Jun 242014

Triumphs and tragedies, pitfalls and potential of the ‘camel crop’Cassava leaf. Photo: N Palmer/CIAT

We travel through space and time, with a pair of researchers who have a pronounced passion for a plant brought to Africa by seafaring Portuguese traders in the 16th century. Fastforwarding to today, half a millennium later, the plant is widespread and deep inland, and is the staple food for Africa’s most populous nation – Nigeria.

Meet cassava, the survivor. After rice and maize, cassava is the third-largest source of carbohydrate in the tropics. Surviving, nay thriving, in poor soils and shaking off the vagaries of weather – including an exceptionally high threshold for drought – little wonder that cassava, the ‘camel’ of crops is naturally the main staple in Nigeria. And with that, it has propelled Nigeria to the very top of the cassava totem pole as the world’s leading cassava producer, and consumer: most Nigerians eat cassava in one form or another practically every day.

Great, huh? But there’s also a darker side to cassava, as we will soon find out from our two cassava experts. For starters, the undisputed global cassava giant, Nigeria, produces just enough to feed herself. Even if there were a surplus for the external demand, farming families, which make up 70 percent of the Nigerian population, have limited access to these lucrative external markets. Secondly, cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) are deadly in Africa. Plus, cassava is a late bloomer (up to two years growth cycle, typically one year), so breeding and testing improved varieties takes time. Finally, cassava is most definitely not à la mode at all in modern crop breeding: the crop is an unfashionably late entrant into the world of molecular breeding, owing to its complex genetics which denied cassava the molecular tools that open the door to this glamour world of ‘crop supermodels’.

Emmanuel Okogbenin (left) and Chiedozie Egesi (right) in  a cassava field.

Emmanuel Okogbenin (left) and Chiedozie Egesi (right) in a cassava field.

But all is not doom and gloom, which inexorably dissolve in the face of dogged determination. All the above notwithstanding, cassava’s green revolution seems to be decidedly on the way in Nigeria, ably led by born-and-bred sons of the soil: Chiedozie Egesi and Emmanuel Okogbenin (pictured right) are plant breeders and geneticists at the National Root Crops Research Institute (NRCRI). With 36 years’ collective cassava research experience between them, the two men are passionate about getting the best out of Nigeria’s main staple crop, and getting their hands into the sod while about it: “I’m a plant breeder,” says Chiedozie, with pride. “I don’t just work in a laboratory. I am also in the field to experience the realities.”

Hitting two birds with one stone…two stones are even better!
As Principal Investigators (PIs) leading three different projects in the GCP-funded Cassava Research Initiative, Chiedozie and Emmanuel, together with other colleagues from across Africa, form a formidable team. They also share a vision to enable farmers increase cassava production for cash, beyond subsistence. This means ensuring farmers have new varieties of cassava that guarantee high starch-rich yields in the face of evolving diseases and capricious weather.

Chiedozie is one of cassava’s biggest fans. His affection for, and connection to, cassava is almost personal and definitely paternal. He is determined to deploy the best plant-breeding techniques to not only enhance cassava’s commercial value, but to also protect the crop against future disease outbreaks, including ‘defensive‘ breading. But more on that later…

Emmanuel is equally committed to the cassava cause. As part of his brief, Emmanuel liaises with the Nigerian government, to develop for – and promote to – farmers high-starch cassava varieties. This ensures a carefully crafted multi-pronged strategy to revolutionise cassava: NRCRI develops and releases improved varieties, buttressed by financial incentives and marketing opportunities that encourage farmers to grow and sell more cassava, which spurs production, thereby simultaneously boosting food security while also improving livelihoods.

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Standing tall. Disease resistance and high starch and yield aside, farmers also prefer an upright architecture, which not only significantly increases the number of plants per unit, but also favours intercropping, a perennial favourite   for cassava farmers.

Cross-continental crosses and cousins, magic for making time, and clocking a first for cassava

No one has been able to manufacture time yet, so how can breeders get around cassava’s notoriously long breeding cycle? MAS (marker-assisted selection) is crop breeding’s magic key for making time. And just as humans can benefit from healthy donor organ replacement, so too does cassava, with cross-continental cousins donating genes to rescue the cousin in need. Latin American cassava is nutrient-rich, while African cassava is hardier, being more resilient to pests, disease and harsh environments.

Thanks to marker-assisted breeding, CMD resistance from African cassava can now be rapidly ‘injected’ much faster into Latin American cassava for release in Africa. Consequently, in just a three-year span (2010–2012), Chiedozie, Emmanuel, Martin Fregene of the Donald Danforth Plant Science Center (USA) and the NRCRI team, released two new cassava varieties from Latin American genetic backgrounds (CR41-10 and CR36-5). These varieties, developed with GCP funding, are the first molecular-bred cassava ever to be released, meaning they are a momentous milestone in cassava’s belated but steady march towards its own green revolution.

