A success tale on improving two legume crops in Africa

Ousmane Boukar (o.boukar@cgiar.org), Tahirou Abdoulaye, Manuele Tamó, Hesham Agrama, Hailu Tefera, Christian Fatokun, and Steve Boahen
O. Boukar, Cowpea Breeder; T. Abdoulaye, Socioeconomist, IITA, Ibadan, Nigeria; M. Tamó, Legume Entomologist, IITA, Benin; H. Agrama and H. Tefera, Soybean Breeders, IITA, Malawi; C. Fatokun, Cowpea Breeder, IITA, Ibadan, Nigeria; S. Boahen, Legume Specialist/Agronomist, IITA, Mozambique

Cowpea and soybean are cultivated by poor and middle-income farmers as a sole crop or as intercrop with maize and other cereals for their protein-rich grains which are consumed in different forms. The haulms from plant residues and the dry pod walls of both crops are good sources of quality fodder for livestock.

Improved cowpea varieties being tested in a field trial. Photo by L. Kumar.
Improved cowpea varieties being tested in a field trial. Photo by L. Kumar.

The two crops contribute substantially to sustain crop production through their ability to fix atmospheric nitrogen, some of which is left behind in the soil after harvesting for subsequent crops. IITA and its partners have been involved in improving legume production systems for several decades. An overview of these efforts is presented in this article.

Cowpea
Cowpea―indigenous to sub-Saharan Africa (SSA), is grown on about 14 million ha worldwide, with over 84% of this area in SSA. Between 1985 and 2007, the rate of growth was 4.5% in land area planted to cowpea, 4.5% in grain yields/ha, and 5.9% in quantity of cowpea produced. These data indicate that the increase in the quantity of grain produced over the period resulted mainly from an expansion in the land area and less from an improved yield/unit area. In well-managed experimental stations, yields of up to 2 t/ha can be obtained but globally the average yield is about 450 kg/ha.

Several abiotic and biotic factors keep the productivity of cowpea low in African farmers’ fields. Notable among these are drought, poor soil fertility, inappropriate agronomic practices, an array of fungal, viral, and bacterial diseases, and parasitic flowering plants (Striga and Alectra). Cowpea is particularly susceptible to infestation by several insects with devastating effects on plants in the field and seeds in storage.

Efforts in genetic improvement have been and are still being made to develop varieties with resistance to these various yield-limiting factors and in various research institutions across SSA, iIITA, and other advanced research institutions. Cowpea breeders from these various institutions meet regularly to share information and exchange ideas on the way forward.

Elite lines generated from IITA’s breeding nurseries are shared with interested colleagues from the national research institutions who evaluate these at their stations and in farmers’ fields. Those that perform well are recommended for release in the respective countries. For example, in Mali, a cowpea line IT99K-499-35 was recently adopted by many farmers in the Segou area and because of its superior performance and resistance to Striga, given a local name, Jinguiya which means ‘hope’.

Under the Tropical Legumes II (TL II) project, several new cowpea varieties [IT97K-499-35 (in 2008), IT89KD-288 and IT89KD-391 (in 2009), IT99K-573-1-1 and IT99K-573-2-1 (in 2011)] were released in Nigeria. Regional trials are being conduced for two cowpea lines (IT97K-1122 and IT00K-1263) identified through farmers’ participatory selection as part of the TL II project in Tanzania to facilitate their official release. In 2011, three IITA cowpea lines (IT97K-1069-6, IT00K-1263, and IT82E-16) were released in Mozambique; and IT99K-494-6 was released by Bunda College in Malawi as an Alectra-resistant variety in 2011.

Legume scientists in a disease resistance screening trial. Photo by L. Kumar.
Legume scientists in a disease resistance screening trial. Photo by L. Kumar.

Research into integrated pest management (IPM) for cowpea has resulted in the development and deployment of biopesticides including the use of entomopathogenic organisms combined with botanicals, and biological control agents such as hymenopteran parasitoids which attack and feed on some of the cowpea pests. An example is the mixture of a specific entomopathogenic virus capable of infecting and killing the legume pod borer Maruca vitrata with aqueous formulations of neem oil. This has proved to be as effective as the use of conventional insecticidal sprays. With regard to biological control, a small parasitic wasp which attacks the flower bud thrips, another major pest of flowering cowpea, has been introduced and established in most of Bénin and parts of Ghana, It has been reported to reduce the thrips population on wild alternative host plants by up to 40%.

The development of improved cowpea varieties has so far depended on conventional breeding methods. However, efforts are being made to apply molecular breeding tools to cowpea improvement. Fairly saturated genetic linkage maps of cowpea have been produced in several laboratories. The linkage maps have been used for the detection of DNA markers associated with resistance/tolerance to Striga, drought, macrophomina, and bacterial blight, and seed characteristics such as size. A few of the markers have been converted to user-friendly markers which will make them readily available for breeders in the national systems. Molecular markers are contributing to progress in variety development.

