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Hybrid paddy seed production (A-line / R-line system)

Hybrid rice in India is produced almost entirely by the three-line cytoplasmic-male-sterile (CMS) system. The system requires a male-sterile A-line that serves as the female parent, an isogenic maintainer B-line that multiplies the A-line, and a restorer R-line that re-establishes fertility in the F1 hybrid seed.

Principle

The A-line carries a wild-abortive (WA-type) male-sterile cytoplasm and cannot self-pollinate, so when planted alongside an R-line in a seed production plot, the resulting grain is F1 hybrid seed. The B-line is used in a separate nucleus and breeder seed cycle to multiply the A-line itself. Fertility restoration in the F1 is conferred by Rf genes carried by the R-line.

Implementation

Seed production plots interleave A and R lines in carefully calibrated row ratios (typically 8:2 to 10:2) within isolation distances of at least 100 m from other rice fields. Synchronisation of flowering between A and R is managed with split seeding dates, GA3 sprays to improve panicle exsertion of the A-line, and supplementary pollination by rope-dragging across panicles at anthesis. Progressive seed growers in Andhra Pradesh and Telangana achieve hybrid seed yields above 3 t/ha. Purity of the A-line is now checked with functional markers (RMS-5-WA352) to distinguish CMS plants from maintainer contaminants.

Adoption context

ICAR launched a national hybrid rice network project in December 1989, with ICAR-IIRR (Hyderabad) as the lead institute, perfecting the protocol over three decades. Andhra Pradesh and Telangana together now supply roughly 85% of India's hybrid rice seed, anchoring private-sector hybrids such as Kaveri 468, Mahindra Mp 3030 Plus and Pioneer 27P37 25P35.

Limitations

Hybrid seed is single-use; saved seed segregates and cannot be reused. Seed production is technically demanding, requires skilled rope-dragging labour and is vulnerable to weather at flowering. Cytoplasmic uniformity also raises concerns about exposure to specific pathogens.

See also: Kaveri 468, Mahindra Mp 3030 Plus, Pioneer 27P37 25P35, Sava 7501 Savannah, Vnr 1228 2355.

References

  1. Hybrid Rice Seed Production. ICAR-IIRR Technology Page.
  2. Hybrid Rice Seed Production Technology. ICAR-NRRI Research Bulletin No. 31.