QTL Analyses, MAS Results, and Perspectives for Drought-Tolerance Improvement in Tropical Maize

Summary The objective of plant improvement can be defined as the accumulation in a plant genome of the maximumnumber of favorable alleles involved in the expression of target traits. This task can be achieved throughseveral approaches and selection schemes, including phenotypic observations and/or DNA marker technology.The emergence of molecular genetics and associated technologies represents a major new breeding tool; thecurrent challenge is to integrate this tool and the information it generates into breeding schemes to furtherthe development of efficient marker-assisted selection (MAS) strategies. This challenge is addressed in thispaper, which particularly considers plant improvement under limited water conditions. After the presentationof QTL identification for target traits involved in maize drought tolerance and a description of two successfulMAS experiments for both line and population improvement, prospects for plant improvement throughbiotechnology are discussed. modifications in physiologicalpathways. Moreover, the globalimpact of water-limited conditions isnot easy to evaluate, especially whendrought is combined with insect orpathogen attack, or with less thanoptimal soil conditions. Althoughimpressive progress has beenachieved through conventionalbreeding (for review, see Heisey andEdmeades, 1999), the potential forgenetic improvement of maizeproduction under droughtconditions is still large. Suchimprovements under drought shouldbe accelerated, given the rapidincrease in supply of new moleculartools, and the explosion in geneticinformation generated throughgenomic approaches.