African yam bean: a food security crop?

Daniel Adewale, d.adewale@cgiar.org

Read the Ukranian translation by Martha Ruszkowski

Diversity in color, color pattern, structure, texture, brilliance, etc. of African yam bean seeds. Photo by D. Adewale, IITA.
Diversity in color, color pattern, structure, texture, brilliance, etc. of African yam bean seeds. Photo by D. Adewale, IITA.

Biodiversity assures the evolutionary continuity of species. The collection and conservation of diversity within species are a safeguard against the loss of germplasm. They provide a buffer against environmental threats and assure continual and sustainable productivity. Global food security is becoming shaky with increasing dependence on a few major staple crops. This has resulted in an alarming reduction not only in crop diversity but also in the variability within crops.

The conservation and maintenance of agrobiodiversity of neglected and underutilized plant species such as African yam bean (AYB) in seed banks aim at contributing to food security and preventing a potential food crisis. Increasing the use of underutilized crops is one of the better ways to reduce nutritional, environmental, and financial vulnerability in times of change (Jaenicke and Pasiecznik 2009); their contribution to food security is unquestionably significant (Naylor et al. 2004, Oniang’o et al. 2006). Among other things, the consumption of a broader range of plant species ensures good health and nutrition, income generation, and ecological sustainability.

Potentials of African yam bean
The plant (Sphenostylis stenocarpa) is one of the most important tuberous legumes of tropical Africa. It is usually cultivated as a secondary crop with yam in Ghana and Nigeria. A few farmers who still hold some seed stocks, especially the white with black-eye pattern, plant it at the base of yam mounds in June or July. The crop flourishes and takes over the stakes from senescing yam. It flowers and begins to set fruits from late September and October. The large bright purple flowers result in long linear pods that could house about 20 seeds.

The seed grains and the tubers are the two major organs of immense economic importance as food for Africans. This indigenous crop has huge potential for food security in Africa. However, there are cultural and regional preferences. In West Africa, the seeds are preferred to the tubers but the tubers are relished in East and Central Africa (Potter 1992). The crop replaces cowpea in some parts of southwestern Nigeria (Okpara and Omaliko (1995). Researchers (Uguru and Madukaife 2001) who did a nutritional evaluation of 44 genotypes of AYB reported that the crop is well balanced in essential amino acids and has a higher amino acid content than pigeon pea, cowpea, and bambara groundnut.

Tuber yield per stand of AYB accession TSs96 at Ibadan, 2006. Photo by D. Adewale, IITA.
Tuber yield per stand of AYB accession TSs96 at Ibadan, 2006. Photo by D. Adewale, IITA.

Apart from the use of soybean as an alternative to animal protein, protein from other plant sources is not often exploited. The protein content in AYB grains ranged between 21 and 29% and in the tubers it is about 2 to 3 times the amount in potatoes (Uguru and Madukaife 2001, Okigbo 1973). AYB produces an appreciable yield under diverse environmental conditions (Anochili 1984, Schippers 2000). Another positive contribution of the crop to food security is the identification of the presence of lectin in the seeds, which could be a potent biological control for most leguminous pests.

Biodiversity
Although the vast genetic and economic potentials of AYB have been recognized, especially in reducing malnutrition among Africans, the crop has not received adequate research attention. Up to now, it is classified as a neglected underutilized species or NUS (Bioversity 2009). Devos et al. (1980) stressed that the danger of losing essential germplasm hangs over all cultivated food crop species in tropical Africa, especially those not receiving research attention. The quantity and availability of AYB germplasm is decreasing with time. At one time, Klu et al. (2001) had speculated that the crop was nearing extinction; its inherent ability to adapt to diverse environments (Anochili 1984, Schippers 2000) may have been responsible for its continual existence and survival. Nevertheless, scientists think that the genetic resources of AYB may have been undergoing gradual erosion.

IITA keeps some accessions of the crop, but otherwise, its conservation in Nigeria is very poor and access to its genetic resources is severely limited. Seeds of AYB seem to be available in the hands of those who appreciate its value, i.e., the elderly farmers and women in a few rural areas in Nigeria. The ancient landraces in the hands of local farmers are the only form of AYB germplasm; no formal hybrid had been produced as yet.

