Improved cowpea varieties for Nigeria’s savannas

Nigeria has released two new cowpea varieties to raise production and improve farmers’ incomes.

Harvesting cowpea. Photo by IITA
Harvesting cowpea. Photo by IITA

The varieties—IT89KD-288 and IT89KD-391—were developed by scientists working at IITA, Ibadan, in collaboration with the Institute for Agricultural Research of the Ahmadu Bello University, Zaria; University of Maiduguri, Borno; and the Agricultural Development Programs of Borno, Kaduna, Kano, and Katsina States.

Both varieties have proven to be superior over the current improved lines being cultivated. They could be used to overcome the challenges faced by cowpea farmers in the country.

For instance, IT89KD-288 (now SAMPEA-11) is a dual-purpose cowpea variety with large white seeds and a rough seed coat. It has combined resistance to major diseases including septoria leaf spot, scab, and bacterial blight, as well as to nematodes, and tolerance for Nigeria’s strain of Striga gesnerioides (a parasitic weed that severely lowers yield).

“It also has a yield advantage of at least 80% over the local varieties,” said Alpha Kamara, IITA Agronomist, who is leading efforts to rapidly disseminate the varieties to farmers.

The nematode-resistant variety is an equally good candidate for sowing with cereals or as a relay crop with maize in the moist and dry savanna zones, and for high grain production in the dry season.

Scientists recommend that the variety be planted in mid-July in the Sudan savanna, early to mid-August in the northern Guinea savanna, and by the end of August in the southern Guinea savanna. However, if there is certainty of rains up till the end of October, IT89KD-288 can be planted in September.

Cowpea farmers in Kano, Nigeria. Photo by IITA.
Cowpea farmers in Kano, Nigeria. Photo by IITA.

IT89KD-391 (now SAMPEA-12) is also a dual-purpose cowpea variety but it has medium-to-large brown seeds with a rough seed coat. These are preferred seed characteristics for commercial production in northeast Nigeria.

“IT89KD-391 is a welcome improvement over SAMPEA 7, Ife brown, IT90K-76, and IT90K-82-2 which are the main improved brown-seeded varieties available. It has been tested extensively in this area and is well accepted by the farmers,” said Hakeem Ajeigbe, IITA Extension/Dissemination Specialist.

“The variety performs well as a sole crop and an intercrop. It could also be planted as a relay crop with maize in the Guinea savannas,” he added.
Several on-station and on-farm trials have shown that IT89KD-391 (SAMPEA 12) produces double the yields of local cultivars.

In 2008, Nigeria released a Striga-resistant improved cowpea variety (IT97K-499-35).

“The demand for these improved varieties is high because of their superior yields and their acceptability by consumers,” Kamara said.

Using molecular tools to develop Striga-resistant cowpea

Striga-infested field. Photo by IITA.
Striga-infested field. Photo by IITA.

Witchweed, Striga gesnerioides (Willd.), continues to be a major menace to production in West and Central Africa, where cowpea is an important crop.

This parasitic weed feeds on cowpea plants, leading to severe chlorosis or yellowing, wilting, stunting, and even the death of susceptible hosts. Annual yield losses are estimated in millions of tons.

Collaborative project
A collaborative project funded by the Generation Challenge Program has taken a close look at the Striga problem and is using molecular tools to identify new sources of resistance. Marker-assisted selection or breeding (MAS or MAB) is being used to facilitate the selection of lines with resistance to Striga. In 2008 and 2009, the Institut National de l’Environnement et des Recherches Agricoles (INERA) of Burkina Faso and IITA undertook a study to identify potential sources of Striga resistance, worked with farmers to articulate their problems and preferences, and tested new Striga-resistant improved lines developed using MAS.

Prior to the breeding activity, participatory rural appraisal (PRA) and farmers’ participatory variety selection (FPVS) sessions were organized in seven Striga hot-spots in Niger and Burkina Faso, which are major cowpea-producing areas. During the 2 years, in Niger, 403 farmers contributed to the FPVS and several of their preferred cowpea lines were selected.

