• Journal of Sericultural and Entomological Science
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• v.32 no.1
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• pp.44-48
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• 1990

Monoclonal antibodies were prepared against Bombyx densonucleosis virus type-II(Yamanashi isolate). Four hybridoma clones, named C4, Fl, H2, M9 were only reacted with the DNV-II, but those were not reacted with Bombyx densonucleosis virus type-I(Ina isolate) and infectious flacherie virus(IFV) by double diffusion test in 0.8% agarose gel. C4, Fl and M9 of them were reacted with 53KDa polypeptide of DNV-II, and H2 was reacted with 46. 5KDa polypeptide of the virus.

• International Journal of Industrial Entomology and Biomaterials
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• v.9 no.1
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• pp.35-40
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• 2004

Bombyx mori densonucleosis virus type 1 (BmDNV1)- a non occluded virus causes flacherie disease in the susceptible stocks of the silkworm, Bombyx mori. However, some stocks are non-susceptible. Non-susceptibility to BmDNV1 in B. mori is a unique case where the virus infection is completely inhibited by a single gene of the host. A survey conducted by this institute in some parts of Karnataka state has revealed that, 43.05% of the total incidence of flacherie disease caused by non-occluded viruses, are due to the synergistic infection of B. mori densonucleosis and infectious flacherie virus. Earlier study indicated that rearing of BmDNV1 resistant silkworm stock is effective in protecting silkworm against BmIFV also. In the present study the response of 78 silkworm stocks which include 42 of non-diapausing and 36 of diapausing groups, to BmDNV1 is investigated. Newly ecdysed third instar larvae were inoculated per-os with 10% inoculum of BmDNV1 extracted from the mid-gut of infected silkworm. One non-diapausing and three diapausing silkworm stocks were found to be resistant to BmDNV1. Eleven silkworm stocks were found to possess moderate resistance whereas rest sixty three were found to be susceptible to BmDNV1. Genetic analysis has shown that the resistance to BmDNV1 is autosomally inherited and controlled by a major dominant or a major recessive gene in different silkworm stocks. These resistant stocks can be utilized as the resource material to develop BmDNV1 resistant commercial hybrids. The selection strategies, depending upon the mode of inheritance of resistance in the resource material chosen, are discussed.

• International Journal of Industrial Entomology and Biomaterials
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• v.6 no.2
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• pp.145-149
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• 2003

Seeing inadequate disinfection and unhygenic condition in rearing area, use of disease resistant silkworm variety is the best option. In order to this, an attempt has been made to develop the resistance to Bombyx mori densonucleosis virus (BmDNV-2) into a susceptible silkworm breed Zhenon1 by cross breeding with a resistant silkworm breed SU12 and exposing the subsequent generations to BmDNV-2 followed by the selection of individuals from the surviving batches. After seven generation the evolved DNV-2 resistant strain showed the significantly higher resistance to BmDNV-2 than control Zhenon1. The economic characters of both of the breeds were almost on par.

• Journal of Sericultural and Entomological Science
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• v.34 no.2
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• pp.26-31
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• 1992

Flacherie virus (FV) and Densonucleosis virus (DNV) of the silkworm, Bombyx mori, which give the most severest damage to the silk production in korea, were fed on the mulberry wild silkworm, Bombyx mori mandarina, the mulberry pyralid, Gryphodes phyloalis, and the American fall webworm, Hypantria cunea, to investigate cross infectivity by serological and histopathological at observation. By the Ouchterlony's double difusion test the mulberry wild silkworm was infected with both FV and DNV type 1 (DNV-1) and the mulberry pyralid with DNV-1, so those were confirmed the cross infection. But the American fall webworm was not recognized the cross infection by the same method. The infection and multiplication of the FV in the mulberry wild silkworm was observed in the cytoplasm of the goblet cell with the appearance of the virus-specific vesicle. In DNV-1 infection to the mulberry wild silkworm and the mulberry pyralid, the nuclei of columnar cell in the midgut of both insects was hypertrophied and the nuclei of midgut cell of the mulberry pyralid positively stained with the feulgen stain. Multiplication of DNV-1 in the midgut cell of the mulberry wild silkworm was replicated in two different patterens as linear arrays and large masses, while that of DNV-1 in the muberry pyralid was multiplied as virus masses in several portion of the nuclei of the midgut cell.

