Effect of Drought Stress on Physiological Traits of Maize (Zea mays L.) Hybrids

In order to study the effect of drought stress on growth of new hybrids of maize an experiment was carried out at Safi Abad Agricultural Research Center, Dezful, Iran. The experiment was arranged as a split plot in a randomized complete block design with three replications. Treatments consisted of four levels of drought stress (irrigation after 75(±5) (Control), 95(±5) (mild stress), 115(±5) (moderate stress) and 135(±5) mm (severe stress) evaporation from a Class-A pan as main plots and three hybrids of corn (SC704 late-maturing hybrid as local check, Karoon late-maturing hybrid and Mobin medium-maturing hybrid) as subplots. Based on the results, the highest grain yields of 6570 and 6590 kg/ha were obtained under control and mild drought stress conditions, respectively, while the lowest grain yields of 5660 and 4280 kg/ha were obtained under moderate and severe drought stress conditions, respectively. Karoon and SC704 had the highest and the lowest grain yield of 6370 kg/ha and 5160 kg/ha, respectively. Karoon and Mobin hybrids had a greater ability to maintain their yield under drought stress conditions, compared to SC704. Drought led to increase in root depth and Mobin hybrid had the maximum root penetration of 26.6 cm. Drought stress also led to early maturity in the maize hybrids and plants of Karoon hybrid grown under drought were matured 5 days earlier than the non-stressed plants. Increasing the severity of drought led to decrease in dry matter yield by about 56.2 percent compared to control, indicating the key role of water availability in dry matter production. Moderate and severe drought stresses decreased the root dry weight by 4.8 and 9.7 percent, respectively, compared to control. Karoon hybrid had the highest harvest index of nearly 48 percent. Severe drought stress increased the protein content and Mobin hybrid had the highest protein content of 9.34 percent. According to the results, Karoon hybrid was matured 5 days earlier and had greater harvest index and grain yield compared to the control.