IITA is collaborating with Purdue University, USA, in implementing the Purdue Improved Cowpea Storage (PICS) project on the hermetic storage of cowpea grain in Nigeria, Bénin, Togo, and Cameroon. From 2008 to 2010, IITA and its partners disseminated hermetic triple-layer bags for storage in more than 13,500 villages in the cowpea-producing areas of Nigeria, Cameroon, Togo, and Bénin. This project addresses one of the most important constraints to cowpea production which is grain damage in storage. Furthermore, by not using any type of chemical, this hermetic storage method is protecting farming families and consumers from accidents from the mishandling of and poisoning by the chemicals used in cowpea storage. To date, farmers have purchased more than 30,000 PICS bags in these countries.

IITA is also collaborating in an adoption study that will provide information about the reach of the technology. Another study on analysis of the supply chain of the PICS bags in the same four countries will help to improve the farmers’ access to the PICS bags through a better distribution network.

Soybean
Soybean is a fairly new crop in SSA and has few biotic constraints. Fewer than 400 ha were planted to soybean in SSA during the 1980s but this exceeded the 1-million ha mark by 2007. Grain yield/ha increased from about 900 kg/ha in the 1980s to >1000 kg/ha between 2005 and 2007. Initially most varieties grown in parts of SSA had the problem of seed longevity. Farmers could not store seeds successfully from one cropping season to the next. This problem has now been solved so that seeds of the newly developed varieties remain viable over a longer period. Another constraint to soybean production was pod shattering, which resulted in seeds being lost in the field. Farmers could not leave their crop to dry in the field before harvesting without losing some of the grain. The varieties that have been developed at IITA have tolerance to pod shattering, and resistance to rust─a fungus (Phakopsora pachyrhizi) that causes significant yield losses, especially in the moist savanna agroecology. Some genotypes of soybean are noted for their abilities to reduce the seed bank of Striga hermonthica, a parasitic weed which can cause serious damage to cereal crops.

Farmers admiring improved soybean varieties. Photo by IITA.
Farmers admiring improved soybean varieties. Photo by IITA.

Several elite lines from IITA’s breeding nursery have been evaluated in many countries in SSA and found to perform well in farmers’ fields. Some of these have been recommended for release in the different countries. For example, rust-resistant TGx1835-10E and TGx1987-62F have been released in Nigeria; TGx1740-2F was released in Malawi; TGx-1485-1D, TGx1740-2F, TGx1904-6F, TGx1908-8F, and TGx1937-1F were released in Mozambique in 2011. These were the first batch of varieties ever released in Mozambique. The development of improved varieties also involved farmers’ participation in selection, which made it possible for farmers to have some knowledge on performance of the lines being selected, thus facilitating rapid adoption and dissemination. IITA, in collaboration with Laval University in Canada, completed genotypic [using single nucleotide polymorphism (SNP) markers] and phentotypic characterization of 300 soybean genotypes for rust resistance and symbiotic performance.

In addition to efforts on genetic improvement of soybean, major emphasis has been placed on promoting and using soybean to encourage consumption, and thus create markets for farmers to sell their produce. Recipes were developed to promote the use of soybean grain for food. This promotional activity was necessary because the crop was new in many parts of the region and people were not familiar with how it could be best used as food. Vegetable oil millers were also encouraged to accept soybean as a raw material from where good quality oil could be extracted.

Legumes fix atmospheric nitrogen in their root nodules through the symbiotic association between the crop and rhizobium, a free-living soil bacterium. Legume seeds are inoculated with the rhizobium before sowing to increase the number of rhizobium available to the plant for infection and nodule formation, and subsequently enhance the quantity of the nitrogen fixed. Soybean is one such crop that requires rhizobium inoculation if a good crop is to be established on soils with no existing rhizobia or inadequate number if rhizobia.

At IITA, some soybean varieties have been developed which are capable of fixing atmospheric nitrogen using the native rhizobium present in the soil. These varieties which require no inoculation before sowing are characterized by promiscuous nodulation. Growing such varieties will save the farmers some expense and the time needed to purchase the inoculants with which the seeds are treated.

Conclusions
Decades of collaborative research efforts on genetic improvement of these two important legume crops involving scientists in the national agricultural research systems of different countries in SSA, IITA, and advanced research institutions in Europe and North America have resulted in the development and promotion of different improved varieties to meet the preferences of farmers and consumers. Improved varieties developed through this partnership have been released in over 70 countries around the world, which signifies the success of this partnership for legume crop improvement.