Marker-assisted selection is much cheaper, and more focused.” 

On the cusp of a collaborative cassava revolution: on your marks…
With GCP funding, Chiedozie and Emmanuel have been able to use the latest molecular-breeding techniques to speed up CMD resistance. Using marker-assisted selection (MAS) which is much more efficient, the scientists identified plants combining CMD resistance with desirable genetic traits.

“MAS for CMD resistance from Latin American germplasm is much cheaper, and more focused,” explains Emmanuel. “There is no longer any need to ship in tonnes of plant material to Africa. We can narrow down our search at an early stage by selecting only material that displays markers for the genetic traits we’re looking for.” Using markers, combining traits (known as ‘gene pyramiding’) for CMD resistance is faster and more efficient, as it is difficult to distinguish phenotypes with multiple resistance in the field by just observing with the naked eye. This is what makes marker-assisted breeding so effective and desirable in Africa.

GCP’s mode of doing business coupled with its community spirit has spurred the NRCRI scientists to cast their eyes further out to the wider horizon beyond their own borders.

By collaborating with research centres in other parts of the world, Emmanuel and Chiedozie have made remarkable strides in cassava breeding. According to Emmanuel, “GCP helped us make links with advanced laboratories and service providers like LGC Genomics. The outsourcing of genotyping activities for molecular breeding initiatives is very significant, as it enables us to carry out analyses not otherwise possible.”

We can’t afford to sit idle until it comes – we need to be armed and on the ready.”

‘Defensive’ breeding: partnerships to pre-empt catastrophe and combat disease
Closer home in Africa, as PI of the corollary African breeders community of practice (CoP) project, Emmanuel co-organises regular workshops with plant breeders from a dozen other countries (Côte d’Ivoire, DR Congo, Ethiopia, Ghana, Kenya,  Liberia, Malawi, Mozambique, Sierra Leone, Tanzania, Uganda and South Sudan). These events are an opportunity to share knowledge on molecular breeding and compare notes.

Of the diseases that afflict cassava, CBSD is the most devastating. Mercifully, in Nigeria, the disease is non-existent, but Chiedozie is emphatic that this is by no means cause for complacency. “If CBSD gets to Nigeria, it would be a monumental catastrophe!” he cautions. “We can’t afford to sit idle until it comes – we need to be armed and on the ready.”

Putting words to action, though this work on CBSD resistance is still in its early stages, more than 1,000 cassava genotypes (different genetic combinations) have already have been screened in the course of just one year. Chiedozie hopes that the team will be able to identify key genetic markers, and validate these in field trials in Tanzania, where CBSD is widespread. This East African stopover, Chiedozie emphasises, is a crucial checkpoint in the West African process. So the cassava CoP not only provides moral but also material support.

And Africa is not the limit. GCP-funded work on CMD resistance is more advanced than the CBSD work, though the real breakthrough in CMD only happened recently, on the international arena within which the African breeders now operate. According to Chiedozie, two entire decades of screening cassava genotypes from Latin America yielded no resistance to CMD. The reason for this is that although it is widespread in Africa, CMD is non-existent in Latin America.

Through international collaborative efforts, cassava scientists, led by Martin Fregene (now based in USA), screened plants from Nigeria and discovered markers for the CMD2 gene, indicating resistance to CMD. Once they had found these markers, the scientists were off and away! By taking the best of the Latin American material and crossing it with Nigerian genotypes that have CMD resistance, promising lines were developed from which the Nigerian team produced two new varieties. These varieties, CR41-10 and CR36-5, have already been released to farmers, and that is not all. More varieties bred using these two as parents are in the pipeline.

“GCP funding has given us the opportunity to show that a national organisation can do the job and deliver.” 


Delivery attracts
The success of the CGP-funded cassava research in Nigeria lies in its in-country leadership. Chiedozie, Emmanuel and Martin are native Nigerian scientists and as such are – in many ways – best placed to drive a research collaboration to benefit the country’s farmers and boost food security. “GCP funding has given us the opportunity to show that a national organisation can do the job and deliver,” says Chiedozie.

This proven expertise has helped NRCRI forge other partnerships and attract more financial support, for example from the Bill & Melinda Gates Foundation for a project on genomic selection. GCP support has also bolstered communications with the Nigerian government, which has launched financial instruments, such as a wheat tariff,* to boost cassava production and use.

[Editors note: * wheat tariff: The Nigerian government is trying to reduce wheat import bills and also boost cassava commercialisation by promoting 20 percent wheat substitution in bread-making. Tariffs are being imposed on wheat to dissuade heavy imports and encourage utilisation of high-quality cassava flour for bread.]

