Physiological Response of a Drought Tolerant Hybrid to Plant Population and Irrigation.

A new generation of drought-tolerant corn hybrids (Zea mays L.) are currently being marketed in Ohio where little research has been conducted. Drought-tolerant hybrids may provide a yield advantage under water limiting conditions, but may incur a yield penalty in the absence of water stress. A field study was conducted in 2013 and 2014 at South Charleston, OH to investigate the physiological response of one drought-tolerant and one non-tolerant hybrid to two plant populations and to irrigation or water exclusion. Measurements included stomatal conductance, chlorophyll fluorescence, light interception, and leaf area index (R2 only). Relative chlorophyll content using SPAD and chlorophyll extractions were conducted at R2. Grain yields were collected at R6. At V17, R2, and R5 in 2013 there were no differences between the hybrids for most measurements. The tolerant hybrid had a greater Fv’/Fm’ ratio and a lower ΔF/Fm’ ratio than the non-tolerant hybrid at V17. At R2, the drought-tolerant hybrid had lower stomatal conductance than the non-tolerant hybrid. Light interception was unchanged by irrigation for the drought-tolerant hybrid at R2, but interception decreased in the non-tolerant hybrid when water was excluded. Leaf area index at R2 was greater for the drought-tolerant hybrid even though leaf number was similar between both hybrids. Relative chlorophyll content decreased for both hybrids as population increased, but was consistently less in the tolerant hybrid. The drought-tolerant hybrid also had less of all pigments per cm² tissue as compared to the non-tolerant hybrid. Plants grown under water exclusion or at the high population produced fewer kernels per plant. A yield penalty was not observed in the tolerant hybrid under irrigation, and a yield advantage was not observed in 2013 under water exclusion. In conclusion, the drought-tolerant hybrid displayed physiological differences from the non-tolerant hybrid and was less affected by water exclusion.