To determine farmers’ preferences in Niger, germplasm of 24 cowpea varieties with various characteristics (seed color, seed size, plant type, maturity, and Striga resistance) were planted in farmers’ fields and used for the PRA and FPVS. The same 24 accessions were also planted in two fields at IITA’s Minjibir Experimental Farm as checks.

Trial sites for 2009 FPVS activities in NIger and Nigeria
Trial sites for 2009 FPVS activities in NIger and Nigeria

In Niger, researchers and local agricultural agencies worked with farmers in their fields. Based on interviews and responses to questionnaires, farmers acknowledged that Striga is a serious problem that seems to be increasing, said IITA scientists Satoru Muranaka and Ousmane Boukar, and Jean Baptiste Tignegre of INERA, who collaborated on the project. Farmers, they added, also suggested that the use of resistant varieties could be a solution. This reconfirmed the importance of Striga resistance as a breeding goal.

The project has also confirmed farmers’ preference for IT00K-1148 and IT90K-372-2-1 because of their agronomic traits. These lines are susceptible to the dominant race of Striga in Niger. In the FPVS, farmers preferred new lines, such as KVX30-309-6G and TN256-87, which also lacked resistance to Striga.

Of the top five genotypes selected by the farmers in the seven locations, only two—IT99K-573-2-1 and IT98K-205-8—were picked by farmers because these met their preferences for Striga resistance, early maturity, and high yield potential.

Farmers preferred the white-seeded variety for consumption but genotypes with brown seed color that are early maturing and high yielding were also acceptable. The surveys and FPVS activities showed that farmers use consistent selection criteria based on various traits.

Because of unstable rainfall and other problems in 2009, farmers did not get good grain yields, although in a few cases, Striga-resistant IT99K-573-2-1 showed 4−6 times more grain yield (average 214 kg/ha compared with 37−51 kg/ha for local varieties).

Both IT99K-573-2-1 and IT98K-205-8 showed resistance to Striga in all the locations used for the trial. These varieties could be recommended for cowpea production in Southeastern Niger where Striga and drought are major constraints, and for use as sources of resistance genes in breeding other varieties.

Marker-assisted breeding
Using MAB, pot and field experiments in 2008 and 2009 evaluated backcrossed varieties (crossed to their parents) for various traits, such as resistance to Striga, flowering and maturing dates, disease resistance (to bacterial blight, virus, and leaf rust), and seed characteristics.

Farmers selecting cowpea varieties in Niger. Photo by IITA.
Farmers selecting cowpea varieties in Niger. Photo by IITA.

Of the 60 genotypes tested in a pot screening trial in the Maradi station of the Institut National de Recherche Agronomique du Niger (INRAN) from October 2008 to November 2009, 18 showed Striga resistance. Results confirmed that the Striga race (SG3) dominant in two locations in northern Nigeria is also dominant in the four trial locations in southeastern Niger. Field trials had been conducted earlier in Kano and Borno States in Nigeria. Hence, the same Striga-resistant genetic resources could be used for breeding varieties for these areas.

Two existing sequence characterized amplified region (SCAR) markers, 61R and MahSE2, were earlier identified to have the potential for use in MAB for SG3 Striga resistance. To confirm this, pot experiments were conducted using Striga-resistant lines that had been developed using MAS. Results showed a higher percentage of resistant plants in the MAB-developed populations than in the control (those that did not use MAB). SCAR marker MahSE2 showed 88% and 96% marker efficiency for evaluating Striga resistance in backcrossed populations.

Pyramiding or building up Striga resistance in these breeding lines via MAB is important. However, further exploration of appropriate markers is needed to develop efficiently the varieties preferred by farmers. Likewise, more markers linked to various traits that meet farmers’ preferences identified in the PRA and FPVS also need to be converted to SCARs for use in MAB.

This project was able to identify germplasm lines with resistance to Striga races predominant in the Niger Republic; identify farmers’ constraints and preferences to aid in selecting for important traits to combine with Striga resistance; and conduct with farmers the participatory field testing of the new Striga-resistant improved lines developed via the MAB method. It also confirmed the efficiency and effectiveness of MAB for Striga resistance