A catalytic gene to cut a third of fertilizer use

Published at 12:52 pm January 23rd, 2021

Bangladesh’s success in trebling the production of its staple rice over the past 50 years comes riding on the benefits of the Green Revolution. And the success of the Green Revolution largely relies on chemical fertilizers.

In the process of augmenting Bangladesh’s annual rice output from over 10 million tons in 1971 to 35 million tons now, the country heavily depended on use of chemical fertilizers – urea, in particular.

Scientists and environmentalists say, the intensive application of inorganic nitrogen underlies marked increases in crop production, but imposes detrimental effects on ecosystems –polluting air, water, and fish habitats.  

It is therefore crucial for future sustainable agriculture to improve the nitrogen-use efficiency of crop plants.  

This winter scientists from the Chinese Academy of Sciences (CAS) have found a gene that plays an important role in helping rice adapt to low soil nitrogen. 

They found the gene – OsTCP19-H – highly prevalent in wild rice, grown in natural soil without artificial fertilizer input, and concludes that its introgression into modern cultivars can improve nitrogen use efficiency by 20-30% under conditions of decreased nitrogen supply.

One of the world’s oldest and leading science magazines – Nature – published the CAS scientists’ seminal work titled "Genomic basis of geographic adaptation to soil nitrogen in rice" in its January 6 issue. 

With varietal development infusing the catalyst gene Bangladesh can expect, in the near future, drastic cut on its urea use.

Six state-run urea fertilizer factories in Bangladesh produce less than 0.8 million tons of urea thereby, meeting only 32% of total yearly requirements, said officials at the Bangladesh Chemical Industries Corporation (BCIC). Government has to bear Tk6000 to 9000 crore subsidy on urea as price adjustment for imported urea each year.     

Scientists and officials say, a 30% cut in urea use in growing rice would save huge foreign exchange otherwise spent on meeting urea import bill and also cut the subsidy amount.

Scientists from the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences (CAS), who have identified the gene that plays an important role in helping rice adapt to low soil nitrogen, said breeding new crop varieties with high nitrogen use efficiency (NUE) should be a high priority for both agricultural production and environmental protection.

“Using a panel of diverse rice germplasm collected from different ecogeographical regions, we performed a genome-wide association study (GWAS) on the tillering response to nitrogen—the trait that is most closely correlated with nitrogen-use efficiency in rice—and identified OsTCP19 as a modulator of this tillering response,” reads their paper published in the Nature. 

Notably, OsTCP19-H is also highly prevalent in wild rice--the ancestor of modern cultivated rice--which was grown in natural soil without any applications of chemical fertilizer. As modern high yielding rice varieties are grown with huge urea supply, OsTCP19-H has thus largely been lost. 

Therefore, the scientists concluded, breeding high-yield crops with decreased nitrogen input can be realized by bringing OsTCP19-H back to modern cultivars.

A CAS report quoted the United Kingdom’s John Innes Centre Director, Prof. Dale Sanders, as saying, "This is truly groundbreaking. It will have implications not only for the basic understanding of how plants/rice works, but also has enormous implications for reducing fertilizer use." 

Established in 1949, the Chinese Academy of Sciences is the linchpin of China’s drive to explore and harness high technology and the natural sciences for the benefit of China and the world. Headquartered in Beijing, CAS is home to 80% of China’s large-scale science facilities.  

Why nitrogen is so crucial?

Nitrogen is the most essential nutrient in crop production but also one of the most challenging to work with. The compound is central to global crop production — particularly for major cereals — but while many parts of the world do not have enough to achieve food and nutrition security, in others excess nitrogen from fertilizer leaks into the environment with damaging consequences. 

Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. More than 90% of world industrial production of urea is destined for use as a nitrogen-release fertilizer. 

In plants, nitrogen is used to make amino acids — which make the proteins that construct cells — and is one of the building blocks for DNA. It is also essential for plant growth because it is a major component of chlorophyll, the compound by which plants use sunlight energy to produce sugars from water and carbon dioxide (photosynthesis).

Excess nitrate or that lost through leaching — in which key nutrients are dissolved due to rain or irrigation — can seep into and pollute groundwater streams. Due to limitation of warehouse capacity, lots of urea, both in bulk and in bags, is usually left in open air in Bangladesh resulting in wastage, quality deterioration and air and water pollution.