High-yielding nitrate transporter cultivars also mitigate methane and nitrous oxide emissions in paddy.

Development of high yield rice varieties is critical to ensuring global food security. However, the emission of greenhouse gases (GHG) such as Methane (CH) and Nitrous oxide (NO) from paddy fields threatens environmental sustainability. In this study, we selected overexpressed high-affinity nitrate transporters (NRT2.3 along with their partner protein NAR2.1) cultivars, which are effective nitrogen use efficient transgenic lines (Ox2) and (O8). We used high (270 kg N/ha) and low (90 kg N/ha) nitrogen (N) fertilizers in paddy fields to evaluate morphophysiological traits, including GHG emission. We found that Ox2 and O8 reduced CH emissions by 40% and 60%, respectively, compared to their wild type (WT). During growth stages, there was no consistent NO discharge pattern between WT and transgenics (Ox2, O8) in low and high N application. However, total cumulative NO in a cropping season reduced in O8 and increased in Ox2 cultivars, compared to WT. Root aerenchyma formation reduced by 30-60% in transgenic lines. Methanogens like in low and high N were also reduced by up to 50% from rhizosphere of Ox2 and O8. However, the nitrifying bacterial population such as reduced in both transgenics significantly, but and did not show a consistent variation. The high yield of transgenic rice with limited aerenchyma mitigates the discharge of CH and NO by reducing root exudates that provide substrates for GHG. Our results improve understanding for breeders to serve the purpose of sustainable development.