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!



Sep 202012

Getting to the core of a world-favourite dessert by unravelling banana’s origin and genealogy

GCP has enabled us to lay a credible foundation, which gave us a leg-up in the intense competition that typifies the genome sequencing arena” – Angélique D’Hont, CIRAD researcher

‘A’ is also for Angélique, as you will see once you read on…

An ‘A’ to our banana team for ushering in a new era in banana genetics. But let soup precede dessert, and don’t let this worry you: stay with us because we’re still very much on the topic and focused on bananas, which offer the whole range from soup and starters, to main course and dessert, plus everything else in between, being central for the food security of more than 400 million people in the tropics: around a third each is produced in Africa, Asia-Pacific and Latin America, and the Caribbean. About 87  percent of all the bananas produced worldwide are grown by small-scale farmers.

Moving back then to soup for starters, we’re serving up our own unique blend of alphanumeric banana ‘soup’, spiced with ABCs, a pinch of 123s, plus a dash of alpha and omega. Curious about the ABCs? Look no further:‘C’ for getting to the core of ‘B’ for bananas, and an ‘A’ score for our ace genomics team that did it.

Read how GCP seeded … and succeeded, in helping open a new era in banana genetics. An achievement by itself, and an important milestone on the road to unlocking genetic diversity for the resource-poor, which is GCP’s raison d’être.

So get your travelling gear please, for time travel with a ‘midspace checkpoint’ in Malaysia.

We start in 2004, when GCP commissioned a survey of diversity with microsatellites (or SSRs, simple sequence repeats) for all mandate food crops in the CGIAR crop research Centres. The objective of that study was to make new genetic diversity from genebank accessions available to breeders.

The endpoint is opening new research avenues to incorporate genes for disease resistance, with the added bonus of an article published in Nature online on July 11 2012, entitled The banana (Musa acuminata) genome and the evolution of monocotyledonous plants.

It may not be quite as easy as the ABC and 123 that The Jacksons promise in song, but we promise you that the science is just as exciting, with practical implications for breeding hardy disease-resistant bananas. Onwards then to the first leg of this three-step journey!

(Prefer a shorter version of this story in pictures? We’ve got it! Choose your medium between Flickr and Facebook)

1) Let’s go Greek: the alpha and omega of it

Rewinding to the beginning

The proof of the pudding is in the eating: we imagine that Jean Christophe Glaszmann just has to be saying “Yummy!” as he samples this banana.

Start point, 2004: “At that time, several research groups had developed SSR markers for bananas, but there was no coordination and only sketchy germplasm studies,” recalls Jean Christophe Glaszmann (pictured), then the leader of what was GCP’s Subprogramme 1 (SP1) on Genetic Diversity on a joint appointment with CIRAD. He stepped down as SP1 Leader in March 2010, and is currently the Director of a multi-institutional research unit Genetic improvement and adaptation of Mediterranean and tropical plants (AGAP, by its French acronym) at France’s Centre de ccoopération internationale en recherche agronomique pour le développement (CIRAD) in Montpellier.

Jean Christophe continues, “The reference studies had been conducted with RFLP* markers, a very useful tool but far too cumbersome for undertaking large surveys. We mobilised Bioversity International, CIRAD and the International Institute of Tropical Agriculture for the project. The process took time, but delivered critical products.[*RFLP stands for restriction fragmented length polymorphism]

Fastforward to 2012, and gets just a little geeky…

Eight years down the road in 2012, the list of achievements is impressive, as evidenced by a suite of published papers which provide the details of the analysis of SSR diversity and describe how the data enabled the researchers to unravel the origin and genealogy of the most important dessert bananas. The origin of the predominant variety – Cavendish – suggested by the markers, involves two rounds of spontaneous hybridisation between three markedly differentiated subspecies. This scheme has been marvellously corroborated by linguistic patterns found in banana variety names as revealed in a paper published in 2011 in the proceedings of USA’s National Academy of Sciences.

But what else happened in between the start- and end-point? We now get to the really ‘sweet’ part of this bonanza for banana breeding!

It is now possible to conduct research to identify and incorporate genes for disease resistance within fertile populations that are close to the early progenitors, and then inter-cross them to re-establish sterility and obtain vigorous, disease-resistant and seedless progenies.

 2) Of bits, bananas, breeding and breadcrumbs

Threading all these bits together for breeding better bananas is akin to following a trail of breadcrumbs, in which GCP played an important facilitating role: where in the germplasm to undertake genetic recombination is one key; and then, how to expedite incorporation of disease resistance and how to control sterility – so as to first suppress it, then re-establish it – is another set of keys that are necessary for proficient breeding.

Hei Leung in the lab at IRRI.