Further efforts will focus on use of innovative approaches to pyramid pest and disease resistance genes into improved lines and varieties; application of molecular markers to rapidly introduce genes for simply inherited desirable traits into popular varieties; and genetic modification using recombinant DNA technology to produce insect-resistant cowpea varieties (Bacillus thuringiensis or Bt cowpea for resistance to the Maruca pod borer). Efforts will be continued to address diseases, such as the need to develop improved cowpea and soybean lines with combined resistance to different fungal, bacterial, and viral pathogens. The factors that influence tolerance to drought in cowpea require further elucidation, as this would facilitate progress in developing new varieties with enhanced drought tolerance.

Better soybean

Two African nations—Malawi and Nigeria—have released three improved soybean varieties that can enhance the productivity of the crop and offer farmers better opportunities.

The varieties are TGx1740-2F, TGx1987-10F, and TGx1987-62F. TGx1740-2F was developed by IITA in collaboration with the Department of Agricultural Research Services (DARS) in Malawi. Varieties TGx1987-10F and TGx1987-62F were developed by IITA in collaboration with Nigeria’s NCRI.

The Malawi Agricultural Technology Clearing Committee officially approved the release of TGx1740-2F in January 2011 while the Nigeria Varietal Release Committee released TGx1987-10F and TGx1987-62F in December 2010.

The varieties outperformed the standard and local checks grown in the two countries, with high grain yield in multiple locations under on-station and on-farm trials.

Many farmers preferred the varieties because they smother weeds and reduce the cost of weeding. Farmers that participated in the on-farm trials of the varieties last year said they preferred them especially for their golden color at maturity.

In Malawi, TGx1740-2F gave the highest mean grain yield of 2.5 t/ha. It exceeded the yield of checks, grain variety Nasoko by 10% and the widely grown promiscuous variety Magoye by 32% during the two-year multilocation on-station trials.

The variety performed equally well during on-farm participatory variety selection trials in four districts of central Malawi. In the 2009/10 season, it outyielded all the new types of soybean varieties under testing with 2.2 t/ha. It also surpassed Nasoko by 15% and Magoye by 38%.

High in nutritive value, soybean is fast gaining appeal in Africa, offering a cheap source of protein. The crop is also emerging as an important feed, food, and raw material for producing high-quality protein products. For smallholder farmers it is an important cash crop and also improves soil fertility because of its ability to fix high amounts of atmospheric nitrogen.

Rust-resistant soybean

TGX1835-10e, a rust-resistant soybean. Photo by IITA
TGX1835-10e, a rust-resistant soybean. Photo by IITA
A new soybean variety that is resistant to the deadly Asian soybean rust—a fungal disease that could wipe out as much as 80% of infested crops—has been released. The rust-resistant soybean is the first of its kind to be made available for cultivation in West and Central Africa and has the potential of increasing soybean production in rust-prone areas of the region.

Tagged TGx 1835-10E, the variety was bred by scientists at IITA and further developed in collaboration with Nigeria’s National Cereal Research Institute (NCRI).

“The variety is high yielding, averaging 1.6 t/ha grain and 2.2 t/ha fodder in field trials in Nigeria,” says Olumide Shokalu, NCRI pathologist who conducted the trials. It is also early maturing, has good promiscuous nodulation, and resists pod shattering and other prevalent diseases.

“The variety can be used for direct cultivation in tropical Africa or as a source of resistance genes. It was previously released in Uganda through Makerere University, and has already shown excellent performance in trials carried out in Southern Africa, suggesting that it is a well-adapted variety,” says Hailu Tefera, IITA soybean breeder.

30 years R4D in soybean: what’s next?

Forty years ago, only a handful of farmers in Benue State, middle belt of Nigeria were growing soybean. The crop was generally thought more suitable for large-scale commercial growing and industrial processing. But not anymore.

This golden bean is grown in the farms of resource-poor smallholders in the Guinea savannas of Nigeria and other parts of sub-Saharan Africa.

“In the 1970s, there was little interest and effort in Africa to grow and improve soybean because of extremely low yields and seed viability, poor nodulation, high shattering rate, and limited postharvest use,” reported Dr Hailu Tefera, soybean breeder and OIC of IITA-Malawi, on 30 years of IITA soybean breeding work.

Breeding gains

When IITA started improvement research in 1974, the average yield per hectare in Africa was 660 kg/ha. Total production was only 0.2 million tons. Thirty years later, using IITA-developed varieties, the average yield in West African countries increased by more than 50%, and 67% in the whole of Africa, equivalent to 1.1 t/ha over 20 years of breeding effort. That is a genetic gain of more than 2% per year in grain yield.

Twenty-one African countries now produce soybean. Nigeria has the highest 6-year (2000-05) average production of 486,000 tons on an area of 553,260 hectares, followed by South Africa with 205,270 tons from 122,870 hectares, and Uganda with 155,500 tons from 139,500 hectares.

