Increasing Genetic Gains in Maize in Stress-Prone Environments of the Tropics

Abstract

Maize (Zea mays L.) provides food security, income, and livelihoods to millions of smallholders in the developing world. However, maize yields in the tropical rainfed environments, especially in sub-Saharan Africa and South Asia, are affected by an array of abiotic and biotic stresses, thereby limiting national maize yields to 1–3 tons per hectare (t/ha), while the global average is around 5 t/ha. Therefore, developing and deploying high-yielding, climate-resilient maize (with tolerance to drought, heat, waterlogging, and biotic stresses), coupled with climate-smart agricultural practices, are critical for improving maize yields, and reducing the high risk and vulnerability of the maize-growing smallholder farmers in the tropics to the climate variability. CIMMYT (International Maize and Wheat Improvement Center) has been intensively engaged since 1970s in breeding elite tropical maize germplasm with tolerance to important abiotic stresses, especially drought, using managed-stress screening and selection for key secondary traits. This formed the base for successful development, testing, and deployment of CIMMYT-derived abiotic stress-tolerant maize varieties in sub-Saharan Africa, Latin America, and Asia, in partnership with an array of public and private sector institutions. Increasing genetic gains and breeding efficiency, especially in developing elite multiple stress-tolerant maize germplasm, requires: (a) carefully undertaken field-based phenotyping at several relevant sites as well as under technically demanding managed-stress screens; (b) better understanding of the genetic architecture of traits; and (c) utilization of modern breeding tools/strategies, including high-throughput and reasonably precise field-based phenotyping, doubled haploid (DH) technology, molecular marker-assisted breeding, genomic selection, transgenics, breeding information management, and decision-support system. At the same time, it has become imperative to defend the genetic gains from devastating transboundary diseases (e.g., maize lethal necrosis or MLN) and insect-pests (e.g., Fall armyworm). Multi-institutional efforts, especially public–private alliances, are key to ensure that the improved varieties effectively reach the climate change-vulnerable farming communities, and to develop and deploy technologies that can protect the maize crops of the smallholders in the tropics from the emerging biotic threats.