Radiation-Use Efficiency, Biomass Production, and Grain Yield in Two Maize Hybrids Differing in Drought Tolerance

Drought-tolerant (DT) maize (Zea mays L.) hybrids have potential to increase yield under drought conditions. However, little information is known about the physiological determinations of yield in DT hybrids. Our objective was to assess radiation-use efficiency (RUE), biomass production, and yield in two hybrids differing in drought tolerance. Field experiments were conducted in 2013 and 2014 with two hybrids, P1151HR (DT hybrid) and 33D49 (conventional hybrid) under well-watered (I-100) and drought (I-50) conditions. I-100 and I-50 refer to 100% and 50% evapotranspiration requirement, respectively. On average, P1151HR yielded 11-27% greater than 33D49 at I-100 and about 40% greater at I-50, At I-100, greater yield in P1151HR was due to greater biomass at physiological maturity (BMpm) resulting from greater post-silking biomass accumulation (BMpost). At I-50, both hybrids had similar BMpm but P1151HR showed a higher harvest index and greater BMpost. RUE differed significantly (P<0.05) between the hybrids at I-100, but not at I-50. At I-100, the RUE values for P1151HR and 33D49 were 4.87 and 4.28gMJ(-1) in 2013, and 3.71 and 3.48gMJ(-1) in 2014. At I-50, the mean RUE was 3.89gMJ(-1) in 2013 and 3.16gMJ(-1) in 2014. Results indicate that BMpost is important for maintaining high yield in DT maize.