Comparative analysis of differential root system architecture in tetraploid and hexaploid wheat under optimal and limiting Nitrogen condition Nitrogen uptake efficiency in tertraploid and hexaploid wheat

Abstract

N uptake efficiency is an important factor in breeding for N use efficiency. The variation in this trait is influenced by many factors once the plant root comes in contact with the soil. This experiment was conducted to compare root traits and N uptake across hexaploid and tetraploid wheat genotypes across three depth zones (0-30 cm, 30-60 cm and > 60 cm) and two N levels (moderate N: N₅₀ (50 kg ha^-1) and control N: N₁₀₀ (100 kg ha^-1)) using image-based phenotyping and analysis. The response of a species for a trait was dependent on the N level as well as the rooting depth. In general, root length and related traits recorded higher mean value at N₅₀ and a greater variance was observed for most root traits at N₁₀₀. The effect of N level was significant for all the N uptake traits including above ground biomass (AGB), N (%), above ground N (AGN) and Nitrogen uptake efficiency (NUpE). For N uptake efficiency, only the genotype effect was significant. Principal component (PC) analysis classified root length traits and N uptake traits along PC1 at both the N levels. However, distribution of genotypes across the two PCs was different at the two N levels. Hierarchical clustering did not restrict the three species to separate clusters and intermixing of genotypes among clusters was observed at both the N levels Among aestivum lines, WH1022(15), UASBW-13354(6) and RAJ 4248 (12) performed better in terms of N uptake efficiency. Amruth (31), UAS (446) (30) and ECI26374 (22) among durum wheat genotypes and DDK50420, NP200 and DDK50332 among dicoccum genotypes were found to have superior performance for NUpE. The current study delineates the importance of evaluation of roots at different depths instead of whole root systems and use of competitive N levels in NUE research so that the N use efficient varieties can perform equally well in the field at moderate N levels.