Genotype and Deficit Irrigation Effects on Agronomic, Physiologic, Yield and Root Traits of Maize (Zea mays L.)

The objectives of the present study were: (i) to assess the effects of drought stress at flowering and
grain filling and genotype on maize (Zea mays L.) agronomic, physiologic, yield and root traits of
maize and (ii) to identify high-yielding drought tolerant genotypes with desirable traits for future use in
plant breeding programs. Fifteen commercial hybrids and seven breeding populations were evaluated
in the field for two seasons under water stress at flowering (WSF) and grain filling (WSG) compared to
well watering (WW). A split plot design with three replications was used. Data analyzed across
seasons revealed a significant reduction in grain yield/plant (28.69 and 20.26%), chlorophyll
concentration index (30.18 and 44.07%) and 100-kernel weight (6.75 and 12.36%) due to water stress
under WSF and WSG, respectively, a significant reduction in ears/plant (11.58%), kernels/row
(14.23%), kernels/plant (24.85%), number of 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%) due to water
stress under WSF and in upper stem diameter (18.46%) under WSG, but a significant increase in
days to silking (3.50%), anthesis-silking interval (21.17%), barren stalks (26.18%) and crown root
length (9.90%) due to water stress under WSF. Moreover, WSG caused significant increases in
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%). The best genotypes in
grain yield under drought at either flowering or grain filling were characterized by one or more
desirable root architecture traits. The cultivars P-3444, Egaseed-77 and SC-128 were considered
tolerant to drought at flowering and/or grain filling and would be recommended to future breeding
programs to utilize their desirable root traits and grain yield productivity in improving maize drought
tolerance.