Rice cultivation suffers from a nitrogen problem. Modern rice relies heavily on fertilizers. This reliance helped drive the Green Revolution and the astonishing rise in revenues that followed. It also made agriculture an expensive habit. Growers need nitrogen to increase production, but less than half of what is applied to the field ends up inside the plant. The rest is lost to the air, water and soil, with consequences for farm budgets, pollution and climate. In India, where annual fertilizer subsidy amounts to approximately Rs 1.7 million, any credible path to using less nitrogen without sacrificing revenues is a step towards sustainable food security.
A new study in Science by researchers at Nanjing Agricultural University, the University of Oxford, and the Chinese Academy of Sciences suggests one such path. The team, led by Qingbo Chen, Zhi Jie, and Shan Li, has identified a rice gene that helps the rice plant maintain its balance when nitrogen is scarce. In field trials, plants carrying a naturally stronger version of this gene produced yields about 24 percent higher under low fertilizer conditions, and about 20 percent higher under high fertilizer conditions.
The story begins with a basic plant dilemma. When nitrogen runs out, the rice plant goes into survival mode. It diverts energy to the roots to search for nutrients and reduces the shoots from which the grains come. In the wild, this makes sense. But in a monoculture rice field, where all the neighboring plants are doing the same thing underground, it’s less than ideal. Less bud growth usually means lower yield.
Read also:Scientifically speaking: AI writes code and changes jobs. Who actually benefits?
Scientists have known about this trade-off for more than a century. What they didn’t find was the biological genetic switch that controls it. The new paper identifies a gene (called OsWRI1a, which was previously known only for its role in seed oil biosynthesis). This gene helps rice determine how much to invest above and below ground.
In the growth process, this gene triggers a pathway that promotes tillering, branching that helps determine the number of grain-bearing stalks a rice plant produces. In the root, it interferes with the biological mechanism that normally slows down the hormone that pushes the roots forward. The end result is a plant that does not ring alarm bells when faced with a nitrogen deficiency. Instead of allocating extra energy to the roots and starving the shoots, it keeps growth evenly balanced.
What makes this result immediately useful is that there is already a version of this gene in existing rice varieties. Researchers examined more than 3,000 cultivated cultivars and found that many indica strains carried a naturally stronger version of the japonica cultivars. A slight difference in the ‘biological transformation’ of the gene helps create a stronger version. The researchers transferred the stronger version to the japonica variety through traditional breeding and tested it across three field experiments in Hainan and Anhui provinces in China. The improved plants maintained a more stable balance between root and shoot growth and achieved higher yields across different nitrogen conditions.
Scientific talk: More about gut microbes linked to good health
There’s an evolutionary angle here too. When the team mapped genetic variants against soil nitrogen content across 42 countries and regions, the stronger indica version appeared more often in low-nitrogen soils. This suggests that local nitrogen conditions may have helped shape where different versions of the gene persisted.
This is an exciting study that could make a meaningful difference in how nitrogen is used. However, no single gene will be able to fix decades of heavy fertilizer use in agriculture. Field performance depends on soil, climate, agricultural practices and many other genes that shape yield, so more testing of this approach is needed. But for India, where indica rice is dominant, the research shows the way because the traits breeders want don’t need to be genetically engineered from other crop plants; they already exist in the rice, and in the field.
Anirban Mahapatra is a scientist and author. His latest book is When Medications Don’t Work. The opinions expressed are personal.