Soybean production increased dramatically, Tefera said, as locally adapted tropical germplasm was developed and distributed to other African countries. In Nigeria, the soybean industry quickly advanced. Integrated processing, use, and marketing aspects followed efforts to develop improved cultivars. This is a testament to IITA’s research for development (R4D) in soybean that produced high-yielding and stable varieties, tolerant or resistant to biotic and abiotic constraints, and promoted processing and use.

Community impact

In 1985, to improve nutrition and to create demand, IITA began the development of small-scale and home-level food processing technologies. A study funded by the International Development Research Centre (IDRC) Canada with the Institute for Agricultural Research and Training (IART), Ibadan, Nigeria, after 3 years found that soybean had been successfully used to increase the protein content of traditional foods. New products—flour, milk, baby food—had been developed and introduced. Small-scale processing machines were introduced. Over 25,000 people in the rural areas were trained, with training project sites increasing from 3 to 27. The number of farmers growing soybean in target villages increased by 35%. Sales of grain and flour soybean increased in Nigerian markets.

Phase 2 of the project covered all Nigeria with several national institutions such as IART; National Cereals Research Institute, Badeggi; National Agricultural Extension Research and Liaison Services, Zaria; and the University of Nigeria at Nsukka. An assessment of four states in 1992 showed wide commercialization.

Markets had increased from 2 in 1987 to 42 in 1993. The number of retailers ballooned from 4 in 1987 to 824 in 1993. In Benue State, more women were involved in soybean production. New IITA varieties were widely adopted and grown by 9% of farmers in 1989 to 75% in 1997 on 30% of the area planted to soybean in the state.

So far, Tefera reports, some 17 IITA-bred tropical soybean varieties have been released by national agricultural research and extension systems (NARES) of several West and Central African countries (Nigeria, Benin, Ghana, Democratic Republic of Congo, Togo),  and Uganda. These show considerable increases in grain and fodder yields, improving soil fertility in the savannas and enhancing the yields of subsequent crops such as maize and sorghum. Since 2000, however, support for soybean research among the NARES has declined. On-farm variety testing and releases is at a standstill, except for MAKSOY 1N, an early maturing variety resistant to rust, a destructive foliar disease, in Uganda.

Potential for expansion

Soybean growing suitability map. IITA
Soybean growing suitability map. IITA

IITA recently expanded breeding of its West Africa-bred varieties to Southern Africa, where cultivation by small-scale farmers is rising because of less susceptibility to pests and disease, better grain storage quality compared with other legumes, large leaf biomass, and a secure commercial market. Commercial soybean farms are now found in South Africa, Zimbabwe, and Zambia.

In South Africa, the Agricultural Research Council develops cultivars with better adaptation and seed quality, high yield, resistance to nematodes and rust, and tolerance to low night temperatures. It is also developing genetically modified drought-tolerant soybean—the first soybean GMO in South Africa. Twenty-one members of the South African National Seed Organization produced 2,879 tons of soybean seed in 2006-07.

SeedCo in Zimbabwe breeds varieties for the local market and other countries in the region; these are resistant to red leaf blotch and frogeye disease. It produces inoculants that go with the varieties. The Zambia Seed Company produces, processes, and markets seeds of various crops including soybean and is considering testing IITA-developed varieties under Zambian conditions.

“Soybean improvement efforts in the past focused on helping subsistence farming,” said Tefera. “Currently many African countries are practicing market-oriented agriculture to increase farmers’ income and reduce poverty. Soybean improvement work at IITA should consider technologies for use by farmers of different capacities.”

According to FAO, Africa spent US$1 billion in 2004 to import soybean and soy oil. Of this, US$752 million was for soybean oil and US$254 million was for soybean grain/meal. Countries such as South Africa, Malawi, Zimbabwe, and Zambia in aggregate produce 33.4% of Africa’s total production.

Producing enough in the region and adding value can save millions spent on imports for other development activities, he further added. There are also export possibilities to Europe and Japan as soybean grown in Africa is mostly non-GMO.
Favorable government policies are needed to develop the soybean industry in Africa. In Brazil and Argentina in the 1990s, economic reforms created favorable conditions for agricultural investment, production, and exports. Research alone was not the driving force for the soybean industry’s impressive growth there.

Market-oriented policy changes included elimination of export taxes, lifted restrictions on import of agricultural inputs, privatization of marketing and transportation infrastructure including state-owned grain elevators, port facilities, and railroads. Farmers also invested heavily in new technologies that improve yields, accelerate planting and harvesting, and facilitate delivery.

“Achieving these targets requires the efforts of various players in research, production, and marketing,” Tefera concluded, “and should consider technological, institutional, and organizational interventions in both the supply and demand sides.”