Morpho-Physiological and Root Architectural Differences Associated with Drought Tolerant Corn Hybrids.

Drought is an important abiotic stress in corn (Zea mays L.) with around 40% of yield loss resulting from suboptimal water availability. The objective of this study was to assess drought tolerance among six commercially available corn hybrids during early growth stages. Three hybrids contain a drought tolerant gene package, advertised to perform better under rain fed conditions (P1498, DKC 65-81, and N59B-3111A).Three other hybrids with similar maturity backgrounds not containing drought tolerance mechanisms were also tested (P1319, DKC 66-97, and N61X-3110). Plants grown in pots outdoors were subjected to three different soil moisture regimes, namely 100%, 66%, and 33% based on field capacity, from 5 to 22 days after planting (DAP). Plant morphology and growth, including several root traits, were measured at the end of the experiment. Gas exchange and fluorescence parameters were recorded at 21 DAP. Most shoot, root, and physiological parameters decreased as drought stress increased, and differed in their response by hybrid. A cumulative drought response index was developed by summing individual drought response indices for each parameter and was used to classify hybrids into groups of tolerance: drought tolerant, moderately drought tolerant, and drought sensitive. Among the six hybrids tested, DKC 66-97 proved to be the most drought tolerant and N61X-3110 was the most drought sensitive. The differences in sensitivity identified among the corn hybrids indicate the possibility of validating hybrids with drought tolerance as well as lead to future research on studying the effects of drought at different growth stages.