Unveiling the role of root functional traits in enhancing nitrogen use efficiency in wheat under nitrogen deficiency

Genetic variation in plant functional traits has been recognized as a potential avenue for enhancing nitrogen use efficiency (NUE) in wheat, which is a cost-effective strategy for reducing environmental burden of excessive N fertilizer application. In this study, a total of 126 diverse wheat genotypes originating from 16 countries were cultivated in pots supplied with a low N level at 10 mg kg^- 1 to explore the functional traits determining NUE and their responses to N limitation.

Under low N condition, significant genetic variations were observed in root morphological traits, photosynthesis capability and NUE among the wheat genotypes. The ranges of NUE and physiological NUE across 126 genotypes were 0.39-1.41 g mg^- 1 and 0.39-1.26 g mg^- 1, respectively. Multivariate analysis revealed the examined root morphological traits were closely associated with plant N content, NUE and biomass accumulation under low N condition. Specially, roots with high root mass density (RMD) were beneficial to improve NUE, while high specific root length (SRL) and specific root surface area (SRA) were positively correlated with plant N concentration in response to N limitation. In contrast, photosynthesis traits exerted little effect on NUE in wheat at early growth stage under low N condition.

Root morphological traits were superior to photosynthesis capacity in mediating wheat response to low N condition. Notably, RMD holds promise for application in breeding programs aimed at improving NUE in wheat.