Nitrogen fertiliser underpins modern agriculture but carries heavy environmental costs, from greenhouse gas emissions to water pollution and soil degradation. When nitrogen runs short, crops instinctively divert resources into root growth to forage for nutrients, sacrificing the shoots and grain that farmers actually harvest. The molecular switch controlling this trade-off had never been identified, until a study in Science by researchers at Oxford, Nanjing Agricultural University and the Chinese Academy of Sciences pinpointed a gene called WRINKLED1a.
Rice plants lacking a functional copy of the gene lost the ability to boost root growth under low nitrogen, while plants engineered to overexpress it grew more strongly in both roots and shoots, holding their root-to-shoot ratio steady as nitrogen levels varied. Screening more than 3,000 rice cultivars, the team found a naturally occurring, more strongly expressed version of the gene and crossed it into weaker varieties using conventional breeding rather than genetic modification.
Across three field trials in China's Hainan and Anhui provinces, plants carrying the superior allele yielded 23.7 per cent more under low nitrogen application and 19.9 per cent more under high application. The result offers a rare win-win for food security and the environment: a route to maintaining or raising yields while cutting dependence on synthetic fertiliser, applicable through breeding programmes accessible to growers worldwide.