Improvement of the crop is possible only when the intraspecific variability of the large genetic resources of the species is ascertained. The genetic resources of AYB need to be saved for use in genetic improvement through further exploration in tropical Africa and for conservation.

African yam bean plant showing mature pods ready for harvest. Photo by Daniel Adewale, IITA.
African yam bean plant showing mature pods ready for harvest. Photo by Daniel Adewale, IITA.

Understanding AYB
Eighty accessions (half of the total AYB collection under conservation in the IITA genebank) were assessed for diversity using morphological and molecular methods. Thirty selected accessions were further tested in four ecogeographical zones in Nigeria to understand their productivity and stability. The breeding mode was also studied.

Findings show that each of the 80 accessions of AYB has a unique and unmistakable genetic entity, promising to be an invaluable genotype as a parent for crop improvement. Morphologically, two groups have evolved: the tuber forming and the nontuber forming.

Grain yield differed among individual accessions and across the four agroecologies. The average grain yield across the four diverse environments in Nigeria (Ibadan, Ikenne, Mokwa, and Ubiaja) was ~1.1 t/ha; however, grain yield at Ubiaja was well above 2 t. Most agronomic and yield-determining traits had high broad sense heritability and genetic advances, assuring high and reliable genetic improvement in the species. AYB is both self fertilizing and an outcrosser; the latter trait is exhibited at about 10%.

The good news is improvement through hybridization is possible within the species.

References
Anochili, B.C. 1984. Tropical Agricultural Handbook. Pages 48–50 in Food Crop Production. Macmillan Publishers, London, UK.

Bioversity International. 2009. http://www.bioversityinternational.org/scientific_information/themes/neglected_and_underutilized_species/overview.html [25 February 2010].

Devos, P., G.F. Wilson, and E. Delanghe. 1980. Plantain: Genetic resources and potential in Africa. Pages 150–157 in Genetic Resource of Legumes in Africa edited by Doku, E.V. Proceedings of a workshop jointly organized by the Association for the Advancement of Agricultural Science in Africa and IITA, Ibadan, Nigeria, 4–6 January 1978.

Jaenicke, H. and N. Pasiecznik. 2009. Making most of underutilized crops. LEISA Magazine, 25(1):11–12.

Klu, G.Y.P., H.M. Amoatey, D. Bansa, and F.K. Kumaga. 2001. Cultivation and uses of African yam bean (Sphenostylis stenocarpa) in the Volta Region of Ghana. The Journal of Food Technology in Africa 6:74–77.

Naylor, R.L., W.P. Falcon, R.M. Goodman, M.M. Jahn, T. Sengooba, H. Tefera, and R.J. Nelson. 2004. Biotechnology in the developing world: a case for increased investment in orphan crops. Food Policy 29:15–44.

Okigbo, B.N. 1973. Introducing the yam bean (Sphenostylis stenocarpa) (Hochst ex. A. Rich.) Harms. Proceedings of the first IITA Grain Legume Improvement Workshop, 29 October–2 November 1973, Ibadan. Nigeria. pp. 224–238.

Okpara, D.A. and C.P.E. Omaliko. 1995. Effects of staking, nitrogen and phosphorus fertilizer rates on yield and yield components of African yam bean (Sphenostylis stenocarpa). Ghana Journal of Agricultural Science 28:23–28.

Oniang’o, R.K., K. Shiundu, P. Maundu, and T. Johns. 2006. Diversity, nutrition and food security: the case of African leafy vegetables in Hunger and poverty: the role of biodiversity. Report of an International Consultation on the role of biodiversity in achieving the UN Millennium Development Goal of freedom from hunger and poverty edited by Ravi, S.B., I. Hoeschle-Zeledon, M.S. Swaminathan, and E. Frison. Chennai, India, 18–19 April 2005. M.S. Swaminathan Research Foundation, Chennai, India. pp. 83–100.

