Influences of Genotype and Drought at Flowering and Grain Filling on Root Architecture Traits of Zea mays L.

Root architecture traits are important for plant productivity under soil water deficit. The main objective of the present investigation was to assess the effects of deficit irrigation at flowering and grain filling and genotype on maize root traits and grain yield. Twenty two maize genotypes were evaluated in the field under three irrigation regimes; well watering (WW), water stress at flowering (WSF) and at grain filling (WSG) using a split-plot design with three replications. WSF and WSG caused significant reductions of 28.69 and 20.26% in grain yield/plant and 35.53 and 25.51% in grain yield/ha, respectively. WSF caused a significant reduction in four root traits, namely number of aboveground whorls occupied with brace roots (9.31%), number of brace roots (18.27%), number of crown roots (11.50%) and root dry weight (28.31%), but caused a significant increase (elongation) in crown root length (9.90%). On the contrary, WSG caused significant increases in three root traits, namely number of brace roots (10.10%), number of crown roots (14.71%) and root dry weight (11.60%), but caused a significant reduction in branching density of crown roots (10.05%). Significant differences were observed among genotypes for all studied root traits and grain yield across all irrigation regimes. The best genotypes in grain yield under drought at either flowering or grain filling were characterized by more than one desirable root traits. The cultivars P-3444, Egaseed-77 and SC-128 were considered tolerant genotypes to drought at flowering and grain filling and would be recommended to future breeding programs for improving maize drought tolerance.