Variability of Root and Shoot Traits Under PEG-Induced Drought Stress at an Early Vegetative Growth Stage of Maize

The development of maize varieties with enhanced tolerance to drought stress has become a high-priority goal for maize breeding programs worldwide. In order to assess the variability of root and shoot traits in response to drought at an early vegetative stage, a set of 32 maize single-cross hybrids was grown under polyethylene glycol 8000-induced drought stress and well-watered control treatments. Drought stress significantly reduced hybrid seedling root and shoot lengths (RL and SL) as well as root and shoot fresh weights (RFW and SFW), while an increase in seedling root and shoot dry matter (RDM and SDM) and root fresh weight-to-shoot fresh weight ratio (RFW/SFW) was observed. The high heritability estimates for the four directly and easily measured traits, namely, RL, SL, RFW, and SFW (0.83, 0.83, 0.74, and 0.74, respectively), and medium-to-very-strong positive correlations among these traits under drought conditions indicate their applicability for the assessment of maize drought tolerance at the seedling stage and may represent a practical contribution to maize breeding programs for improved drought tolerance. Among the studied hybrids, hybrids 30, 3, and 23 were characterized by the largest RL under drought conditions and small relative change in RL between control and drought treatments. Hybrid 30 also showed one of the smallest relative reductions in SL, RFW, and SFW between the two treatments, while hybrids 3 and 23 were among those which exhibited the highest relative RL/SL and RFW/SFW increase between the two treatments, which supports their potential as parental lines in drought-tolerant breeding.