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.
ABSTRACT
The presence of genotypic differences in performances under soil water deficit would help plant breeders in initiating successful breeding programs to improve drought tolerance. The objectives of the present study were: (i) to assess the effects of genotype, water stress and their interaction on maize agronomic, physiologic and yield traits and (ii) to identify drought tolerant genotypes for use in future breeding programs. Fifteen commercial hybrids and seven breeding populations were evaluated in the field for two seasons under water stress at flowering (WSF) and grain filling (WSG) compared to well watering (WW). A split plot design with three replications was used. Data analysed across seasons revealed a significant reduction in grain yield/plant (28.69 and 20.26%), grain yield/ha (35.53 and 25.51%), chlorophyll concentration index (30.18 and 44.07%) and 100-kernel weight (6.75 and 12.36%) due to water stress under WSF and WSG, respectively, a significant reduction in ears/plant (11.58%), kernels/row (14.23%), kernels/plant (24.85%) due to water stress under WSF and in upper stem diameter (18.46%) due to water stress under WSG, but a significant increase in days to silking (3.50%), anthesis silking interval (21.17%) and barren stalks (26.18%) due to water stress under WSF. Rank of genotypes differed from one irrigation regime to another for most studied traits. The highest yielding genotypes were Eg-77, P-3444, SC-128 and HT-2066 under WSF and P-3444, SC-128, TWC-324 and SC-166 under WSG, in a descending order. These genotypes could be offered to maize breeding programs for developing drought tolerant inbred and hybrids.