely well, producing a filament that is smoother, finer and rounder than that of other moths. Highly fertile, each silk moth lays thousands of eggs, which hatch larvae, the silkworms, emerging to feed on fresh mulberry leaves until they are very fat. In fact, they multiply their weight 10,000 times within one month in what can only be described as a salad feeding frenzy to put a shiver of ravenous sharks to shame. At the same time, the worms are moulting, or shedding their skin, the silkworm having developed a veritable free body contouring surgery to coincide with its rapid weight increase. After shedding its skin four times, the silkworm weaves itself a cocoon, distributing a dense fluid secreted from its structural glands. Wildly propagating, gorging, shedding and spitting… exactly who is calling this romance? Having done so very little to endear itself while alive, it is now while blissfully cocooned, the silkworm larvae meet their untimely demise. One might be comforted that at least they don’t see it coming. The silk producer steams or bakes the cocoons in order to kill the worms inside, the cocoons are then dipped into hot water to loosen the filaments, and these are then unwound onto a spool. If this process does not sound challenging enough, Bombyx mori are a delicate, highly sensitive silkworm completely intolerant of fluctuating weather conditions, loud noises and strong smells. Really, the silkworm is the most finicky and intolerant of the luxe fashion trade, the insect world’s version of Anna Wintour. Is there a hope at all for the silk industry? Thankfully, yes. Because for all the environmental climatic conditions, where mother nature can wreak devastating havoc and technology can miserably fail, there is one answer to sericulture’s precarious market needs: index-based weather insurance. It may sound equally as unromantic as the silkworm itself, but it is just as fecund. China and India in particular may naturally enjoy the tropical conditions so beloved by silkworm, but take that temperature below 20 or above 30 degrees Celsius and the pernickety silkworm becomes too weak and susceptible to disease to be of much use at all. While such values may not mark good business for the silkworm, the sericulturalist may relax knowing that the adverse weather has triggered a payout anyway, as index-based weather insurance allows for contracts to settle based on values determined by the client, whether those are number of days a determined temperature has been reached, a threshold on the humidity index has been crossed, or any weather value determined by the farmer. There is no need to examine the ultimate yield of silk to determine damages as payment is automatic, without a field loss assessment. It may not be of much relief to the ill-fated Bombyx mori, but for silk producers and really any industry susceptible to the whims of mother nature, this Valentine’s Day, romance really is alive and well.

Evaluation of Macro and Micro Nutritive Elemental Levels in the Mealy-Bug (Maconellicoccus Hirsutus)- Infested Leaves of Mulberry (Morus Sp.)

The quality of mulberry leaf supports good growth and development of silkworm larvae. Mulberry leaves are hampered by the various detrimental diseases and pests. The mealy bug is one of the important insect pests of mulberry; its sap sucking nature may alter nutritive levels. An attempt was made to evaluate the macro and micro nutritive elemental levels in the infested leaves. There was a large variation of nitrogen, phosphorus, potassium, magnesium, manganese and molybdenum in almost all the varieties. There was a small difference in calcium, sulphur, iron, copper, boron and chloride. However, there was no change in zinc content in all the varieties of infested leaves. Disparity shown in majority of the macro nutrients in almost all the mulberry cultivars leads to variation in their quality. This feature of the leaves may hinder the good growth and development of silkworm, in turns producing low quality and poor yield of silk.

Impact of different silkworm dietary supplements on its silk performance

This study aims to evaluate the effect of silkworm larva (Bombyx mori) diet supplementation with two amino acids (threonine and valine) on the cocoon production and on the structural and mechanical properties of the silk produced. Negligible morphological differences were observed in the silk fiber threads from silkworm larvae supplemented with the tested amino acids. Higher production (yield) of silk was obtained using threonine in the diet of the silkworm. The treatments with threonine have increased the limit of proportionality, tensile strength, toughness, and maximum deformation of the thread of silk fibers. No significant increment in these properties was observed due to the increase in the threonine content. The treatments with valine led to lower increase in tensile strength and toughness. The real density of the silk has decreased with the use of supplements. The present study contributes to engineering of advanced silk materials, which should be attractive candidates for multipurpose applications.

Transcriptomic analysis of differentially expressed genes in the Ras1CA-overexpressed and wildtype posterior silk glands