Potter, D. 1992. Economic botany of Sphenostylis (Leguminosae). Economic Botany, 46: 262-275.

Schippers, R.R. 2000. African indigenous vegetables: An overview of the cultivated species. Natural Resources Institute/ ACP-EU Technical Centre for Agricultural and Rural Cooperation, Chatham, UK. pp. 89–98.

Uguru, M.I. and S.O. Madukaife. 2001. Studies on the variability in agronomic and nutritive characteristics of African yam bean (Sphenostylis stenocarpa Hochst ex. A. Rich. Harms). Plant Production and Research Journal 6:10-19.

Dominique Dumet: Safeguarding agrobiodiversity for the future

Dominique Dumet showing seeds, IITA genebank. Photo by J. Oliver.
Dominique Dumet showing seeds, IITA genebank. Photo by J. Oliver.

As the head of IITA’s Genetic Resources Center (GRC), Dominique Dumet says she is something between a curator and an administrator. She is involved in conservation (field bank, seed bank, and in vitro bank, which includes cryopreservation for clonal crops), checking inventory, improving processes and workflows, transferring technology, and computerizing the system. In addition, she is involved in recruiting staff and selecting students, germplasm distribution and acquisition, research in plant genetic resources, staff management, research project development and proposal writing, and communication to donors on special projects and about germplasm at IITA during scientific meetings.

She is primarily interested in ex situ conservation and particularly low temperature biology and its application to conservation systems (cryopreservation, sanitation). She has an overview of all domains of germplasm conservation and takes part in various research projects as a collaborator to “add value to the germplasm.” She no longer considers herself a researcher, since she spends most of her time administering the genebank and planning or writing proposal or reports. This International Year of Biodiversity, she explains what GRC plans in support of promoting biodiversity conservation.

Why is biodiversity conservation important? What are your priorities?
Our work is very important. We try to reduce the rate of irreversible loss in the biological diversity that is used in agriculture. All conservation aspects are important, but maybe the conservation sensu stricto comes first if we have to choose as we have a responsibility towards the international community and if we do not work well, all may suffer from our mistakes.

What do you like about working in Africa? In your field of specialization?
I am proud of my job. I hope I contribute to improving the well being of the poorest even if for one iota. I also like being in an environment very different to the one in which I grew up.

In vitro biology and cryopreservation in particular is my field of specialization. Cryopreservation fascinates me as I find it amazing that we can stop the life of a tissue and bring it back again whenever we want to do so. In the frozen stage, all biochemical or biological processes stop—that means that everything stops moving at one moment—and then the magic of life makes it start again so long as physical and chemical parameters are adequate (cooling and thawing temperature, osmotic pressure, light, growth regulators, etc.).

What are your challenges and constraints at work?
The challenges are to maintain the bank at international standards and to keep all the accessions alive. Some constraints include unforeseen requests which make us work under pressure as we still have our routine activities, and new concepts that make our system obsolete.

Collection recording with barcode inventory system, IITA genebank. Photo by O. Adebayo, IITA.
Collection recording with barcode inventory system, IITA genebank. Photo by O. Adebayo, IITA.

How do you make the many visitors to GRC understand and appreciate what you are doing?
I give information on the basic concepts of diversity, I explain why we need to conserve it ex situ (out of the natural environment) because of the genetic erosion taking place in the field. Then I explain how we maintain it via seeds or field and in vitro banks, depending on the crop. I also show some examples of diversity, e.g., cowpea seed collection and the variation observed at seed coat. I provide some background on the gaps in the collection based on GIS. And I generally conclude with the International Treaty and access to plant genetic resources for food and agriculture (PGRFA).

Please cite some concrete steps being taken by IITA in biodiversity conservation.
IITA was involved in collecting genetic resources as early as the 1970s so we do have a long history in investing in biodiversity conservation. Many collecting missions have been organized and germplasm has been also acquired from many national collections. The majority of the collections have now been described at agromorphological level, but we are still working on it for maize, for example. We have to characterize any new accessions coming into the bank.

