Taking stock of genetic gains
in tropical maize breeding
programs
CIMMYT has been monitoring the genetic gains in 11 maize breeding pipelines across the tropics. These pipelines already hold the maize for the near future, including lines that are not only higher-yielding, but also climate-resilient, and resistant to major diseases and pests.
A third of the world’s land that is planted to maize is in the tropics, especially in the low- and middle-income countries. Over the past 25 years, maize production in these countries has nearly doubled. This is due as much to bringing more land under cultivation as it is to developing and deploying new, higher-yielding maize. Yet, it is no longer feasible to keep expanding the amount of land devoted to maize, and the focus needs to be on improving productivity.
Breeding for higher yield in stress-prone tropical environments means developing improved varieties that can adapt to the changing climate, including drought, heat, diseases, and insect pests.
In the tropics, maize breeding relies largely on partnerships between CGIAR, the national agricultural research systems (NARS) and the private sector. The improved maize germplasm that these collaborative regional maize breeding networks develop and release as new varieties and hybrids over the next few years are already in the breeding pipeline. At the same time, it is important to monitor the progress being made by the breeding programs, by estimating the genetic gains for grain yield and adaptation to climate change.
A recent global study examined genetic trends in 11 of the tropical maize breeding programs implemented by CIMMYT in collaboration with partners in sub-Saharan Africa, South Asia, and Latin America. The study, published in 2022 in Scientific Reports, analyzed data from 4,152 advanced breeding trials in 28 countries from 2010 to 2020. The results are encouraging. Genetic trends for increased grain yield per hectare per year reached up to 138 kg per hectare per year in Eastern and Southern Africa, 118 kg per hectare per year in South Asia, and 143 kg per hectare per year in Latin America.
To put these numbers in perspective, from 1973 to 2012, genetic gains in the tropics were more modest, boosting maize yields by just 62 kg per hectare annually, an increase of just over 1% a year.
“Previously, breeding programs measured success by the number of varieties they released,” explains B. M. Prasanna, director of CIMMYT’s Global Maize Program. “Of course, we would like to see new varieties being released and made available to the smallholders, but only if they out-perform the older varieties. We especially need to track the potential of the new maize germplasm developed by breeding programs to not only increase yields, but also to provide improved yield stability, especially through adaptation to warmer, drier environments in the tropics.” explains B. M. Prasanna.
Besides drought tolerance, CIMMYT has also been breeding for heat tolerance in South Asia since 2012, together with partners. Substantial progress is being made in developing improved maize germplasm with heat tolerance, incorporating resistance to major diseases. CIMMYT is also working closely with some of the national partners in sub-Saharan Africa (e.g., NARO in Uganda) for monitoring and increasing genetic gains in its maize breeding programs.
Modern tools and approaches, including doubled haploidy, three-season nurseries, molecular marker-assisted breeding, and rapid-cycle genomic selection, are now making maize breeding faster and more efficient. This is important as the genetic gains need to further increase to meet the present and future needs.
Finally, while genetic gains in breeding programs are being significantly improved, it is equally important to ensure that the seed of these improved varieties is delivered to smallholder farmers, with the help of stronger seed systems and extension programs.
KALRO-Kiboko Research Center in Kenya, a major hub for CIMMYT-NARES collaborative maize breeding in Eastern Africa. ©CIMMYT.
B. M. Prasanna
CIMMYT’s plant breeders evaluating wheat lines in Metepec, State of Mexico, Mexico. ©CIMMYT.
CIMMYT has been monitoring the genetic gains in 11 maize breeding pipelines across the tropics.
A recent global study examined genetic trends in 11 of the tropical maize breeding programs implemented by CIMMYT in collaboration with partners in sub-Saharan Africa, South Asia, and Latin America.
