Yield and pest resistance of elite cowpea breeding lines.
Cowpea is an important grain legume because it is a major source of cheap dietary protein. In the last four decades, the production of cowpea in South Africa is limited by lack of improved varieties that exhibit good agronomic traits and pest resistance. The purpose of the study was to develop cowpea varieties with important economic traits to meet the needs of the farmers. Germplasm lines were evaluated in field trials to select the promising lines that were used in hybridization to develop well-adapted elite genotypes. Pair-wise crosses were made to develop broad-based segregating populations. Pedigree, recurrent selection methods were used to advance the promising genotypes. Ten genotypes expressed high grain yield with combined pest resistance (aphids, bruchid, virus, leafhopper and bacterial blight). The implication of this achievement is that farmers can attain more grain yield per land area with reduced cost of pest control and increase the profit margin of the farmers. Furthermore, four elite varieties (JanaFod, ARC-GCI-CP76, UL-58 and UL-1010) have been registered and awaiting commercialization. The future activity is to commercialize the varieties to enhance uptake and availability of seeds to seed growers, farmers and consumers.
- breeding lines
- grain yield
- pest resistance
- quality traits
- Vigna unguiculata
Cowpea is an important grain legume because it is a major source of cheap dietary protein which ranges from 23 to 32% [1, 2, 3] and 64% carbohydrate  that complements the over dependence on low-protein staple cereals and potatos in South Africa. The largest production of this crop is in sub-Saharan Africa, where it is a staple food crop and feed for animals . Cowpea can be prepared in different forms (boiled as pudding and soup, steamed as
1.1 Word cowpea production
According to DAFF  the world annual cowpea grain production is about 3 million tons that is produced on 12.5 million hectares but only a small proportion enters the international trade. West and Central Africa is the leading cowpea producing regions in the world, producing 64% of the estimated 3 million tons of cowpea seed that is produced annually. Nigeria is the world’s leading cowpea-producing country followed by Brazil. Other countries in Africa include, Senegal, Ghana, Mali and Burkina Faso. Ghana, Niger and Cameroon are significant producers. The major production areas elsewhere in the world are Asia (India, Myanmar) and America (USA, Brazil, West Indies). Conservative estimates suggest that greater than 12.5 million ha are planted annually to cowpea around the world. Of this area, about 9.8 million ha are contributed from West Africa, making it the region with the largest production of cowpea in the world [2, 11].
1.2 Cowpea production in South Africa
DAFF  reported that small-scale farmers are the major cowpea producers in South Africa under rain-fed farming conditions but there are no records regarding the size of area under production and yields produced. However,  reported that the land area used by farmers to produce cowpea ranges between 0.5 and 2.0 hectares per farmer. Farmers that cultivate land area up to two hectares make use of tractor or motorized implements  to save cost and to produce more above their family consumption and the excess is preserved for sale. The major cowpea producing areas in South Africa are Limpopo, Mpumalanga, North-West and KwaZulu-Natal . A study conducted by  showed that farmers grow cowpea for consumption and as source of income.
Farmers prefer important traits such as seed color, seed size, growth habit and early maturity varieties. This suggests the great opportunity that exists for the development of cowpea varieties with divers coat colors and high potentials for their demand and marketability. Based on the duration of rainfall, some farmers choose early maturing varieties, as this will assist the crop to escape moisture deficits and frost damage while others choose late maturing types because they are more interested on the fodder for livestock feeding. On the other hand, KwaZulu-Natal farmers preferred cowpea varieties based on growth habit . The diverse preferences by farmers call for the need to develop varieties with different agronomic and quality traits. The purpose of the research was to develop cowpea varieties that would overcome the various limitations encountered by farmers and to meet their needs. To develop varieties that will meet the needs of farmers and consumers, a well-tailored need assessment survey was conducted in some of the cowpea production areas between 2006 and 2007 . Through this survey, the dire needs of farmers and quality trait preferred by consumers were documented and used as the breeding objectives [13, 14]. Therefore aim of the research was to develop cowpea varieties that would overcome these constraints through a well-designed breeding programmes and activities while the specific objectives include:
Development of early maturing varieties (70–90 days). These are grain type of cowpea which are commonly cultivated in regions with short rainfall duration (Figure 1). In higher rain region, they can be used for double cropping (first cropping from October–December and second cropping from January to March). They are best varieties to use to evade terminal drought.
Development of Medium maturing variety (91–100 days). These are dual-purpose cowpea types. They are good for grain and fodder for animal feed (Figure 2).
Development of late maturing varieties (101–120 days). They are mainly for fodder and leafy vegetable production with limited seed production. The medium and the late cowpea types are of high value for integrated livestock production and rural livelihood in rural communities (Figure 3).