“The government feels that to quickly change the fortunes of farmers, cassava is the way to go,” explains Emmanuel. He clarifies, “The tariff from wheat is expected to be ploughed back to support agricultural development – especially the cassava sector – as the government seeks to increase cassava production to support flour mills. Cassava offers a huge opportunity to transform the agricultural economy and stimulate rural development, including rapid creation of employment for youth.”

The Nigerian government is right in step aiding cassava’s march towards the crop’s own green revolution, as is evident in the the Minister of Agriculture’s tweet earlier this year, and in his video interview below. See also related media story, ‘Long wait for cassava bread’.

Clearly, the ‘camel’ crop – once considered an ‘orphan’ in research  –  has travelled as far in science as in geography, and it is a precious asset to deploy for food production in a climate-change-prone world. As Emmanuel observes, cassava’s future can only be brighter!

Slides by Chiedozie and Emmanuel


More links


Mar 042014
‘Made (up) in Ghana’

In the world of crop research as in the fashion industry, there are super-models, mere models, spectators and rank outsiders. Make no bones about it, trusty old cassava (Manihot esculenta) is a crop of very modest beginnings, but now finally strutting the research catwalk alongside the biggest and the best.

Elizabeth Parkes

Elizabeth Parkes

An ancient crop thought to have been first domesticated in Latin America more than 10,000 years ago, it was exported by Portuguese slave traders from Brazil to Africa in the 16th century as a cheap source of carbohydrates. From there, today we travel half a millennium forward in time – and in space, on to Ghana – to catch up with the latest on cassava in the 21st century.

Come on a guided tour with Elizabeth Parkes (pictured), of Ghana’s Crops Research Institute (CRI, of the Council for Scientific and Industrial Research, CSIR), currently on leave of absence at the International Institute of Tropical Agriculture (IITA).

A hard-knock life, but still going strong
In keeping with its humble heritage, cassava is a crop which has long been reputed for being more than a little worn through at the elbows, commonly known as a “poor man’s crop” according to GCP cassava breeder and researcher, Elizabeth Parkes. However, much like a dishevelled duffle coat, what the crop lacks in shimmer and shine, it makes up for in sturdiness and dependability, rising to the occasion time and again by filling a critical gap – that of putting food in bellies – with a readiness and ease that its more sophisticated crop relatives have often struggled to keep up with. Elizabeth explains:  “It has kept people alive over the years.” By the same token, the crop – now one of Africa’s most important staples – is fondly known in Ghana as bankye, meaning a ‘gift from the government’, thanks to its reliability and capacity to meet needs that other crops cannot. There is even a popular song in the country which pays homage to the crop as an indefatigable evergreen, conquering even the most willful and wily of weeds!

However, as cassava experts such as Elizabeth know only too well, behind this well-intentioned lyrical window dressing is the poignant story of a crop badly in need of a pressing pick-me-up. Hardy as it may seem on the surface, cassava is riddled with myriad problems of a political, physiological, environmental and socioeconomic nature, further compounded by the interactions between these. For starters, while it may be a timeless classic and a must-have item at the family table for a good part of Africa, à la mode it is not, or at least not for short-sighted policy-makers looking first and foremost to tighten their purse strings in straitened times, or for quick-fix, rapid-impact,  silver-bullet solutions: “African governments don’t invest many resources in research. Money is so meager, and funds have mostly come from external agencies looking to develop major cereals such as rice. Cassava has been ignored and has suffered a handicap as a result – it’s more or less an orphan crop now,” Elizabeth laments. Besides having to bear witness to their favourite outfit being left on the funding shelf, cassava breeders such as Elizabeth are also faced with a hotchpotch of hurdles in the field: “In addition to factors such as pests and disease, cassava is a long-season and very labour-intensive crop. It can take a whole year before you can expect to reap any rewards, and if you don’t have a strong team who can step in at different points throughout the breeding  process, you can often find unexpected results at the end of it, and then you have to start all over again,” Elizabeth reveals. Robust as it may be, then, cassava is no easy customer in the field: “After making crosses, you don’t have many seeds to move you to the next level, simply because with cassava, you just don’t get the numbers: some are not compatible, some are not flowering; it’s a real bottleneck that needs to be overcome,” she affirms.

No time for skirting the issue
And at the ready to flex their research muscles and rise to these considerable challenges was Elizabeth and her Ghanaian CRI  team, who – with GCP support and in unison with colleagues from across Africa and the wider GCP cassava community – have been working flat out to put cassava firmly back on the research runway.

Thanks to funders such as GCP, who recognised that we couldn’t afford to turn a blind eye to the plight of this struggling crop, cassava has been given a voice…cassava is no longer just a poor man’s staple” 

A cassava farmer in Northern Ghana.

A  cassava farmer in Northern Ghana.

