Cracking the pigeonpea genetic code to help poor farmers

Thomson Reuters Foundation - Wed, 9 Nov 2011 12:30 GMT
Author: Jerome Bossuet, ICRISAT
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By Jerome Bossuet, ICRISAT

The pigeonpea genome mapping published this month in Nature Biotechnology marks the first subsistence and non-industrial crop to have its genome code cracked.

The breakthrough, announced by a research coalition led by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), will lead to more varieties that are resistant to drought and diseases in coming years. This could boost harvests of the crop and have a major impact on the lives of millions of smallholder farmers in Asia and Africa.

Pigeonpea is vital for poor farmers in the semi-arid tropics of Asia, Africa and South-Central America. It can grow even where water is scarce and the soil poor, needs minimal inputs, and still produces grain that contains more than 20 percent protein.

The “poor person’s meat”, as pigeonpea is known, is an especially important crop for countries grappling with hunger and malnutrition. It provides a well-balanced diet when accompanied with cereals. In India, for example, dry split pigeonpea is often cooked as dal, a traditional dish eaten with rice or bread.

In addition to its protein-packed grains, pigeonpea has many other uses. Its leaves and podded branches make nutritious livestock feed, and the stalks are used as firewood for cooking stoves in many countries. They are also used to weave baskets, construct fences and make thatch roofs.

Besides its value as a multipurpose crop, pigeonpea is unique in its ability to fare well in very harsh environments.  Its drought-tolerance makes it particularly valuable in regions prone to unpredictable rainfall and frequent dry spells.  It is often the only crop that yields grain when other crops like beans and maize have dried up.

But today, the average pigeonpea yield is far lower than it could be - 866 kg/ha in India and 736 kg/ha in Africa, in comparison with the 2,500kg/ha possible in optimum conditions.

ROUTE TO FASTER, CHEAPER BREEDING

Because of its importance for food security in the world’s poorest regions, and the expected expansion of water-scarce regions and declining soil fertility, the pigeonpea genome mapping will have a much-needed impact on yields, environment and livelihoods.

The mapping was the result of a global research partnership - the International Initiative for Pigeonpea Genomics (IIPG) - led by ICRISAT with partners from India, China, the United States and Europe, and support from the CGIAR Generation Challenge Programme.

The pigeonpea’s genome map will transform traditional crop research by showing plant breeders where to start identifying and improving certain traits.

For example, what makes pigeonpea survive during dry periods when other crops fail? How can we make pigeonpea more resistant to the soil-borne disease Fusarium wilt, which is a particular problem in Africa, cutting many farmers’ harvests by up to half? How could pigeonpea fend off the Sterility Mosaic disease virus, or better tolerate waterlogging - two other big challenges?

Pigeonpea productivity has remained stagnant for the last 50 years. Until a few years ago, pigeonpea breeders had just 10 genetic markers to map important traits, making their task impossible. Now the genome map has revealed over 50,000 markers, which will transform their work.

“Having the new pigeonpea sequence as a reference will significantly speed up and reduce the costs of screening for the ‘good genes’ in our pigeonpea seed collections. When it has taken up to 10 years to breed a new variety, with this genome map, we could imagine breeding a new variety in just about three years,” says Rajeev Varshney, lead scientist for the pigeonpea genome sequencing project.

And the costs of developing new improved varieties for farmers will be dramatically reduced, he adds.

Of 48,680 genes identified, a couple of hundred were found specific to the pigeonpea that may shed light on valuable traits, including drought tolerance. 

Climate change has increased the urgency of identifying the genes that will enable pigeonpea to adapt to drier conditions. And the transfer of these genes to close relative legumes such as soybean, cowpea or common bean could soon be a reality.

“With seven billion (people) to feed and rising food insecurity, especially among the dryland smallholder farming population, investing in modern crop improvement technologies for subsistence crops like pigeonpea is crucial,” says William Dar, ICRISAT’s director general.

“Farmers will then have access to improved varieties that can give high yields and meet the future challenges of climate change and scarce natural resources."