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Published on: April 12, 2017
Vertical transmission of nucleopolyhedrovirus in the silkworm, Bombyx mori L
A M Khurad1, A Mahulikar, M K Rathod
1Department of Zoology, Nagpur University Campus, Nagpur-440 033, India. csbrnu_ngp@sancharnet.in
Abstract:
Nucleopolyhedrovirus (NPV) was tested for vertical transmission in the silkworm, Bombyx mori. Fifth instar larvae were exposed to four different dosages of BmNPV (830, 1300, 1800, and 2000OBs/larva) and a dosage of about 2000OBs/larva was found suitable for obtaining infected adults. Histopathological studies revealed the infection in susceptible tissues and organs initially, and at later stages of infection cycles the spermatocytes and nurse cells in the young oocytes were infected in the larval rudiments of testis and ovary, respectively. The mating of infected females with uninfected males resulted in significant reduction in fecundity (P < 0.01) and hatching of eggs (P < 0.001) due to transovarial transmission of BmNPV. Mating tests of uninfected females and infected males also confirmed venereal transmission as there was a significant reduction in hatching of eggs (P < 0.01). Further, among the F1 hybrid offspring (infected female x uninfected male) that were infected transovarially, larval progeny died at first and second instar stages, whereas those infected venereally developed acute lethal infection late and died by the end of third and fourth instar stage. PCR amplification and sequencing of 473bp of immediate early-1 (ie-1) gene of BmNPV isolated from the viral-infected parent and the F1 offspring confirmed that the viral infection is vertically transmitted to the progeny.
Insights
The silkworm, Bombyx mori, can transmit nucleopolyhedrovirus (NPV) vertically. This study confirms both transovarial and venereal transmission of BmNPV, impacting offspring survival and demonstrating viral inheritance.
Area of Science:
- Entomology
- Virology
- Genetics
Background:
- Nucleopolyhedrovirus (NPV) poses a threat to silkworm (Bombyx mori) populations.
- Understanding viral transmission routes is crucial for disease management in sericulture.
Purpose of the Study:
- To investigate the vertical transmission of Bombyx mori nucleopolyhedrovirus (BmNPV) in silkworms.
- To determine the effects of BmNPV infection on fecundity, egg hatching, and offspring survival.
- To confirm the genetic basis of vertical BmNPV transmission.
Main Methods:
- Fifth instar silkworm larvae were exposed to varying dosages of BmNPV.
- Histopathological examination of infected tissues and reproductive organs.
- Mating experiments involving infected and uninfected silkworms.
- Polymerase Chain Reaction (PCR) amplification and sequencing of the BmNPV ie-1 gene.
Main Results:
- A dosage of approximately 2000 OBs/larva enabled the production of infected adults.
- BmNPV infected spermatocytes and nurse cells in larval reproductive organs.
- Transovarial and venereal transmission significantly reduced fecundity and egg hatching rates.
- Offspring infected transovarially died earlier (instars 1-2) than those infected venereally (instars 3-4).
- PCR confirmed the presence of the BmNPV ie-1 gene in both parent and offspring.
Conclusions:
- BmNPV is efficiently transmitted vertically from parent to offspring in Bombyx mori through both transovarial and venereal routes.
- Vertical transmission of BmNPV leads to reduced reproductive success and increased larval mortality.
- The study provides molecular evidence confirming vertical transmission of BmNPV.
