Integration of Conventional Breeding and Molecular Tools for Drought Tolerance in Maize: Review

Maize is an important staple crop for food, feed and industry globally. Despite the importance of maize as a principal food crop in developing country, drought is a major constraint that affects maize production, particularly in Sub-Saharan Africa where maize is grown under rainfed condition. Plant breeder has been striving to improve and develop drought tolerance crops. Nevertheless, these efforts still cannot meet the demand of food security due to fast population growth and climatic change. Secondary traits with associated to grain yield, advanced phenotyping, marker assisted selection/QTL, genomic wide association study and genomic selection methods are more expected to help for improvement of drought tolerance in maize. This article discussed the most secondary traits used for selection, plant physiological traits and crossing among drought tolerance elite lines and evaluation their segregants as well as hybrids performance under stress and optimum conditions. Emphasis also given to molecular dissection of drought tolerance complex trats using GWAS and /or gene discovery at hotspot regions for secondary traits, marker-assisted backcrossing and genome selection have been highlighted for increasing genetic gain in grain yield and predicating the breeding value for selection. Thus, further improvement is essential integration of conventional breeding and genomic tools for development of resilience maize varieties for drought tolerance in maize.