Putative Mechanisms of Drought Tolerance in Maize (Zea mays L.) via Root System Architecture Traits

Abstract

Identifying maize genotypes with favorable root architecture traits for drought tolerance is prerequisite for initiating a successful breeding program for developing high yielding and drought tolerant varieties of maize. The aims of the present study were: (i) to identify drought tolerant genotypes of maize at flowering and grain filling, (ii) to interpret the correlations between the drought tolerance and root architecture traits and (iii) to identify the putative mechanisms of drought tolerance via root system traits. An experiment was carried out in two years using a split plot design with three replications. The main plots were assigned to three water stress levels, namely: well watering (WW), water stress at flowering (WSF) and water stress at grain filling (WSG), and sub-plots to 22 maize cultivars and populations. Drought tolerance index (DTI) had strong and positive associations with crown root length (CRL), root circumference (RC) and root dry weight (DRW) under both WSF and WSG, a negative correlation with brace root whorls (BW), and positive correlations with crown root number (CN) under WSF and brace root branching (BB) and crown root branching (CB) under WSG. These root traits are therefore considered as putative mechanisms of drought tolerance. The cultivars Pioneer-3444, SC-128, Egaseed-77, SC-10 and TWC-324 showed the most drought tolerant and the highest yielding in a descending order; each had a number of such drought tolerance mechanisms. Further investigation should be conducted to determine the underlying root mechanisms contributing to the selection of water-efficient hybrids of maize.