A silkworm's genetic diary
The silkworm, Bombyx mori, is an insect completely reliant on humans for its survival. It cannot fly, has poor vision, and lacks the camouflage of its wild ancestor, Bombyx mandarina. This dependency is the result of at least 5,000 years of selective breeding that began in China. This long history of domestication has left clear marks on the silkworm's genome. Compared to its wild relative, B. mori has a larger body, grows faster, and produces a significantly bigger cocoon. This process also reduced its genetic diversity by 33-49% compared to wild populations, a common effect of domestication.
The story of how this domesticated insect spread from China is written in its DNA. Phylogenetic analysis confirms that silkworm populations in Uzbekistan have a close genetic relationship with those in China, indicating they were introduced via the ancient Silk Road. Mitochondrial DNA (mtDNA), which is inherited maternally, is a powerful tracer for these ancient routes. The mtDNA of silkworms in the Boysun region shows that their ancestors were Chinese silkworms brought to this area around 1,700 years ago. These lineages established a new center for sericulture far from its origin point.
Local adaptation in Boysun
Once established in what is now Uzbekistan, the imported Chinese silkworms did not remain static. Over centuries, local farmers selected for traits that were best suited to the specific environmental conditions of the Surkhandarya region. This long-term artificial selection led to the development of unique local strains. These strains adapted to the regional climate and the specific chemistry of the local mulberry leaves, the exclusive food of silkworm larvae.
Genetic studies comparing Chinese and Uzbek silkworm populations reveal these distinct evolutionary paths. While the foundational genetics are Chinese, the Uzbek varieties possess unique traits and genetic markers. This demonstrates a classic pattern of domestication: a founding population from a single origin spreads to a new location, followed by diversification and adaptation. The silk produced in Boysun today comes from this deep history, connecting modern workshops to the ancient traders who first carried their precious, silk-producing cargo across the continent. This legacy continues; Uzbekistan remains a significant producer of silk cocoons and silkworm eggs.