Agriculture accounts for 70% of the global use of available freshwater. Projections show that demand for water will increase significantly due to climate change, population growth and development of agricultural enterprises globally. There is a need to develop water-use efficient crop cultivars for sustainable agricultural production.Sorghum [Sorghum bicolor (L.) Moench.] is a powerhouse crop in drier regions supporting more than 500 million people. It is a relatively drought-tolerant crop adapted to grow and yield in marginal environments where other dominant crops such as maize and wheat fail to survive. However, the mean yield of sorghum in the semi-arid regions has stagnated around 1.0 ton/ha compared with the global average of 2.5 ton/ ha, mainly due to recurrent droughts and heat stress. Breeding for drought-tolerant cultivars is an economic and sustainable mitigation strategy against the current and projected drought stress. Therefore, the objectives of this review were to document the impact of drought stress and the key mitigation strategies under drought-prone semi-arid sorghum production systems. The first section of the review highlighted the impact of drought and its mitigation strategies emphasizing on the use of droughttolerant cultivars as the best strategy. This is followed by perspectives on aspects of drought-response mechanisms, breeding methods and complementary technologies for drought tolerance. Integration of the conventional and molecular breeding technologies with rapid generation advancement methods could reduce the breeding cycle and increase the efficiency of deploying new varieties. Information presented in this review will guide agronomists and breeders to develop and deploy droughttolerant sorghum cultivars that are adapted to the changing production environments in the semi-arid regions.

Maize (Zea mays L.) grain yield is severely constrained by drought and this study was conducted to assess gains in grain yield and other traits of released maize cultivars. Twenty-three maize cultivars plus a check were evaluated under drought and well-watered conditions at Zaria and Kadawa during 2015/2016 and 2016/2017 dry seasons. The 24 cultivars were evaluated using 6 x 4 lattice design with three replications. Genotypes differed significantly for all measured traits except anthesis-silking interval (ASI), husk cover, and number of ears per plant under drought, and ASI, husk cover, and ear aspect under well-watered conditions. Under drought, grain yield ranged from 2251 kg ha−1 for SAMMAZ 31 to 4938 kg ha−1 for SAMMAZ 19, with a genetic gain of 1.93% yr−1. Under well-watered conditions, grain yield varied from 3082 kg ha−1 for SAMMAZ 37 to 5689 kg ha−1 for SAMMAZ 51, with the same genetic gain found under drought conditions. Grain yield reduction as a result of drought was 28.4% and performance under drought predicted performance under well-watered conditions better than vice versa with regression coefficient value of 0.8. Grain yield had significant correlations with all measured traits under both water conditions, except for husk cover, plant and ear heights under drought. Our data revealed that substantial genetic gains have been made in breeding for high grain yield cultivars under drought and well-watered conditions over a period of 16 years in Nigeria.

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