BackgroundUsing the piggyBac-mediated GAL4/UAS transgenic system established in the silkworm, Bombyx mori, we have previously reported that overexpression of the Ras1CA oncogene specifically in the posterior silk gland (PSG) improved cell growth, fibroin synthesis, and thus silk yield. However, the detailed molecular mechanism remains to be fully elucidated. To achieve this goal, Illumina sequencing was used in the present study to compare the transcriptomes of the Ras1CA-overexpressed and wildtype PSGs.ResultsThe transcriptomic sequencing results in 56 million reads following filtering steps. Most of the reads (~70%) are successfully mapped to the Bombyx genome. The mapped reads are situated within at least 9,133 predicted genes, covering 62.46% genes of the Bombyx genome. GO annotation shows that 2512 of the 2,636 differentially expressed genes (DEGs) are mostly distributed in metabolic process, cell and cell part, and binding, and KEGG annotation shows that 1,941 DEGs are mapped into 277 pathways. Importantly, Ras1CA overexpression in the PSG upregulated many DEGs distributed in “pathways in cancer”, “insulin signaling pathway”, and “MAPK signaling pathway” as well as “purine metabolism” and “pyrimidine metabolism”. Transcriptional regulation of these DEGs was verified by quantitative real-time PCR. Moreover, injection of small-molecule chemical inhibitors of the Ras1 downstream effectors into the Ras1CA-overexpressed silkworms revealed that both Raf-MAPK and PI3K-TORC1 pathways are required for the Ras1-induced DEG expression.ConclusionThe transcriptomic analysis illustrates that, apart from phosphorylational regulation, Ras1 activates its downstream Raf-MAPK and PI3K-TORC1 pathways at the transcriptional level. Meanwhile, Ras1 increases DNA content and induces endoreplication, at least in part, by upregulating genes in “nucleotide metabolism” and “cell cycle”. This study provides further insights into the molecular mechanism of how Ras1CA overexpression in the PSG improves silk yield.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-182) contains supplementary material, which is available to authorized users.

Post infestation changes in the nutritive elements of thrips (Pseudodendrothrips mori) attacked mulberry (morus sp.) Foliage

Mulberry, the sole food of silkworm, Bombyx mori L. is prone to various pests and diseases. The injury caused during the feeding behavior of insect pests may alter the physiological activities and leading to imbalances in the nutritive constituents of the host plants. An study has been made to know the level of six macro (nitrogen, phosphorus, potassium, calcium, magnesium and sulphur) and seven micro nutrients (zinc, iron, manganese, copper, boron, molybdenum and chloride) elements in the thrips ( Pseudodendrothrips mori Niwa.) attacked leaves of six popularly cultivated mulberry varieties. The results revealed a large variation in the nitrogen, phosphorous, potassium, magnesium, sulphur and molybdenum content. The remaining elements were changed non-significantly. Feeding such leaves may cause a variation in growth and development of the silkworm, which results the low yield and poor quality of silk.

Biochemical Performance and Quantitative Assessment of F1 Hybrid of Two Ecoraces of Tropical Tasar Silkworm Antheraea Mylitta Drury (Lepidoptera: Saturniidae)

Antheraea mylitta Drury is basically a crossbreeding species, as such it seems to be potentially a good material for the exploitation of heterosis. In the present study F1 hybrid of wild ecorace Laria (L) and semi-domestic Daba (D) was raised and evaluated for various quantitative traits and biochemical parameters during larval stage. Improved fecundity (<TEX>$+18{\pm}1.8%$</TEX> and higher egg hatching rate (<TEX>$+10.96{\pm}1.3%$</TEX>) was recorded in the F1hybrid (<TEX>$L{\times}D$</TEX>). Biochemical parameters studied in the hemolymph, midgut and fatbody of the larva showed significantly higher (P<0.05) total proteins and carbohydrate concentration besides digestive enzyme activity. Correspondingly SDS-PAGE revealed more number of protein bands in the hemolymph sample of F1s, ranging between 29 kDa to 66 kDa compared to parental lines. The present study demonstrates the positive heterosis effect in the F1 hybrid of Laria <TEX>${\times}$</TEX> Daba. Biochemical analysis indicates that, there is possibilities of exploitation of hybrids with specific parents targeted for desirable commercial traits (silk yield and fecundity). Moreover, most of these biochemical parameters can be used as markers to analyze the genetic improvement in the tasar silkworms.

Transgene-based, female-specific lethality system for genetic sexing of the silkworm, Bombyx mori

Transgene-based genetic sexing methods are being developed for insects of agricultural and public health importance. Male-only rearing has long been sought in sericulture because males show superior economic characteristics, such as better fitness, lower food consumption, and higher silk yield. Here we report the establishment of a transgene-based genetic sexing system for the silkworm, Bombyx mori. We developed a construct in which a positive feedback loop regulated by sex-specific alternative splicing leads to high-level expression of the tetracycline-repressible transactivator in females only. Transgenic animals show female-specific lethality during embryonic and early larval stages, leading to male-only cocoons. This transgene-based female-specific lethal system not only has wide application in sericulture, but also has great potential in lepidopteran pest control.