• Journal of Sericultural and Entomological Science
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• v.28 no.2
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• pp.48-51
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• 1986

Resistance to the flacherie virus(FV) and the densonucleosis virus(DNV) of 10 Japanese lines and 10 Chinese lines used for hybrids was tested and the results obtained are as follows ; 1. Hansang #1 showed the highest resistance to the FV among the tested Japanese lines whereas Mudeung was of lowest resistance. In Chinese lines tested on the resistance to the FV, Jam118 was the highest while Jam 116 was the lowest. 2. In Japanese lines tested on the resistance to the DNV, it was shown that Jam 117, Gyeongchy, Mudeung, Hansaeng #1 and Hansaeng #3 were of the complete resistance but Jam 115 showed the lowest resistance. On the other hand, all the Chinese lines tested showed the complete resistance to the DNV.

• International Journal of Industrial Entomology and Biomaterials
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• v.11 no.2
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• pp.135-138
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• 2005

Two pairs of DNA primers were designed for the detection of the Zhenjiang (China) strain of Bombyx mori densonucleosis virus (BmDNV-Z). These primers were designed from the nucleotide sequence of major structural protein gene (putative VD1-ORF2). PCR amplification was attempted from different issues (including silk gland, blood, skin and midgut) and feces of the silkworm which infected wit BmDNV-Z were amplified by PCR. Both of the primers gave expected size of in the DNA bands from midgut and feces, but not in the DNA of silk gland, blood and skin. The two bands were sequenced, and their sequence were same as the sequence designed for. BmDNV-Z could be successfully detected in single silkworm after it was infected for 12 hrs, and could not be detected before 9 hrs after infected.

• Journal of Sericultural and Entomological Science
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• v.25 no.2
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• pp.1-31
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• 1984

Flacherie, as one of the most prevalent silkworm diseases, causes severe economic damage to sericultural industry and its pathogens have been proved to be flacherie virus (FV) and densonucleosis virus (DNV). Multiplications of the viruses in the larvae of the silkworm, Bombyx mori, were studied by the sucrose density gradient centrifugation and electron microscopy. The quantitative and qualitative changes of nucleic acids and proteins were investigated from the midgut and hemolymph in the silkworm larvae infected separately with FV and DNV. The histopathological changes of epithelial cells of infected midgut also were examined by an electron microscope. 1. Purified fractions of FV or DNV in a sucrose density gradient centrifugation yielded one homogenous and sharp peak without a shoulder, suggesting no heterogenous materials in the preparation. Electron microscopy also revealed that FV and DNV were spherical particles, 27nm and 21nm in diameter, respectively. 2. Silkworm larvae showed a decrease in body weight on the 6th day and in midgut weight on the 3rd day after inoculation with FV or DNV. 3. DNA content was higher in the midgut when infected with FV or DNV, but the hemolymph of the infected larvae showed no difference during first 6 days after inoculation, after which DNA concentration declined rapidly. 4. RNA synthesis of silkworm larvae infected separately with FV and DNV was stimulated in the midgut, but RNA content was reduced in the hemolymph at the early stage of virus multiplication. At the late stage of virus multiplication, however, it was extremely reduced in both midgut and hemolymph. 5. The concentration of protein in the midgut and hemolymph of silkworm larvae infected separately with FV and DNV showed no difference from that of the healthy larvae at the early stage of virus multiplication, but it was significantly reduced at the late stage of virus multiplication. 6. There was no difference in the electrophoretic patterns of RNAs extracted from the midgut of healthy or virus-infected larvae. 7. The electrophoresis of proteins extracted from the midgut infected with FV or DNV, when carried out on the 1st and 5th day after virus inoculation, showed no difference from that of the healthy larvae. But, there was an additional band with medium motility in the proteins on the 8th day after virus inoculation, while a band with low mobility shown in the proteins of healthy larvae disappeared in the infected larvae. However, a band with high mobility in the healthy larvae was separated into two fractions in the infected larvae. 8. The electrophoretic pattern of hemolymph proteins of the silkworm larvae infected separately with FV and DNV was similar to that of the healthy larvae, but the concentration of hemolymph proteins in the infected larvae was lower than that of the healthy larvae at the late stage. 9. Two types of inclusion bodies were shown by the double staining of pyronin-methyl green in the columnar cell of the midgut on the 8th day after FV inoculation. 10. Electron microscopy of the infected midgut revealed that the 'cytoplasmic wall' of the goblet cell thickened on the 5th day after FV inoculation and several types of the cytopathogenic structures, such as virus$.$specific vesicles, virus particles, linear structures, tubular structures, and high electron-dense matrices were observed in the cytoplasm of the goblet cell. The virus particles were also observed in the microvilli and the structures similar to spherical virus particles were observed around the virus-specific vesicles, suggesting the virus assembly in the cytoplasm. 11. Fluorescence micrograph of the infected midgut stained with acridine orange showed that the nucleus, the site of DNV multiplication in the columnar cell, enlarged on the 5th day after virus inoculation. 12. Electron microscopic examination of DNV infected midgut revealed that the nucleolus of the columnar cell was broken into granules and those granules dispersed into apical region of the nucleus on the 5th day after virus inoculation. On the 8th day after inoculation, it was also observed that the nucleus of the columnar cell was full with the high electron-dense virogenic stroma which were similar to virus particles. These facts suggest that the virogenic stroma were the sites of virus assembly in the process of DNV multiplication.

