Nitrogen fertilizer has an indispensable role in increasing crop yields, but on the other hand, it creates a severe threat to ecosystems. For this reason, breeding new crop varieties with high nitrogen use efficiency (NUE) is a high priority for both agricultural production and environmental protection.

Using a diversified rice population from different regions, the scientists carefully evaluated how various agronomic traits responded to nitrogen in fields with different nitrogen supply conditions. They further performed a genome-wide association study (GWAS), with one very significant GWAS signal identified. The detailed mechanisms of how OsTCP19 works in regulating rice tillering were also characterized.

The researchers found that OsTCP19-H, the high NUE allele, was highly preserved in rice types grown in nitrogen-poor regions, but has been lost in rice types grown in nitrogen-rich regions. They also found that OsTCP19-H is also highly prevalent in wild rice which was grown in natural soil without artificial fertilizer input, and concludes that OsTCP19-H introgression into modern cultivars can improve nitrogen use efficiency 20-30% under conditions of decreased nitrogen supply.

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