Recently we organized a meeting and survey to develop the cowpea global conservation strategy (Trust-funded). We will have the same strategy developed for yam in 2010 (we are also organizing the Trust-funded expert meeting for this). We are developing more efficient conservation processes such as cryopreservation (this lowers costs but also limits genetic variation during storage). We are fingerprinting the collections of clonal crops to identify germplasm at accession level. This will further guide our collecting missions.

Do you think governments everywhere are serious about biodiversity conservation?
That depends on the country. The richer ones certainly take more serious action—but the poorest (or the less organized) do not have this ‘luxury’. I think all understand the value of biodiversity but as it is a long-term investment to store and as the return on investment is not guaranteed, countries either ignore it or do little about it.

What is the state of agrobiodiversity in Africa?
It is not too bad, compared to other continents—my view on this is that Africa has not yet undergone its Green Revolution (but this opinion may be controversial). However, things may change very quickly, especially now that Africa is seen as a big field where agriculture can take off. Somehow, if we are successful in producing high-yielding crops the adoption rate of such high potential crops may quickly wipe away natural diversity, including (but not only) the landraces (varieties developed by farmers over thousands of years). When the elite genotype replaces older varieties it makes the low performing one obsolete and it increases the rate of planting (as it can generate higher revenue). We have to be vigilant about this since we, as breeders of improved varieties, are partly responsible. There is a conflict of interest between agriculture intensification and conservation of biodiversity.

Do farmers understand the need to conserve seeds or genetic resources for future generations?
In general I would think they are the first one to know about biodiversity but they may not be aware of the amplitude of the “erosion” of species.

Some are already organized in community based genebanks and there are participatory conservation projects within the CGIAR but I do not know enough about the topic. This may be an important complementary approach, but participatory conservation may be difficult to sustain. Besides in community based conservation, the incentive is cultural preference. That means only materials of immediate interest for the farmers are kept.

Bambara groundnut seeds. Photo by J. Oliver, IITA.
Bambara groundnut seeds. Photo by J. Oliver, IITA.

What is the status of IITA’s seed shipment to Svalbard in Norway?
We had planned on sending more than 20,000 accessions of cowpea and its relatives, bambara groundnut, maize, and soybean in the next few years. Cowpea makes up the majority of the accessions that we are sending. There is a bit of deviation from the original plan but we are more or less on track.

Being the lead person in agrobiodiversity conservation in the Institute, how do you plan to mark the UN International Year of Biodiversity?
We plan to raise awareness about biodiversity among the youth, i.e., high school students and adults in the local community. We will organize quiz contests, tree planting activities, excursions to the IITA forest and to the genebank; produce information materials (videos, flyers, handouts) and set up roaming exhibits and posters.

We also plan to organize seminars and a field or biodiversity/community day for students, farmers, and residents in the local community. We will be coordinating with partners from the University of Ibadan, local schools, Alliance Française, and other organizations, such as the National Center for Genetic Resources and Biotechnology, Nigeria Institute of Horticulture, and University of Abeokuta.

What would be your message to colleagues about biodiversity conservation?
Don’t just conserve; educate as well.

Robert Asiedu: Advancing the development of Africa through science

Robert Asiedu. Photo by IITA.
Robert Asiedu. Photo by IITA.

Robert Asiedu is a plant breeder, whose main research interest is on tropical root and tuber crops, especially yam and cassava. From the International Maize and Wheat Improvement Center (CIMMYT) he joined the Root and Tuber Improvement Program of IITA in 1989. His initial research was on cassava and its wild relatives but he spent most of his time on yam research. He has held various leadership or management roles in IITA since 1991. He is Director, Research for Development (R4D), West Africa, and Program Director, Agrobiodiversity and Root and Tuber Systems Programs. In this interview, he talks about research on root and tuber systems, and on agrobiodiversity initiatives.

What inspires you at work?
The potential to advance the development of Africa through agricultural research is a major inspiration for me. IITA offers an excellent platform for achieving this so it is a great pleasure and a privilege to work here.

What do you like about your work as director?
I enjoy the broader opportunities and challenges the position offers to contribute to the development of the subregion through science.