• International Journal of Industrial Entomology and Biomaterials
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• v.13 no.2
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• pp.109-112
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• 2006

The use of commercial silkworm hybrids resistant to important silkworm diseases is economical and better option particularly in tropical areas. This necessitated the evolution of productive bivoltine silkworm breeds non-susceptible to $BmDNV_1$. Non-susceptibility to $BmDNV_1$, infection was found to be controlled by a single recessive gene, nsd-l or a dominant gene, Nid-l. A major dominant/recessive gene confers resistance to $BmDNV_1$, from potent donor parents have been transferred to 10 productive but susceptible bivoltine silkworm strains through conventional breeding methods. By utilizing these breeds prepared 25 hybrids $(5{\times}5)$ and hybrid evaluation was carried out to identify most promising hybrids resistant to $BmDNV_1$. All these hybrids are inoculated with $BmDNV_1$ inoculum along with productive control hybrid $CSR2{\times}CSR4$ and reared under standard rearing procedure. Based on inoculated rearing and test reeling results, two most promising hybrids $(CSR18DR{\times}CSR29DR\;and\;CSR21DR{\times}CSR50DR)$ were selected for commercial exploitation. The selected hybrids have shown a survival rate of >85% with productive traits, where as control hybrid have shown 11.1% survival with inferior cocoon traits. The methodologies adopted were discussed.

• International Journal of Industrial Entomology and Biomaterials
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• v.13 no.2
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• pp.73-77
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• 2006

Combining ability and hybrid vigour analysis was carried out in hybrids between newly developed non-susceptible lines to BmDNV1 and popular bivoltine breeds for certain quantitative traits viz. Pupation rate, Cocoon yield, Cocoon weight, Cocoon shell weight and Cocoon shell ratio, Survival rate against BmIFV and BmNPV. General combining ability (GCA) effects revealed that among the lines CSR2DR was found good general combiner exhibiting significant GCA effects for six characters, out of seven traits evaluated. Among testers CSR28DR was found as good combiner exhibiting significant GCA effects for six traits. Out of 36 hybrids made between $resistant{\times}resistant,\;resistant{\times}susceptible\;and\;susceptible{\times}susceptible$ breeds, one hybrid $CSR21DR{\times}CSR28DR$ exhibited significant SCA effects for six traits. The selected hybrid $CSR21DR{\times}CSR28DR$ also exhibited significant positive heterosis and heterobeltiosis expressions for maximum traits and could be exploited as commercial silkworm hybrid resistant to important viral diseases.

• Journal of Sericultural and Entomological Science
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• v.33 no.1
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• pp.13-20
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• 1991

The flacheric virus(FV) was isolated from the diseased larvae with flaccidity symptoms of the silkworm, Bombyx mori, which were collected in Hyangnam, Kyunggi Province and in Youcheon, Kyungpook Province. The properties of the virus were investigated and compared with the Japanese FV in morphology, size, nucleic acid and structural proteins. The Hyangnam isolate had a diameter of 27$\pm$1, 7nm with speherical shape and contained RNA of which the electrophoretic pattern was same as that of the Japanese FV. The virus had four sturctural proteins and their molecular weight were estimated as 35, 000, 33, 000, 31, 000, and 11, 400 daltons, respectively. The Youcheon isolate had two different sizeds in diameter of 27$\pm$1.7nm and 21$\pm$0.8nm. The antigenicity of the Hyangnam isolate was proved to be identical to that of Japanese FV, whereas the antisera against the Youcheon isolate (mixed with two different sizes) reacted with Japanese FV and densonucleosis virus type 1, respectively. From these characteristic of the isolated viruses, it was concluded that the Hyangnam isolate was identical to the Japanese FV and the Youncheon isolate contained the same viruses as the Japanese FV and DNVI.