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Context: The Indian Council of Agricultural Research announced that it has developed India’s first fully annotated telomere-to-telomere (T2T) reference genome of pigeonpea (Cajanus cajan L. Millsp.), variety ‘Asha’.
What It Is
A complete, gap-free genome sequence covering every chromosome from one telomere to the other, including the centromeres — as distinct from a draft genome, which leaves gaps in repetitive regions that older sequencing technology could not resolve.
| Parameter | Detail |
|---|---|
| Developed by | ICAR–National Institute for Plant Biotechnology (NIPB), New Delhi |
| Size | 752.65 million base pairs |
| Chromosomes covered | All 11, including centromeres and telomeres |
| Assembly designation | NIPB_CcT2T_4, deposited in the global database NCBI |
Why a T2T Genome Is Different
- A draft genome sequences the readable parts of the DNA and leaves gaps wherever the sequence becomes repetitive — precisely where centromeres and telomeres sit. Short-read sequencing cannot resolve long stretches of near-identical repeats.
- A T2T assembly closes those gaps, reading each chromosome continuously end to end. The 92 contigs for 11 chromosomes indicates near-complete chromosome-level assembly, and the 99.9% transcriptome read alignment is the accuracy check — nearly every RNA sequence maps cleanly onto the assembly.
- Why the gaps mattered: centromeric and repetitive regions govern chromosome segregation, recombination frequency and the behaviour of large gene families — including many disease-resistance genes, which cluster in repeat-rich regions. A breeder working from a draft was effectively blind in exactly the areas where stress-tolerance and resistance traits often reside.
The Institutional Track Record
- 2011 — ICAR–NIPB published the world’s first draft genome of pigeonpea variety ‘Asha’ — the first crop genome sequenced entirely in India.
- 2017 — an improved draft genome was published.
- Now — the fully annotated T2T assembly.
Why Pigeonpea Matters
Popularly known as Arhar or Tur, it is one of India’s most important pulse crops and a major source of dietary protein, central to food and nutritional security. India remains a net importer of pulses.
