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CSR bivoltine races: CSR2, CSR4 and the CSR2 x CSR4 hybrid Photo: Anil Sharma · Pexels License · source ↗

CSR bivoltine races: CSR2, CSR4 and the CSR2 x CSR4 hybrid

The CSR series is a family of bivoltine silkworm (Bombyx mori) races developed at the Central Sericultural Research and Training Institute (CSRTI) Mysore under the Central Silk Board between 1985 and 2000. CSR2 and CSR4 are the two productive parental lines, and their cross — CSR2 x CSR4 — is the single most widely reared bivoltine hybrid in tropical India. The CSR programme delivered, for the first time, bivoltine races that yield consistently under the warm, fluctuating climate of South India, where earlier Japanese-origin bivoltines had failed.

Origin and parentage

CSR2 and CSR4 were selected at CSRTI Mysore from a four-line breeding pool that included European and Japanese-origin bivoltine ancestors. Both lines were stabilised through 30+ generations of selection for cocoon weight, shell ratio, hatchability and tropical-tolerance traits. CSR2 and CSR4 were notified as authorised bivoltine races by the Central Silk Board in 1996. Sibling races in the series include CSR5, CSR6, CSR16, CSR17, CSR18 and CSR19 — used both as parents (e.g., CSR18 x CSR19) and reciprocally crossed with CSR2 and CSR4.

Race characteristics

CSR2 produces white, oval cocoons with a shell ratio of 24-25% and cocoon weight of 1.8-2.0 g. CSR4 produces white, dumb-bell-shaped cocoons with a shell ratio of 23-24% and cocoon weight of 1.9-2.0 g. The CSR2 x CSR4 hybrid combines the cocoon weight of CSR4 with the shell quality of CSR2 and is notable for:

  • Cocoon weight: 2.0-2.2 g per cocoon
  • Shell ratio: 23-24%
  • Raw silk recovery: 18-20%
  • Renditta: 6.5-7.5 kg of cocoons per kg of raw silk
  • Filament length: 1,000-1,200 metres per cocoon
  • Silk grade: 3A to 4A
  • Larval duration: 24-26 days at 25-26°C and 75% RH

Rearing requirements

CSR hybrids require certified disease-free layings (Disease Free Layings Dfl) from licensed grainages and chawki rearing in a controlled environment (Chawki Rearing Centre) for the first two instars. Late-instar worms are reared on V-1 mulberry leaf (Mulberry Variety V1 Victory 1) with whole-shoot feeding under temperature of 23-25°C and humidity of 70-85%. Strict bed disinfection with bleaching powder, vijetha or sanitech is required between batches, and chlorination of shoots before each feeding controls fungal and viral build-up. The race is more sensitive than crossbreed races to leaf-quality variation and rearing-room hygiene.

Disease profile

Compared with the older crossbreed (CB) races, CSR2 x CSR4 has somewhat higher susceptibility to grasserie (BmNPV) and flacherie when rearing temperatures rise above 28°C or humidity falls below 60% (Grasserie Flacherie Silkworm Diseases). Strict ambient control during summer rearing batches is the single most important crop-loss preventive.

Adoption and market

CSR2 x CSR4 supplies almost the entire bivoltine cocoon volume sold through Central Silk Board-regulated auction markets at Ramanagara (Karnataka), Hindupur and Anantapur (Andhra Pradesh), Salem (Tamil Nadu) and Sidlaghatta (Karnataka) (Cocoon Marketing Csb Auction). Reeler bids for 3A-4A grade CSR cocoons typically run 30-50% above CB cocoon prices, which keeps the hybrid in commercial dominance despite its higher management demands.

See also: Bivoltine Silkworm, Mulberry Variety V1 Victory 1, Chawki Rearing Centre, Grasserie Flacherie Silkworm Diseases, Cocoon Marketing Csb Auction.

Sources

  1. Bivoltine Silkworm Breeds Developed at CSRTI Mysore. Central Silk Board.
  2. CSR Bivoltine Hybrids. SILKS portal, Central Silk Board.
  3. Productive Bivoltine Hybrids for Tropical Sericulture. Journal of Innovative Research and Reviews.