As with the on-going global effort to ensure security and drive increased empowerment of rural farmers especially women, key African institutions have teamed up on a project to grow stronger Cassava varieties with the potential to achieve the aforementioned objectives.
It’s a scene that plays out all too often in many countries in Africa: a subsistence farmer – often a woman – decides to grow cassava for much-needed money. She takes cuttings from carefully-selected plants and cultivates them for a year, feeding them with fertiliser if she can afford it, and is rewarded with tall, healthy-looking plants. But when the time comes to harvest the edible roots, she hauls them to the processing plant only to be told they lack sufficient starch content to fetch the price she’d hoped. The price she’s offered doesn’t cover the cost of the fertiliser, let alone her time.
The culprit behind this farmer’s disappointment is likely to be either cassava brown streak virus or cassava mosaic virus, both of which ravage cassava crops in Africa. The viruses are a high-priority target of the NextGen Cassava project because of their devastating impact.
The project is applying genotyping and “big data” analysis to the ancient practice of plant breeding to accelerate development of traits such as virus resistance. Our hope is that improved cassava varieties will not only help farmers to feed themselves and their families, but also to profit from their harvests and thus improve their quality of life.
Cassava was brought from South America to Africa by Portuguese traders in the 16th century, and soon caught on because it thrives in dry conditions and marginal soils where other crops would wither. It grows slowly, and is usually grown not from seed, but from cuttings of existing plants – a fact that has enabled viruses to propagate and spread as people have unwittingly planted diseased cuttings, or even transported them across borders in an effort to improve on local varieties. Cassava’s long lifecycle also proves frustrating for plant breeders, who must wait a year to see a plant’s yields before they begin working on the next generation.
To speed up the process, NextGen is adapting a technique originally invented for breeding dairy cattle: genomic selection. The idea is to analyse DNA markers for large numbers of plants and figure out which traits are associated with which markers. That data is then pooled in a publicly accessible, shared database, so that breeders will be able to genotype a seedling and know what kind of plant it will grow up to be. They can then confidently choose parents likely to yield offspring with a combination of desirable traits, such as resistance to viruses, drought tolerance, high starch yield or better nutritional value. We hope genomic selection will make cassava breeding twice as fast.
Given that cassava lacks the resources devoted to western staples such as corn and wheat, the success of this effort depends on our working together to maximise our efforts. For that reason, NextGen Cassava involves multiple US-based institutions as well as the National Crops Resources Research Institute in Uganda, the National Root Crops Research Institute and the International Institute of Tropical Agriculture, both in Nigeria. Pooling our data will create a useful source of information that anyone can use in their own cassava improvement project.
Cassava is a staple for millions of people in sub-Saharan Africa, and improving its reliability and yield will undoubtedly increase food security. But cassava’s potential is broader than that. The women who grow most of Africa’s cassava could use profits from the crop to improve their lives and those of their families. If varieties can be developed that are suitable for industrial farming in Africa, whole countries could benefit from the trade in cassava flour, cassava bio-fuels and cassava starch. Thailand and other Asian countries have already shown that cassava can be a profitable export crop; we believe NextGen will provide the knowledge basis to develop varieties that will make such profit opportunities available for Africa as well.
We are now in the third year of our five-year pilot project. We have had our first breeding cycle, although we won’t know the results until later this year. Collecting the data needed for genomic selection and doubling the pace of their breeding efforts has been a tremendous feat for our African partners, and managing and crunching the data presents challenges of its own. If we can prove the feasibility of our approach during this pilot phase, we hope other cassava-breeding programmes will be persuaded to adopt the genomic selection approach and contribute to our database. Genomic data and knowledge sharing may prove key to unlocking cassava’s true potential in Africa.
Jean-Luc Jannink is a plant research geneticist at the United States Department of Agriculture and an adjunct associate professor at Cornell University.
Culled from Agro Nigeria