Silk, often referred to as the “queen of fibres”, has been valued for its beauty and luxury throughout history. It is unrivalled in its appearance and texture, making it a highly prized material across the globe. Silk’s allure doesn’t stop at its aesthetic appeal; researchers have recently unveiled genetic factors behind the cocoon colors and adaptations of silk-producing insects, offering compelling insights into how this industry has evolved.
The Role of Cocoons in Silk Production
A cocoon is a protective layer of silk thread spun by a silkworm around itself. This thread is remarkably fine yet strong, boasting an impressive lustre. Cocoon shapes tend to be oval or round. Unwinding the thread from these cocoons and weaving it enables the creation of exquisite silk fabric.
Discovering Genetic Clues in Silk Moths
Looking at the evolution of silk moth domestication uncovers fascinating genetic insights. Domesticated silk moths (Bombyx mori) originated over 5,000 years ago in China, evolving from wild silk moths (Bombyx mandarina). Despite domesticated silk moths flourishing worldwide, their wild ancestors still roam parts of Asia like China, Japan, Korea, and far-eastern Russia.
Understanding the Different Types of Silk
From a global perspective, there are different types of silk, each with unique characteristics. Non-mulberry or ‘wild’ silks, including muga, tasar, and eri silks, are derived from caterpillars of moth species Antheraea assama, Antheraea mylitta, and Samia cynthia ricini. Caterpillars that produce non-mulberry silks feed on a wider variety of trees, and their silk strands are shorter, coarser, and harder than those of mulberry silk.
Mulberry silk is the most common type of silk, accounting for about 90% of global silk production. This silk originates from the domesticated mulberry silkworm (Bombyx mori), which feeds exclusively on mulberry leaves. It has long, smooth, and lustrous fibers perfect for weaving or knitting into various fabrics with different textures and finishes.
Decoding Cocoon Colors: Carotenoids and Flavonoids
Silkworm cocoons come in a variety of colours due to pigments derived from carotenoids and flavonoids. The silkworms absorb these chemical compounds from the mulberry leaves they feed on and transport them to the silk glands. Here, these pigments bind to the silk protein, influencing the color of the silk threads spun to form cocoons. Interestingly, genetic mutations affecting carotenoids and flavonoids lead to differently colored cocoons – a phenomenon that elucidates the molecular basis of silk diversity.
The Current State of India’s Silk Industry
India is the world’s second-largest producer of raw silk after China, boasting a production of 33,739 MT in 2020-2021. The country produces a diverse range of silk types, thanks to the distinct feeding habits of different silkworm species. Silk production is a significant foreign exchange earner for India, contributing considerably to the country’s economy.
In the 2021-2022 fiscal year, Karnataka led India’s silk production, contributing 32%. Other significant contributors include Andhra Pradesh, Assam, Bihar, Gujarat, and West Bengal. Furthermore, India exports silk to over 30 countries worldwide, with top importers being the USA, UAE, China, UK, Australia, and Germany.
The sericulture industry in India employs nearly 9.76 million people across 52,360 rural and semi-urban villages. The Central Silk Board, established in 1948, oversees this industry, promoting its development through research, training, quality control, and marketing support.
The central government has also launched initiatives like “Silk Samagra” and the “North East Region Textile Promotion Scheme (NERTPS)” to support the sericulture sector. The latter specifically focuses on reviving, expanding, and diversifying the production of Eri and Muga silks in North Eastern states.