Roots and shoot traits contributing to drought tolerance from germination to maturity stages for bread wheat

Drought is the major bottleneck for food security worldwide. Identifying reliable selection traits that sustain plant growth and productivity under water-deficient conditions is essential for releasing resilient drought tolerant wheat genotypes. Herein, in order to identify the best combination of drought tolerance related-traits, this study was carried out to assess the effect of 21 shoot and 17 root secondary traits on grain yield of 40 bread wheat genotypes from germination to maturity stages under laboratory, greenhouse and field conditions. In this research, germination rate (GR), mean germination time (MGT), roots weight (RW), roots number (RN) and Root : Shoot ratio (R/S) were relevant for discriminating drought tolerant genotypes, expressing negative moderate correlation ( r ~ -0.5) and explaining a significant part of yield variation (8 to 30%). Grain number (GN) was the most important agronomic trait (r ~0.70–0.94) which explained up to 88% of yield variation. This latter effect is reinforced by the indirect effects of productive spikes number (FSN), thousand kernel weight (TKW) and grains number per fertile spike (GNFS). The biomass (BY), ground cover (GC), spike (SL) and pedoncule lengths (PL) were also relevant, especially under severe stress ( r = 0.4–0.6; β = 0.33–0.40); while the canopy temperature depression (CTD) was determinant under moderate stress ( r = -0.45; β = -0.46). Combined selection for these traits will be effective to improve the process of developing high-yielding bread wheat varieties adapted to drought prone areas.