Elizabeth walks us through the team’s game plan: “GCP socioeconomist Glenn Hyman and team undertook a study to identify the best area in Ghana for supporting cassava flowering [Editor’s note: Glenn works at the International Center for Tropical Agriculture, CIAT]. Armed with that information, we have been applying grafting techniques, using hormones to induce flowering in Ghana and beyond.” The initiative is starting to bear fruit: “At the IITA–Nigeria Ubiaja site, for example, flowering is underway at factory-like efficiency – it’s a great asset. The soil has also greatly improved – we haven’t been able to pinpoint the exact cause yet, but what we’ve seen is that all cultivars there will now flower,” she reveals. Elizabeth’s team has been making steady progress in biotechnological techniques such as DNA extraction: thanks to work led by then GCP cassava comrade Martin Fregene (then with the International Center for Tropical Agriculture, CIAT, and now with the Donald Danforth Plant Science Center) and colleagues, focusing on the development of more reliable and robust simple sequence repeat (SSR) markers, Elizabeth was able to carry out genetic diversity diagnosis work on cassava, collecting germplasm from all over Ghana for the global GCP cassava reference set. [Editor’s note: A ‘reference set’ is a sub-sample of existing germplasm collections that facilitates and enables access to existing crop diversity for desired traits, such as drought tolerance or resistance to disease or pests]

Similar work was also conducted in Nigeria and Guatemala. So has this tremendous and tenacious teamwork proved strong enough to drag cassava out of the doldrums? Elizabeth certainly seems to think so: “Thanks to funders such as GCP, who recognised that we couldn’t afford to turn a blind eye to the plight of this struggling crop, cassava has been given a voice. Having worked together to understand the peculiarities of this crop, cassava is no longer just a poor man’s staple: beyond subsistence, it is becoming a crop of high starch quality, and of real use for industry, confectionary and even biofuels,” she enthuses.

Thankfully, it’s a most welcome change of tide that shows no sign of abating any time soon.  Human capacity, Elizabeth says, is going from strength to strength, with three GCP-funded Ghanaian postgraduate students advancing well, two of them working on PhDs in what would normally be considered, according to Elizabeth, a ‘no-go area’ of cassava research – that is, cassava drought tolerance and post-harvest physiological deterioration (PPD), as well as bio-fortification. Efforts by the CRI team have resulted in the release of some 14–15 new drought-tolerant and PPD-resistant varieties in Ghana to date; all are anticipated to have a long shelf-life, and other varieties are also in the pipeline. Biofortified seeds are in the making, with a view to soon mainstream biofortification in the team’s breeding activities. The biofortification work is in collaboration with a sister CGIAR Challenge Programme, HarvestPlus.

The impact of our GCP-supported research on cassava has been remarkable. Above all, it’s been the community spirit which has moved things forward so effectively; in this respect, I think researchers working on other crops might want to borrow a leaf from the cassava book!”

Molecular masterstrokes, a leaf to lend despite cold shoulder, and a ‘challenge crop’ befitting Challenge Programmes
Forthcoming plans for Elizabeth and her cassava companions in Ghana include a GCP Cassava Challenge Initiative project which will seek to unearth new marker populations and materials which are drought-tolerant and resistant to cassava mosaic virus and cassava bacterial blight. The team has successfully introgressed materials from CIAT into their landraces, and the next step will be to gauge how best the new genes will react to these traits of interest. In terms of people power, the CRI biotechnology laboratory built with GCP support – and now a regionally accredited ‘Centre of Excellence’ – is a hive of activity for local and international scientists alike, and is consequently bolstering cassava research efforts in the wider subregion. “The impact of our GCP-supported research on cassava has been remarkable. Above all, it’s been the community spirit which has moved things forward so effectively; in this respect, I think researchers working on other crops might want to borrow a leaf from the cassava book!” Elizabeth ventures.

Reflecting back on the conspicuous cocktail of constraints which mired the crop in the early days of her research career – challenges which often resulted in a cold shoulder from many of her research peers over the years – Elizabeth recalls affectionately: “At first, people didn’t want to work on cassava since it’s truly a challenge crop: the genetics of cassava are really tricky. Colleagues from around the globe often asked me: ‘Why not go for a smooth crop which is friendly and easy?’” Her commitment, however, has been unfaltering throughout: “I’ve stuck with cassava because that’s my destiny! And now I see SNPs being developed, as well as numerous other resources. Once you clean something up it becomes more attractive, and my thanks go out to all those who’ve remained dedicated and helped us to achieve this.”

Thus, dusted down and  ‘marked-up’ with a molecular make-over well underway, all evidence now suggests that this once old-hat subsistence crop is en route to becoming the next season’s big research hit, with shiny new cassava varieties soon to be released at a field station near you! Go, Ghana, go!



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