Patterns in Genotype Composition of Indian Isolates of the Bombyx mori Nucleopolyhedrovirus and Bombyx mori Bidensovirus.

Mudasir Gani,Vankadara Sivaprasad,Johannes A Jehle,Rakesh Gupta,Pawan Saini,Jörg T Wennmann,Kamlesh Bali,Sergei Senger,Satish Lokanath

doi:10.3390/v13050901

Abstract

The mulberry silkworm, Bombyx mori (L.), is a model organism of lepidopteran insects with high economic importance. The viral diseases of the silkworm caused by Bombyx mori nucleopolyhedrovirus (BmNPV) and Bombyx mori bidensovirus (BmBDV) inflict huge economic losses and significantly impact the sericulture industry of India and other countries. To understand the distribution of Indian isolates of the BmNPV and to investigate their genetic composition, an in-depth population structure analysis was conducted using comprehensive and newly developed genomic analysis methods. The seven new Indian BmNPV isolates from Anantapur, Dehradun, Ghumarwin, Jammu, Kashmir, Mysore and Salem grouped in the BmNPV clade, and are most closely related to Autographa californica multiple nucleopolyhedrovirus and Rachiplusia ou multiple nucleopolyhedrovirus on the basis of gene sequencing and phylogenetic analyses of the partial polh, lef-8 and lef-9 gene fragments. The whole genome sequencing of three Indian BmNPV isolates from Mysore (-My), Jammu (-Ja) and Dehradun (-De) was conducted, and intra-isolate genetic variability was analyzed on the basis of variable SNP positions and the frequencies of alternative nucleotides. The results revealed that the BmNPV-De and BmNPV-Ja isolates are highly similar in their genotypic composition, whereas the population structure of BmNPV-My appeared rather pure and homogenous, with almost no or few genetic variations. The BmNPV-De and BmNPV-Ja samples further contained a significant amount of BmBDV belonging to the Bidnaviridae family. We elucidated the genotype composition within Indian BmNPV and BmBDV isolates, and the results presented have broad implications for our understanding of the genetic diversity and evolution of BmNPV and co-occurring BmBDV isolates.

Highlights

The silk moth, Bombyx mori (L.), is an economically and culturally important insect that is domesticated for silk production, mainly in China and India [1]
Due to the phylogenetic separation within the Indian Bombyx mori nucleopolyhedrovirus (BmNPV) clade and the distance between their geographic origins, the isolates of BmNPV-My, BmNPV-De and BmNPVJa (Figure 2b) were selected for whole genome sequencing, which led to the de novo assembly of a BmNPV-My contig of 127,582 bp in length that encompassed the entire circular BmNPV genome
Due to the phylogenetic separation within the Indian BmNPV clade and the distance between their geographic origins, the isolates of BmNPV-My, BmNPV-De and BmNPV-Ja (Figure 2b) were selected for whole genome sequencing, which led to the de novo assembly of a BmNPV-My contig of 127,582 bp in length that encompassed the entire

Summary

Introduction

The silk moth, Bombyx mori (L.), is an economically and culturally important insect that is domesticated for silk production, mainly in China and India [1]. Domestic mass rearing of silk moth is highly labor-intensive and usually handled by local farmers, who continuously rear larvae from hatching to pupation with the only available food source, the leaves of the mulberry plant [2,3]. The pupating larvae produce cocoons from which silk thread can be harvested. The major constraints for increased cocoon yield in sericulture are the occurrence of diseases such as grasserie, flacherie, muscardine and pebrine caused by virus, bacteria, fungi and microsporidia infection, respectively [4,5,6]. Viruses are considered the most important pathogens in silk moth rearing, causing serious and significant economic damage, and posing a serious threat to global sericulture [7]. Silkworm losses due to diseases in India are about 15–20%, of which more than 50% are attributed to viral infection only [8]

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Results

Conclusion