Unravelling Drought Stress Responses in Corn during Early Vegetative Growth Stages.

Corn (Zea mays L.) production worldwide is often challenged various biotic and abiotic pressures and lately drought has drastically impacted on global production levels. Corn is grown on about 30% of U.S. cropland although being highly productive zone, but a significant portion of the corn in the US Midsouth region regularly experiences drought stress during the growing season. Two experiments were conducted using six commercially-grown corn hybrids, P1498, DKC 65-81, N59B-3111A, P1319, DKC 66-97, and N61X-3110, with varied tolerance using mini-hoop houses (Expt. 1) and sunlit controlled environments (Expt. 2) and during early juvenile phases of growth. In Exp. 1, three soil moisture regimes, 100, 66, and 33% field capacity, were imposed soon after emergence and continued for 15 DAS. In Exp. 2, two irrigation treatments, well-watered and water withheld from 10 days after sowing and continued for 15 days. In the both the experiments, root and shoot parameters were estimated at the final harvest. A cumulative drought response index (CDRI) was developed by summing individual response indices for each parameter and was used to classify hybrids as drought tolerant and drought sensitive in both the experiments. The combined drought stress response indices categorized the test hybrids into three classes with CDRI values ranging from 44.40 to 47.46; sensitive – N59-B-311A and DKC6697, moderately sensitive – P1319, and tolerant – DKC6581, N61X-3100, and P1498. The drought tolerant corn hybrids showed greater leaf area, physiological efficiency, and root growth such as total root length, root surface area, root volume, and number of crossings and forks under water limited conditions resulting higher biomass. Further studies are needed to screen large number of land races and corn hybrids to have broader implications for breeding drought tolerant corn genotypes and to help corn producers select hybrids for a niche environment.