Ras1CA-UpregulatedbcpiInhibits Cathepsin Activity to Prevent Tissue Destruction of theBombyxPosterior Silk Gland

Using the GAL4/UAS transgenic system established in the silkworm, Bombyx mori, we have previously reported that overexpression of the Ras1(CA) oncogene specifically in the posterior silk gland (PSG) resulted in improved fibroin synthesis, silk yield, and other phenotypic effects. However, the detailed molecular mechanism remains to be fully elucidated. Using 2D-DIGE-MS/MS analyses, we compared the proteomic profiles of PSGs from the wild type (WT) and Ras1(CA)-overexpressed silkworms. Among the 24 Ras1(CA)-enhanced proteins, the Bombyx cysteine protease inhibitor (BCPI) was increased 2.4-fold at the protein level and 3.4-fold at the mRNA level. Consistent with the developmental profiles, injection of recombinant BCPI into the WT silkworms at the early wandering stage inhibited cathepsin activity, prevented tissue destruction of the PSG, and delayed pupation. Moreover, injection of small-molecule inhibitors of cathepsin into the WT silkworms prevented PSG destruction and delayed pupation, confirming the role of BCPI in inhibiting cathepsin activity. Furthermore, injection of chemical inhibitors of the Ras downstream effectors into the Ras1(CA)-overexpressed and WT silkworms revealed that both Raf-MAPK and PI3K-TORC1 pathways were required for Ras1 to induce bcpi expression. Taken together, we conclude that via the downstream Raf-MAPK and PI3K-TORC1 pathways, Ras1(CA) upregulates bcpi, which inhibits cathepsin activity thus preventing PSG destruction in Bombyx.

Silk Productivity and Yield Related Characters of Selected Pure Races of Mulberry silkworm, Bombyx mori L.

Experiment was conducted to study the cocoon, biological and yield related characters of selected pure races of Bombyx mori L. Among the multivoltine races, significantly higher cocoon, biological and yield related characters were observed in AGL3 and low in Pure Mysore. Among the bivoltine races, significantly higher characters were observed in CSR2 and low in NN6D. The silk productivity had significant positive correlation with the cocoon and yield related characters whereas fifth instar larval duration, cocoon length and breadth ratio, and renditta were negatively correlated, among all the 10 pure races tested.

Titanium dioxide nanoparticles relieve biochemical dysfunctions of fifth-instar larvae of silkworms following exposure to phoxim insecticide

Phoxim insecticide is widely used in agriculture, which is toxic to insect pests and nontarget organisms. The phoxim poisoning is hard to prevent for silkworms. TiO2 NPs have been widely applied in whitening, brightening foods, toothpaste or sunscreens, and orally-administered drugs. However, whether TiO2 NPs can increase resistance of silkworm to phoxim poisoning has not been reported. The results demonstrated that added TiO2 NPs significantly decreased reduction of protein, glucose and pyruvate contents, lactate dehydrogenase, succinate dehydrogenase and malate dehydrogenase activities, and attenuated increases of free amino acids, urea, uric acid and lactate levels, activities of protease, alanine aminotransferase and aspartate aminotransferase in the hemolymph of silkworms caused by phoxim exposure. From the present study, it is clearly evident that added TiO2 NPs may relieve toxic impacts of phoxim insecticide on silkworm metabolism, which in turn may result in an increase in silk yield.

Comparing the rheology of mulberry and “wild” silkworm spinning dopes

Lepidoperan silks provide a superb opportunity for comparative studies of spinning and fiber characteristics. Comparing the four species, Bombyx mori (China), Actias selene (India), Antheraea yamamai (Japan), Gonometa postica (Africa), allows us to examine differences on the family, species, and race levels. Measured rheological properties were consistent with phylogenetic relationships and in the context of resource allocation and gland morphology. We propose that the thorough domestication of the mulberry silkworm B. mori for high silk yield has resulted in a compensatory optimization for spinning efficiency. This is in stark contrast to the wild silkworms, where Saturnids appear to minimize their energetic input toward silk output and G. postica seems to balance both. We conclude that comparative studies provide valuable baseline information for future biomimetic applications and modeling, as well as illuminating biologically important details of silk processing.

Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and random amplified polymorphic DNA (RAPD) based genetic variation studies in eri silkworm (Samia cynthia ricini Lepidoptera: Saturniidae)

Four strains of eri, Samia cynthia ricini Lepidoptera: Saturniidae that can be identified morphologically and maintained at North East Institute of Science and Technology, Jorhat were characterized based on their protein profile by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and DNA by random amplified polymorphic DNA (RAPD) technique. Fiber yield was highest in Gs strain. SDS-PAGE profile showed 11 prominent bands in the strains with molecular weight ranging from 35 to 200 kDa together with 28 minor bands with molecular weight ranging from 33 to 210 kDa. Two polypeptides of molecular weight 90 and 110 kDa were absent in both Y and Ys. Eight random primers and one universal primer used for RAPD analysis generated a total of 79 bands, of which 49 were polymorphic. In both SDS-PAGE and RAPD, the UPGMA based dendrogram showed two clusters: cluster 1 included Gs and G, whereas Y and Ys was grouped in cluster 2 by SDS-PAGE analysis but RAPD analysis grouped Ys and G in cluster 1 and Gs and Y in cluster 2. The range of genetic diversity observed among the strains affirms the potentiality of RAPD technique for identification and selection of distant parents for silkworm hybridization for high silk yield. Key words: Genetic variation, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), random amplified polymorphic DNA (RAPD), silkworm, cocoon.