Earth to MARS! On the way to breeding drought-resistant maize for Asia
Maize is rapidly emerging as a key crop in Asian food systems. But in the largely rainfed agriculture practiced in Asia, drought is an important threat to production. So several projects are under way to introduce drought-tolerant maize varieties adapted to the many different growing conditions found in Asia.
Source: GCP Blog
For the past five years, Bindiganavile Vivek and his team at the International Maize and Wheat Improvement Center (CIMMYT), based in Hyderabad, India, have been developing drought-tolerant germplasm for Asia using relatively new molecular-breeding approaches – marker-assisted recurrent selection (MARS), applied in a genomewide selection (GWS) mode.
Driven by consumer demand for drought-tolerant maize varieties in Asia, the researchers in the Asian Maize Drought-Tolerance (AMDROUT) project – one of the projects In CGIAR’s ten-year Generation Challenge Programme (GCP) – have focussed on finding suitable drought-tolerant donors from Africa and Mexico.
Most of these donors are white-seeded, yet in Asia, market and consumer preferences predominantly favour yellow-seeded maize. Moreover, maize varieties are very site-specific and this poses yet another challenge.
Clearly, breeding is needed for any new target environments, all the while also with an eye on pronounced market and consumer preferences.
Stalked by drought, tough to catch, but still the next big thing
Around 80 per cent of the 19 million hectares of maize in South and Southeast Asia is grown under rainfed conditions, and is therefore susceptible to drought, when rains fail. Tackling drought can therefore provide excellent returns to rainfed maize research and development investments. As we shall see later, Vivek and his team have already made significant progress in developing drought-tolerant maize.
But they are after a tough target: drought tolerance is dodgy since it is a highly polygenic trait, making it difficult for plant scientists to pinpoint genes for the trait (see this video with an example from rice in Africa).
In other words, to make a plant drought-tolerant, many genes have to be incorporated into a new variety.
As one would expect, the degree of difficulty is directly proportional to the number of genes involved. In the private-sector seed industry, MARS has been successfully used in achieving rapid progress towards high grain yield under optimal growth conditions. Therefore, a similar approach could be used to speed up the process of introducing drought tolerance into Asian crops – the reason why the technique is now being used by this project.
The rise of maize: the chicken-and-egg sequence
Vivek says that the area used for growing maize in India has expanded rapidly in recent years. In some areas, maize is in fact displacing sorghum and rice. And the maize juggernaut rolls beyond India to South and Southeast Asia. In Vietnam, for example, the government is actively promoting the expansion of maize acreage, again displacing rice. Other countries involved in the push for maize include China, Indonesia and The Philippines.
So what’s driving this shift in cropping to modern drought-tolerant maize? The curious answer to this question lies in food-chain dynamics. According to Vivek, the driver is the dramatic increase in demand for meat – particularly poultry. Some 70 percent of maize produced is going to animal feed, and 70 percent of that is going into the poultry sector alone.
Show and tell: posting and sharing dividends
As GCP approaches its sunset in December 2014, Vivek reports that all the AMDROUT milestones have been achieved. Good progress has been made in developing early-generation yellow drought-tolerant inbred lines. The use of MARS by the team – something of a first in the public sector – has proved to be useful. In addition, regional scientists have benefitted from broad training from experts on breeding trial evaluation and genomic selection (photo-story on continuous capacity-building).
“GCP gave us a good start. We now need to expand and build on this,” says Vivek.
According to Vivek, the AMDROUT project laid the foundation for other CIMMYT projects such as the Affordable, Accessible, Asian Drought-Tolerant Maize project (popularly known as the ‘Triple-A project’) funded by the Syngenta Foundation for Sustainable Agriculture. This project is building on the success of AMDROUT, developing yet more germplasm for drought tolerance, and going further down the road to develop hybrids.
Increasing connections, and further into the future
Partly through GCP’s Integrated Breeding Platform (IBP), another area of success has been in informatics. Several systems such as the Integrated Breeding FieldBook, the database Maize Finder and the International Maize Information System (IMIS) now complement each other, and allow for an integrated data system.
There is now also an International Maize Consortium for Asia (IMIC–Asia), comprising a group of 30 commercial companies – ranging from small to large, local to transnational – and coordinated by CIMMYT.
Through this consortium, CIMMYT is developing maize hybrids for specific environmental conditions, including drought. IMIC–Asia will channel and deploy the germplasms produced by AMDROUT and other projects, with a view to assuring impact in farmers’ fields.
Overall, Vivek’s experience with GCP has been very positive, with the funding allowing him to focus on the agreed milestones, but with adaptations along the way when need arose: Vivek says that GCP was open and flexible regarding necessary mid-course corrections that the team needed to make in their research.
But what next with GCP coming to a close? Outputs from the AMDROUT project will be further refined, tested and deployed through other projects such as Triple A, thus assuring product sustainability and delivery after GCP winds up.