In 2005, Hei Leung (pictured), then Leader of GCP’s Subprogramme 2 on Comparative Genomics (until June 2007) on a dual appointment with the International Rice Research Institute (IRRI), recognised that with GCP’s main focus being drought tolerance in crops, Musa (the banana and plantain botanical genus) was somewhat on the fringe. However, it was still important that GCP support the emergence of banana genomics.

Hei is currently Programme Leader of Genetic Diversity and Gene Discovery at IRRI. He remembers, “We had a highly motivated group of researchers willing to devote their efforts to Musa. Nicolas Roux at Bioversity was a passionate advocate for the partnership. The GCP community could offer a framework for novel interactions among banana-related actors and players working on other crops, such as rice. The team led by Takuji Sasaki of Japan’s National Institute of Agrobiological Science, which had vast experience in rice genome sequencing, added the scientific power. So, living up to its name as a Challenge Programme, GCP decided to take the gamble on banana genomics and help it fly.”

Angélique D’Hont, CIRAD researcher and lead author of the article published in ‘Nature’.

Through several projects, GCP helped consolidate Musa genomic resources, contributed to the establishment of medium-throughput DArT markers as well as the construction of the first saturated genetic map. Additional contributions included the first round of sequencing of large chromosome segments (BAC clones) and its comparison with the rice sequence and a detailed analysis of resistance gene analogues. All these findings have now been published in peer-reviewed journals. And while publication takes time, it still remains a high-premium benchmark for quality and validation of results, and for efficient sharing of information. It reinforces the value of collaboration, builds capacity and gives visibility to all partners, thereby providing potential new avenues for funding.

Such was the case with bananas: using a collaborative partnership framework established with the Global Musa Genomics Consortium, animated by Nicolas Roux and now chaired by Chris Town, the community developed a case for sequencing the genome. With the mentorship of Francis Quétier, contacts were made with various major players in genomics, which in the end formalised a project between France’s CIRAD and CEA–Genoscope, funded by the Agence Nationale de la Recherche and led by Angélique D’Hont (pictured) and Patrick Wincker.

GCP contributed DArT analysis for anchoring the sequence to the genetic map. But, as stressed by Angélique, CIRAD researcher and lead author of the Nature paper: “Above all, GCP has enabled us to lay a credible foundation, which gave us a leg-up in the intense competition that typifies the genome sequencing arena. We were delighted that France rolled the dice in our favour by funding this work.”

3) Musa musings on the road to and from Malaysia checkpoint

Three years down the road, the team published a description of the genome of a wild banana from Malaysia.

Jean Christophe communes with a Musa plant, perhaps musing “What’s your family history and when will you be fully grown?”

Let’s drill down to some technical facts and figures here: the Musa genome has some 520 million nucleotides distributed across 11 chromosomes, revealing traces of past duplications and bearing some 36,000 genes. While most genes derived from duplication tend to lose their function, some develop novel functions that are essential for evolution; bananas seem to have an outstanding range of transcription factors that could be involved in fruit maturity.

And while the road ahead remains long, we now have a good understanding of banana’s genetic diversity, we have genomic templates for functional studies (a whole-gene repertoire) as well as for structural studies (the chromosome arrangement in one subspecies) aimed at unraveling the genomic translocations that could control sterility in the species complex.

It is now possible to conduct research to identify and incorporate genes for disease resistance within fertile populations that are close to the early progenitors, and then inter-cross them to re-establish sterility and obtain vigorous, disease-resistant and seedless progenies.

This is undoubtedly an inspiring challenge towards unlocking the genetic diversity in this crop, which is central to food security for more than 400 million people in the tropics.



Jun 262012

It’s all about water and weakness  or strength. The Greek legend has it that Achilles was dipped into River Styx by his mother, Thetis, in order to make him invulnerable. His heel wasn’t covered by the water and he later died of the wound from an arrow that struck his heel.

In our times, this analogy can be applied to chickpeas, where this streetwise tough customer in the crop kingdom that thrives on the most rugged terrains is hamstrung if there is no rain at the critical grain-filling period – its sole Achilles’ heel, when it cannot take the searing heat in the drylands it otherwise thrives in.

But before you read on about the latter-day borrowing of this ancient legend, and science’s quest to heal the hit from heat and to cure the crop’s fatal flaw on water, first, an important aside…

Who’s now calling the shots in chickpea research?

Molecular breeding in Phase I was led by ICRISAT, with country partners in a supporting role. In Phase II, activities are being led by country partners, which also assures sustainability and continuity of the work. ICRISAT is now in a facilitating role, providing training and data, while the research work is now in the hands of country partners.” – Pooran Gaur, Principal Scientist: Chickpea Breeding,  ICRISAT.

