A comparative analysis of root traits in diverse wheat seedlings screened under optimum and low nitrogen stress in hydroponics

Enhancing nitrogen use efficiency (NUE) by improving N uptake through roots can deal with the global issue of high nitrogenous fertilizer consumption in wheat. Low N induces some adaptive changes in root architectural traits to enhance its acquisition. This study aimed to identify genotypes with improved root traits contributing to efficient N uptake. A panel of 201 diverse wheat genotypes were phenotyped for root traits at seedling stage at optimum (7.5 mM) and low (0.01 mM) N in hydroponics. Results showed a large genetic variation in root traits under N deficiency. Significant enhancement in primary root length (PRL), total root length (TRL), total root surface area (TSA), total root volume (RV), total number of root tips, root biomass (RB) and root to shoot ratio (RSR) was observed at low N with a significant reduction in average diameter (AD) and shoot biomass (SB). The principal component analysis (PCA) revealed that PC1 and PC2 together accounted for 65.4% and 71.0% of the variability under optimum and low N respectively. Major contribution towards genetic variability was explained by TRL, TSA, RB and number of root tips under optimum N and TRL, TSA, RB, and RSR under low N. Hence, the traits like TRL, TSA, and RB can be considered while breeding for higher N uptake in wheat. Cluster analysis revealed that cluster I genotypes possessed better root growth whereas cluster III-b exhibited poor root growth under low N. Fifteen genotypes from both clusters were selected using the rank sum method and subjected to field testing to assess yield performance under low N condition. Notably, genotypes like GUTHA, GW 322, HD 2987, NANJING 8611, and HD 2891, which showed robust root growth in hydroponic conditions under N stress, also exhibited good yield in the field. These genotypes can be utilized for cultivation in N deficient soils and as potential donors for enhancing N uptake.