Enhancing Genetic Gains in Maize Under Increasing Abiotic and Biotic Stresses in the Tropics: Are We Making Significant Progress?

Maize is largely grown as a rainfed crop in the tropics, especially in sub-Saharan Africa (SSA) and South Asia, and is particularly vulnerable to several abiotic and biotic stresses. Over the last decade, significant strides have been made in developing and deploying drought-tolerant (DT) maize varieties in 13 countries in SSA. Over 60,000 tons of certified DT maize seed was produced and commercialized by seed companies in Africa, benefiting an estimated 40 million people. An era study conducted recently using CIMMYT-derived maize hybrids (from 2000 to 2010) in southern Africa revealed that genetic gain under optimal conditions, managed/random drought, low N, and maize streak virus (MSV) are comparable with genetic gains in maize yields in other regions of the world, but the progress is still far from optimal, especially under drought and low N. The problem is exacerbated by the emergence and rapid spread of the devastating maize lethal necrosis (MLN) disease in eastern Africa. Intensive efforts are being made to develop and deploy MLN-tolerant/resistant improved maize hybrids with other relevant adaptive traits. Similar situation prevails in South Asia where the rainfed maize yields are severely affected by abiotic and biotic stresses, compounded by the changing climates. The Heat Tolerant Maize for Asia (HTMA) Project (initiated in 2012) enabled establishing a heat stress phenotyping and collaborative multi-location testing network across South Asia. Under HTMA, several highly competitive heat-tolerant maize hybrids have been developed; 24 such hybrids have been licensed to public and private sector partners in four target countries during 2015-2016, and several are in pipeline for release and deployment. Public-private partnerships are key for scaling-up and accelerated deployment of the new climate-resilient hybrids and to significantly improve rainfed maize productivity in South Asia.