Genetic Characterization of Bombyx mori (Lepidoptera: Bombycidae) Breeding and Hybrid Lines With Different Geographic Origins

Abstract

The domesticated silkworm Bombyx mori L. comprises a large number of geographical breeds and hybrid lines. Knowing the genetic structure of those may provide information to improve the conservation of commercial lines by estimating inbreeding over generations and the consequences of excessive use of those lineages. Here, we analyzed the genetic diversity of seven breeds and eight hybrid lines from Eastern Europe and Asia using highly polymorphic microsatellites markers to determine its genetical impact on their use in global breeding programs. No consistent pattern of deviation from Hardy–Weinberg equilibrium was found for most breed and hybrids; and the absence of a linkage disequilibrium also suggests that the strains are in equilibrium. A principal coordinate analysis revealed a clear separation of two silkworm breeds from the rest: one (IBV) originated from India and the other one (RG 90 ) from Romania/Japan. The tendency of the other breeds from different geographic origins to cluster together in a general mix might be due to similar selection pressures (climate and anthropogenic factors) in different geographic locations. Phylogenetic analyses grouped the different silkworm breeds but not the hybrids according to their geographic origin and confirmed the pattern found in the principal coordinate analysis.

Genetic analysis of Indian tasar silkmoth (Antheraea mylitta) populations

“…Among other silkworms the genetic structure of A. assama , a species with a very restricted distribution, has been studied and its populations were found to be reasonably differentiated 18 20 . Different strains and lines of the domesticated silkworm B. mori have also been subjected to this kind of analysis 32 45 46 47 , however these studies are arguably not comparable to wild lepidopteran species.…”

Role of microsatellites in genetic analysis of Bombyx mori silkworm: a review

“…Various pure lines may also share an origin in the same ancestral population of B. mandarina, but would have been selected to express different phenotypes, maintaining a high similarity at the genotypic level 7,37,59 . This might also explain why pure lines with similar characteristics are not always grouped, given that they would have a distant relationship, but would have been selected to express similar traits 35,37 .…”

“…These molecular markers have been a useful tool in sericulture, especially in the management, characterization and conservation of materials in germplasm banks 7,8 and in the development of genetically improved materials 9 . They have been particularly difficult to apply, however, to genetic mapping, mainly due to the low frequency of loci suitable as molecular markers in the B. mori genome.…”

Implications of genetic diversity in the improvement of silkworm Bombyx mori L.

“…It is the main source of silk ("the queen of natural fibers"), contributing around 90% of world production (ISC, 2014). Bombyx mori embraces a large number of geographic breeds, strains and hybrid lines (Furdui et al, 2014) classified (by origin, biological characteristics, and origin of germplasm banks) and preserved with the aim of gradually improving economic interest, to increase the benefits of sericulture and thereby boost silk production efficiency (Tavakolian, 2000). Furdui et al (2014) state that the diversity and structure of B. mori genetic resources can provide information to improve conservation, estimate inbreeding, and determine the consequences of overuse of lineages.…”

“…Bombyx mori embraces a large number of geographic breeds, strains and hybrid lines (Furdui et al, 2014) classified (by origin, biological characteristics, and origin of germplasm banks) and preserved with the aim of gradually improving economic interest, to increase the benefits of sericulture and thereby boost silk production efficiency (Tavakolian, 2000). Furdui et al (2014) state that the diversity and structure of B. mori genetic resources can provide information to improve conservation, estimate inbreeding, and determine the consequences of overuse of lineages. In addition, they allow the optimization of breeding strategies that facilitate the selection of individuals with high genetic potential, emphasizing that nutritional, climatic (temperature, relative humidity, luminosity) and controlled sanitary conditions should be provided in breeding huts (Salehi et al, 2010;Talebi and Bakkappa, 2013;Neshagaran et al, 2016).…”