Abstract
Climate change is expected to aggravate the effects of drought, heat and combined drought and heat stresses. An important step in developing ‘climate smart’ maize varieties is to identify germplasm with good levels of tolerance to the abiotic stresses. The primary objective of this study was to identify landraces with combined high yield potential and desirable secondary traits under drought, heat and combined drought and heat stresses. Thirty-three landraces from Burkina Faso (6), Ghana (6) and Togo (21), and three drought-tolerant populations/varieties from the Maize Improvement Program at the International Institute of Tropical Agriculture were evaluated under three conditions, namely managed drought stress, heat stress and combined drought and heat stress, with optimal growing conditions as control, for two years. The phenotypic and genetic correlations between grain yield of the different treatments were very weak, suggesting the presence of independent genetic control of yield to these stresses. However, grain yield under heat and combined drought and heat stresses were highly and positively correlated, indicating that heat-tolerant genotypes would most likely tolerate combined drought and stress. Yield reduction averaged 46% under managed drought stress, 55% under heat stress, and 66% under combined drought and heat stress, which reflected hypo-additive effect of drought and heat stress on grain yield of the maize accessions. Accession GH-3505 was highly tolerant to drought, while GH-4859 and TZm-1353 were tolerant to the three stresses. These landrace accessions can be invaluable sources of genes/alleles for breeding for adaptation of maize to climate change.
Highlights
Climate change is predicted to increase global temperatures and reduce rainfall patterns, with adverse effects, on the critical stages of plant growth and development, resulting in yield losses
The peak temperature occurred in April (Figure 1), which coincided with the flowering and grain filling stages
Accession GH-3505 was highly tolerant to drought stress (DS) while GH-4859 and TZm-1353 combined desirable secondary traits with good levels of tolerance to all the stresses
Summary
Climate change is predicted to increase global temperatures and reduce rainfall patterns, with adverse effects, on the critical stages of plant growth and development, resulting in yield losses. Rainfall under future climate change scenarios in SSA will either occur late or stop earlier than usual [1], while temperatures in large areas have already exceeded the threshold for maize growth and productivity [2,3]. Plants 2019, 8, 518 stages of maize causes delayed silking, increased anthesis-silking interval, and reduced kernel set [5], resulting in grain yield (GY) losses above 50% [6,7]. DS at a few days before anthesis to the beginning of grain-filling period reduced GY of maize by as much as 90% [8]
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