Development of high yielding varieties with multiple trait characteristics (adaptation and pest (insect and disease resistance). The prevalent insect pests include aphid, leafhopper, cowpea bruchid and blister beetles  and the diseases are bacterial blight, anthracnose as well as nematodes. Multiple pest resistance genes have been incorporated in most of the elite cowpea lines.
To develop high consumer quality trait varieties such as seed size, color, low cooking time and high protein content. To incorporate these quality traits in one commercial variety is practically impossible. Therefore, development of high yielding and pest resistance cultivars with different quality traits is the practice. Seed coat color and texture is an important consumer preferred quality traits. Large seed size with bright coat color command a high premium price in South Africa.
Common insect pests of cowpea
The common insect pests of cowpea include, cowpea aphids, leaf hopper (Figure 4), bruchid, blister beetles and pod-sucking bugs (Figure 5) . The economic importance of these insects vary from one location to another depending on the climatic variables that promote their abundance and the presence of their alternate hosts. It is important to note that the presence of winter for at least 4–5 months in some provinces has reduced drastically the carryover effects of some of these pests from one cropping season to another thereby reducing insect spectra and early incidence in South Africa unlike West Africa where there is no winter. Most of the breeding parents used for the development of the elite genotypes in South Africa were introduced from IITA-Nigeria and they possess multiple resistance to both aphid and bruchid, and were incorporated into the elite lines.
2. Materials and methods
One the major constraints to cowpea production in South Africa is lack of improved varieties. This was identified in the need assessment survey [7, 12]. To solve this constraint, international improved varieties were introduced in 2005/6 from International Institute of Tropical Agriculture (IITA), Nigeria for adaptive breeding purposes. Some of the varieties possess economic traits (high yielding, pest resistance and quality). The introduced varieties formed the breeding stock for the development of new adapted germplasm in South Africa. Based on the screening outcomes, promising varieties were selected for pair-wise crosses with promising local South African germplasm lines such as Glenda and Betchuana white to develop broad-based F2 population which was used to form the various segregation populations for the specific objectives. Some of the varieties possess economic traits (high yielding, pest resistance and quality). The introduced varieties formed the breeding stock for the development of new adapted germplasm in South Africa. Based on the screening outcomes, promising varieties were selected for pair-wise crosses with promising local South African germplasm lines such as Glenda and Betchuana white to develop broad-based F2 population which was used to form the various segregating populations for the specific objectives. Some of these genotypes were screened in hot spots (Bela-Bela and Taung) for adaptation and important traits (yield, aphid resistance, and diseases (bacterial blight and anthracnose) and advanced to subsequent generations. Between 2005 and 2007, intensive screenings were conducted on the segregation populations using Pedigree method. From F4−F8, segregating populations were subjected to selection and advancement (using pedigree selection method) in a replicated field trials for adaptation and validation of important economic traits [7, 14, 15]. From (F9–10)- an advanced fixed generation with promising genotypes from various traits for various specific objectives were tested in multiple locations for G X E [16, 17, 18] for adaptation. During the field evaluation processes, the populations were also subjected to aphids, bacterial blight, anthracnose screenings under natural infestation, and bruchid screening in the laboratory. Promising varieties selected from the evaluations were tested over seasons.
2.1 Data analysis
All the data collected were subjected to analysis of variance (ANOVA) procedure using Genstat Version 20 software. Means were separated using Duncan Multiple range Test (DMRT) at P < 0.05.
3. Results and discussion
3.1 Common insect pests of cowpea
The common insect pests of cowpea include, cowpea aphids, leaf hopper (Figure 4), bruchid, blister beetles and pod-sucking bugs (Figure 5) . Most of the breeding parents used for the development of the elite genotypes in South Africa were introduced from IITA-Nigeria and have multiple resistance to both aphid and bruchid, and were incorporated into the elite lines (Table 1). This suggests that the parental lines used to develop the elite breeding lines have high heritability and were able to transmit the genes to their offspring . The implication of the multipest resistance is that farmers can grow the varieties with reduced cost of pest control thereby enabling the farmers to maximize profit.
