Rice breeding lines that combine four separate drought-tolerance genes have yielded 36 to 82 per cent more than their parent variety under water stress, Indian researchers report in the Indian Journal of Genetics and Plant Breeding. The lines were made by conventional marker-assisted crossing, not genetic engineering, so they face none of the regulatory hurdles that have kept GM food crops out of Indian fields.

The work was carried out by scientists at Malla Reddy University in Hyderabad, the ICAR-Indian Institute of Rice Research, Central Agricultural University in Umiam and the ICAR-National Institute for Plant Biotechnology in New Delhi. They evaluated 40 breeding lines developed by QTL pyramiding, in which several genetic regions linked to one trait are brought together in a single plant; the lines carried combinations of the drought-tolerance QTLs qDTY1.1, qDTY2.1, qDTY2.2 and qDTY3.1.

Five lines stood out — QTV 108-4, QTV 108-3, QTV 189-2, QTV 128-4 and QTV 105-1 — with grain-yield gains of 36 to 82 per cent over the unmodified DRR Dhan 50 when subjected to drought stress. The researchers also measured high heritability and genetic advance for the traits behind that performance, which suggests the gains should carry through to later generations under ordinary selection.

The study found spikelet fertility and harvest index to be the two secondary traits most closely tied to protecting yield under water shortage, giving breeders measurable targets to select for rather than waiting for end-of-season yield. Principal component analysis showed the first two components explained close to half the genetic variation among the 40 lines, leaving useful diversity for further refinement.

Because QTL pyramiding uses marker-assisted conventional breeding, the resulting varieties avoid the biosafety approvals and public-acceptance questions that surround transgenic or gene-edited crops. India has approved only one GM crop, Bt cotton, and no GM food crop, which makes conventional routes like this one the main path to climate-resilient rice there.

Rainfed rice grown without assured irrigation covers vast areas of eastern and central India and large parts of Africa and Southeast Asia, where dry spells are among the biggest constraints on farm income. The findings land in a kharif season in which several Indian states have reported large rainfall deficits — exactly the years these lines are bred for.

Source: AgroPages