How do you feel about IITA’s work in West Africa and in those areas that you are in charge of as program director?
West Africa is the subregion in which the Institute has worked longest. It is fascinating to reflect on the changes in our modes of operation and interaction with partners in response to the changes in our environment. We have done well so far but there is still a
lot to do.

What is your work philosophy?
To do the best I can every time.

You talk about yam as being a “part of man”. What is so special about yam?
My thoughts on the links between man and yam are based on several fascinating articles by anthropologists and ethnobotanists that I have read on the subject. From West Africa through the Caribbean to the Pacific region, yam is respected and celebrated through major annual thanksgiving festivals in areas where it is cultivated as a staple.

How is progress on IITA’s R4D on roots and tubers/ Agrobiodiversity?
The R4D work on tropical root and tuber crops continues to focus on genetic improvement, crop and pest management, food science and technology, and agroenterprise development.

For yam, improved options for the mass production of affordable and healthy seeds are a major component of our agenda. We have been investigating nutrient use efficiency and the role of mycorrhizal fungi in yam mineral nutrition. The research on food science/technology is focused on understanding the functional properties required in yam tubers and products for household and industrial purposes, development of new competitive products from yam, and screening of germplasm for textural and nutritional attributes.

We continue to improve on our efficiency and effectiveness in conserving the germplasm of banana/plantain, cassava, cowpea, maize, soybean, and yam. Core collections and reference sets are being defined. These collections are characterized using molecular tools and several are being preserved in the form of DNA available for delivery to requestors. Documentation of information has been improved and are now available online. There has been a significant increase in the accessions of clonally propagated crops that are preserved in vitro, in addition to the field banks.

What are the challenges in working on roots and tubers? Agrobiodiversity?
The limited history of research on the tropical root and tuber crops, such as cassava and yam, has left huge gaps in the knowledge of their basic biology. This affects the pace of advancement in research, compared to that of other major staple crops. This is exacerbated by the limited pool of researchers on these crops worldwide. Research funding is very low compared with the importance of these crops in sub-Saharan Africa.

In Agrobiodiversity, the major challenges are the lack of clarity in the interpretation of various international conventions, increasing protectionism in the sharing of crop germplasm, and the apparent lack of international agreements governing the status of collections of nonplant taxa.

What can you advise colleagues?
We should constantly keep our focus on the status, needs, and expectations of those who will benefit from our work.

How could we make the partnership with national programs, donors and policymakers, the private sector, or the growers work better?
Successful partnerships are built on good foundations. Establishing partnerships involve the joint setting and common understanding of the objectives, sharing of responsibilities, and clarity of roles. Periodic and objective assessment of progress is necessary, followed by effective action on the findings. There should be mutual respect and trust in the relationship as well as regular, effective, and open communication. It is important to monitor the changing circumstances of the various partners, including institutional and policy environments, and the needs of some partners for capacity building to play their roles effectively. Good cooperation also depends on fairness in acknowledging the contributions of partners and equity in sharing results, credits, or benefits.

How would you assess IITA’s efforts in agrobiodiversity conservation?
IITA has played and continues to play a key role in conserving germplasm of staple crops, underutilized crop species, and nonplant taxa that are important to African agriculture. Most national programs in sub-Saharan Africa have difficulty in providing the facility and personnel required for long-term conservation of these materials, especially the clonally propagated crops. The duplication of national collections of selected crops in our genebank is a major contribution to the assurance of long-term security. IITA works with a range of partners to continually improve the methods of preservation and characterization of the conserved germplasm.

How can we promote agrobiodiversity conservation among our audiences?
We can increase information dissemination using the print and electronic media and stakeholder consultative workshops to highlight the benefits of sustaining diversity in the food and farming systems and hence in the genetic resources on which these depend. The long-term conservation of nonplant genetic resources, such as beneficial insects and bacteria, requires even more explanation. Taking advantage of our political neutrality and links with relevant international agencies, we can engage in more consultation with policymakers in Africa to allow more freedom in making new collections of germplasm and facilitating international exchange.