Sensitivity of Polyvoltine Thai Strains of Bombyx mori to a BmNPV Isolate From Mahasarakham.

Olle Terenius,Siripuk Suraporn

doi:10.1093/jisesa/ieaa023

Abstract

Virus infection by the Bombyx mori nucleopolyhedrovirus (BmNPV) is the most severe disease in Thai sericultural practice of polyvoltine silkworms. Here, we characterized a newly isolated BmNPV isolated from the Mahasarakham province in Thailand (BmNPV-MSU). The purity and morphology of BmNPV-MSU were examined using light microscopy and scanning electron microscopy. The polyhedral inclusion bodies (PIBs) of BmNPV-MSU appeared in tetragonal, hexagonal, octagonal, and globular forms. The virions were both single and multiple embedded as observed by transmission electron microscopy. We also determined the virulence of BmNPV-MSU for six different Thai polyvoltine strains by LC50 and time to death after infection. The LC50 values of Nang Lai, NK04, and Sam Rong strains were 5.05–1.52 × 107 PIBs per ml and mortality peaked 7- to 8-d after inoculation. For Nang Noi, SP2, and RE05 strains the LC50 values were 7.91–1.82 × 106 PIBs/ml and mortality peaked 4–5 d after inoculation, thus having lower chance of survival to infection by BmNPV-MSU.

Highlights

Virus infection by the Bombyx mori nucleopolyhedrovirus (BmNPV) is the most severe disease in Thai sericultural practice of polyvoltine silkworms
We determined the virulence of BmNPV-Mahasarakham University (MSU) for six different Thai polyvoltine strains by LC50 and time to death after infection.The LC50 values of Nang Lai, NK04, and Sam Rong strains were 5.05–1.52 × 107 polyhedral inclusion bodies (PIBs) per ml and mortality peaked 7- to 8-d after inoculation
Even though BmNPV is the key pathogen in sericultural practices in Thailand causing significant yield loss, there are no reports of Thai silkworm strains that are resistant to BmNPV

Summary

Introduction

Virus infection by the Bombyx mori nucleopolyhedrovirus (BmNPV) is the most severe disease in Thai sericultural practice of polyvoltine silkworms. We determined the virulence of BmNPV-MSU for six different Thai polyvoltine strains by LC50 and time to death after infection.The LC50 values of Nang Lai, NK04, and Sam Rong strains were 5.05–1.52 × 107 PIBs per ml and mortality peaked 7- to 8-d after inoculation. For Nang Noi, SP2, and RE05 strains the LC50 values were 7.91–1.82 × 106 PIBs/ml and mortality peaked 4–5 d after inoculation, having lower chance of survival to infection by BmNPV-MSU.

Results

Conclusion