The facts
Chickpeas are an ancient crop that was first domesticated in central and western Asia. Today, this crop is cultivated in 40 countries and is second only to common beans as the food legume most widely grown by smallholders. The two main types of chickpeas – desi and kabuli – are valuable for both subsistence and cash.

Even for the hardy, times are tough
“Chickpeas are well-known to be drought-tolerant,” says Rajeev K Varshney, Principal Investigator of the project to improve chickpeas work in the Tropical Legumes I Project (TLI). He explains, “The plants are very efficient in using water and possess roots that seek out residual moisture in deeper soil layers.” However, he points out that, with changing climatic conditions, especially in drier areas, terminal drought – when rain does not fall during grain-filling – is the crop’s Achilles’ heel, and principal production constraint.

“Chickpeas are such tough plants that, even for conditions of terminal drought, yields can be increased by improving root characteristics and water-use efficiency,” says Rajeev. The research team has identified several lines with superior traits such as drought tolerance, after screening a set of 300 diverse lines selected based on molecular diversity of large germplasm collections.

VIDEO CLIP: Recipe for chickpea success

Enhancing the genetic makeup to beat the heat
The team went on to develop genomic resources such as molecular markers. With these markers, the team developed a high-density genetic map, and identified a genomic region containing several quantitative trait loci (QTLs), conferring drought tolerance. “QTLs help pinpoint, more specifically, the location of genes that govern particular traits like root length” explains Rajeev.

Longer roots will naturally give the plants a deeper reach into the water table. Root length is the difference between survival and perishing, which is why trees will be left standing on a landscape otherwise laid bare by prolonged drought.

Q for ‘quick’: QTLs speed things along from lab to field, and running with the winners
The discovery of QTLs makes identifying tolerant plants not only easier, but also cheaper and faster. “This means that better-adapted varieties will reach farmers faster, improving food security,” says Rajeev.

Pooran Gaur, GCP’s Product Delivery Coordinator for chickpeas, Principal Scientist for Chickpea Breeding at ICRISAT, and an important collaborator on the TLI project, adds, “We began marker-assisted selection backcrossing (MABC) in Phase I. By 2011, lines were already being evaluated in Ethiopia, India and Kenya. We are now at the stage of singling out the most promising lines.”

Putting chickpeas to the test: Rajeev Varshney (left) and Pooran Gaur (right) inspecting a chickpea field trial.

What was achieved in Phase I, and what outcomes are expected?
Phase I run from mid-2007 to mid-2010, during which time 10 superior lines for improved drought tolerance and insect resistance were identified for Ethiopia, Kenya and India. As well, a total of 1,600 SSR markers and 768 SNPs on GoldenGate assays were developed, along with an expanded DArT array with more than 15,000 features. A high-density reference genetic map and two intraspecific genetic maps were developed.

“We now have materials from marker-assisted backcrossing by using the genomic resources we produced in Phase I. These materials were sent to partners last year [2011]. And because in most cases we have the same people working in TLI as in TLII, this material is being simultaneously evaluated across six to seven locations by all TLI and TLII partners,” says Pooran.

“Preliminary analysis of data is quite encouraging and it seems that we will have drought-tolerant lines soon,” adds Rajeev.

Future work, and who’s now calling the shots in the field
In Phase II, 1,500 SNPs on cost-effective KASPar assays have been developed that have been useful to develop a denser genetic map. In collaboration with University of California–Davis (USA) and the National Institute of Plant Genome Research (India), a physical map has been developed that will help to isolate the genes underlying the QTL region for drought tolerance. A novel molecular breeding approach called marker-assisted recurrent selection (MARS) has been adopted. Over the remaining two years of Phase II, the chickpea work will focus on developing chickpea populations with superior genotypes for drought tolerance through MABC and MARS.

Pooran adds, “Molecular breeding in Phase I was led by ICRISAT, with country partners in a supporting role. In Phase II, activities are being led by country partners, which also assures sustainability and continuity of the work. ICRISAT is now in a facilitating role, providing training and data, while the MABC and MARS aspects are both in the hands of country partners.”

“Another important activity in Phase II is development of multi-parents advanced generation intercross (MAGIC) population that will help generation of genetic populations with enhanced genetic diversity,” says Rajeev.

The chickpea work is led by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), working with partners at the Ethiopian Institute of Agricultural Research, Egerton University in Kenya, and the Indian Agricultural Research Institute. Additional collaborators in Phase I included the University of California–Davis (USA), the National Center for Genome Resources (USA) and DArT P/L (Australia).

For more information on the overall work in chickpeas, please contact Rajeev K Varshney, Principal Investigator of the chickpea work.

Video: Featuring Rajeev and partners Fikre Asnake (Ethiopia) and Paul Kimurto (Kenya)

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