Apr 042014
 
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Phil Roberts

Phil Roberts

Like its legume relatives, cowpeas belong to a cluster of crops that are still referred to in some spheres of the crop-breeding world as ‘orphan crops’. This, because they have largely been bypassed by the unprecedented advances that have propelled ‘bigger’ crops into the world of molecular breeding, endowed as they are with the genomic resources necessary. But as we shall hear from Phil Roberts (pictured), of the University of California–Riverside, USA, and also the cowpea research leader for the Tropical Legumes I Project (TLI), despite the prefix in the  name, this ‘little kid’ in the ‘breeding block’ called cowpeas is uncowed and unbowed, confidently striding into the world of modern crop breeding, right alongside the ‘big boys’! What more on this new kid on the block of modern molecular breeding? Phil’s at hand to fill us in…

Vigna the VIP that shrinks with the violets
But is no shrinking violet, by any means, as we shall see. Also known  as niébé in francophone Africa, and in USA as black-eyed peas (no relation to the musical group, however, hence no capitals!), this drought-tolerant ancient crop (Vigna unguiculata [L] Walp) originated in West Africa. It is highly efficient in fixing nitrogen in the unforgiving and dry sandy soils of the drier tropics. And that is not all. This modest VIP is not addicted to the limelight and is in fact outright lowly and ultra-social: like their fetching African counterpart in the flower family, the African violet, cowpeas will contentedly thrive under the canopy of others, blooming in the shade and growing alongside various cereal and root crops, without going suicidal for lack of limelight and being in the crowd. With such an easy-going personality, added to their adaptability, cowpeas have sprinted ahead to become the most important grain legume in sub-Saharan Africa for both subsistence and cash. But – as always – there are two sides to every story, and sadly, not all about cowpeas is stellar…

Improved varieties are urgently needed to narrow the gap between actual and potential yields… modern breeding techniques… can play a vital role”

A cowpea experimental plot at IITA.

A cowpea experimental plot at IITA.

What could be, and what molecular breeding has to do with it
Yields are low, only reaching a mere 10 to 30 percent of their potential, primarily because of insect- and disease-attack, sometimes further compounded by chronic drought in the desiccated drylands cowpeas generally call home. “Improved varieties are urgently needed to narrow the gap between actual and potential yields,” says Phil. The cowpea project he leads in TLI is implemented through GCP’s Legume Research Initiative. Phil adds, “Such varieties are particularly valuable on small farms, where costly agricultural inputs are not an option. Modern breeding techniques, resulting from the genomics revolution, can play a vital role in improving cowpea materials.”

He and his research team are therefore developing genomic resources that country-based breeding programmes can use. Target-country partners are Institut de l’Environnement et de Recherches Agricoles (INERA) in Burkina Faso; Universidade Eduardo Mondlane in Mozambique; and Institut Sénégalais de Recherches Agricoles (ISRA) in Senegal. Other partners are the International Institute of Tropical Agriculture (IITA) headquartered in Nigeria and USA’s Feed the Future Innovation Labs for Collaborative Research on Grain Legumes and for Climate Resilient Cowpeas.

It’s a lot easier and quicker, and certainly less hit-or-miss than traditional methods!… By eliminating some phenotyping steps and identifying plants carrying positive-trait alleles for use in crossing, they will also shorten the time needed to breed better-adapted cowpea varieties preferred by farmers and markets.”

Cowpea seller at Bodija Market, Ibadan, Nigeria.

Cowpea seller at Bodija Market, Ibadan, Nigeria.

 

On target, and multiplying the score
[First, a rapid lesson on plant-genetics jargon so we can continue our story uninterrupted: ‘QTLs’ stands for quantitative trait loci, a technical term in quantitative genetics to describe the locations where genetic variation is associated with variation in a quantitative trait. QTL analysis estimates how many genes control a particular trait. ‘Allele’ means an alternative form of a the same gene. Continuing with the story…]

The curved shape means that these cowpea pods are mature and ready for harvesting.

Culinary curves and curls: the curved shape means that these cowpea pods are mature and ripe for harvesting.

“We first verified 30 cowpea lines as sources of drought tolerance and pest resistance,” Phil recalls. “Using molecular markers, we can identify the genomic regions of the QTLs that are responsible for the desired target phenotype, and stack those QTLs to improve germplasm resistance to drought or pests. It’s a lot easier and quicker, and certainly less hit-or-miss than traditional methods! However, standing alone, QTLs are not the silver bullet in plant breeding. What happens is that QTL information complements visual selection. Moreover, QTL discovery must be based on accurate phenotyping information, which is the starting point, providing pointers on where to look within the cowpea genome. Molecular breeding can improve varieties for several traits in tandem,” suggests Phil. “Hence, farmers can expect a more rapid delivery of cowpea varieties that are not only higher-yielding, but also resistant to several stresses at once.”

And what are Phil and team doing to contribute to making this happen?

The genomic resources from Phase I – especially genotyping platforms and QTL knowledge – are being used in Phase II of the TLI Project to establish breeding paradigms, using molecular breeding approaches,” Phil reveals. He adds that these approaches include marker-assisted recurrent selection (MARS) and marker assisted back-crossing (MABC). “These paradigms were tested in the cowpea target countries in Africa,” Phil continues. “By eliminating some phenotyping steps and identifying plants carrying positive-trait alleles for use in crossing, they will also shorten the time needed to breed better-adapted cowpea varieties preferred by farmers and markets.”

… best-yielding lines will be released as improved varieties… others will be used…as elite parents…”

Future work
What of the future? Phil fills us in: “The advanced breeding lines developed in TLI Phase II are now entering multi-location performance testing in the target African countries. It is expected that best-yielding lines will be released as improved varieties, while others will be used in the breeding programmes as elite parents for generating new breeding lines for cowpeas.”

Clearly then, the job is not yet done, as the ultimate goal is to deliver better cowpeas to farmers. But while this goal is yet to be attained and – realistically – can only be some more years down the road, it is also equally clear that Phil and his team have already chalked up remarkable achievements in the quest to improve cowpeas. They hope to continue pressing onwards and upwards in the proposed Tropical Legumes III Project, the anticipated successor to TLI and its twin project TLII – Tropical Legumes II.

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