|Pedigree||Grain yield (kg/ha)||Fodder yield (kg/ha)||Aphid||Viruses||bruchid||Leafhopper||Bacterial blight|
|IT98K-962 X IT97K-499-35||1740.50bc||1987.70cd||R||R||R||R||R|
|IT98K-962 X IT98K-205-8||1928.50b||2679.70b−d||R||R||MR||R||R|
|IT98K-962 X TVX 3236||1557.90cd||3611.00a||R||R||MR||R||R|
|IT97K-497-2 X IT98K-962||1670.60b−d||2796.50a−c||S||R||R||R||R|
|IT97K-497-2 X Oloyin||1561.70cd||2658.10b−d||S||R||MR||S||MR|
|IT97K-497-2 X IT82D-889||1675.40b−d||2659.50b−d||S||R||MR||R||R|
|IT00K-1217 X IT98K-962||2595.20a||2633.10b−d||R||R||R||R||R|
|IT98K- 205-8 X Oloyin||1441.20d||2283.10b−d||R||R||MS||R||MR|
|IT98K-205-8 X IT98K-406-2||1807.50bc||2488.60b−d||R||R||R||R||R|
|IT90K-76 X Oloyin||1891.70b||3022.00ab||R||R||R||R||R|
|BW (Local check)||1858.70b||1934.20d||S||S||S||R||R|
|P-level (P < 0.05)||0.001||0.001|
3.2 Development of early maturing varieties (70: 90 days)
The performance of the extra-early and early maturing varieties developed are shown in Table 2. Early maturity was also bred with good quality traits (seed size and color), plant type (erect or semi-erect), high yield, as well as pest resistance [10, 19]. This is to increase the acceptability and adoption of the varieties. In addition, early maturing varieties are regarded as “climate smart” and water use efficient varieties [1, 15]. Farmers in drought-prone regions of Limpopo Province can successfully grow such varieties within the short rainfall duration in their environment. The varieties are also regarded as the grain type cowpea (Figure 1).
|Grain yield kg/ha||Maturity||100seed weight (g)||Grain yield kg/ha||Maturity||100seed weight (g)|
3.3 Development of medium maturing varieties (91: 100 days)
Medium maturity cowpea varieties were developed for regions with higher rainfall 600–750 mm per annum with summer rainfall duration of 3–4 months. Medium cowpea types are characterized with good grain and fodder yield and are often regarded as the dual-purpose cowpea (Table 3 and Figure 2) [20, 21]. They are also suitable for livestock integration. This type of cowpea also combine good quality traits (seed size and color) with, high yield, plant type (semi-erect) and pest resistance. The list of medium maturity cowpea are shown in Tables 2 and 4. Dual-purpose cowpea varieties under good rainfall distribution produce grain yield far above the grain type because it takes extra time to develop more photosynthetic apparatus such as leaves, canopy, branches and height which enables the varieties to produce flowers and more pods which are translated into high grain yield [19, 20, 21]. The high fodder yield is generated from the branches and leaves [2, 5].
|Variety||Grain yield kg ha−1||Fodder Yield kg ha−1||Maturity (days)||100 seed weight (g)||Harvest index|
|P Level (P < 0.05)||0.001||0.002||0.001||0.001||0.001|
|Variety||Grain yield (Kg ha −1)||Fodder yield||100 seed weight (g)||maturity (days)|
|P Level (P < 0.05)||0.001||0.0001||0.002||0.04|
3.4 Development of vegetable cowpea varieties
One of the ways that cowpea contribute to food security and nutrition is through the pods and leaves (Figure 3) which are eaten as vegetable to relish meals. This is an important cowpea menu in South Africa. It is locally called “
Vegetable varieties offer a regular source of income to farmers as they have easy buyers of their produce in the rural markets who sell the green pods with other leafy vegetables, spinach and lettuce. The adoption of these varieties will increase family intake and improve their diet and nutrition reduce malnutrition in rural communities [6, 7].
3.5 Development of cowpea varieties for intercropping
Intercropping is an integral part of cropping system in many provinces of South Africa particularly by smallholder farmers where communal land is limiting and drought-prone. In South Africa, many small scale farmers practice intensive crop production to reduce the risk of crop failure and maximize profit per unit area . Additional reason for intercropping is to reduce pest incidence. Specific varieties were developed with particular plant architecture and canopy structure designed for alternate row and double row cereal-cowpea intercropping system for maximization of land equivalent ratio (LER). Cowpea with narrow leaf blade and canopy width has been developed for alternate row intercropping system with cereals (Figures 7 and 8). They require reduced inter- and intra-row spacing for maximization of plant density per hectare. The varieties developed for intercropping particularly the early maturing varieties can always fit in any intercropping system. The implication of this is that the varieties increase the productivity and profitability of the farmers using poor marginal soils (Figure 8) [8, 14].
3.6 Development of cowpea varieties with combined pest resistance
One of the ways to reduce over dependence on chemical spray for the control of prevailing pest spectrum of cowpea is to develop varieties with increased host plant resistance. This has been achieved by deploying varieties with combined insect pest resistance as breeding parents to develop new germplasm with medium to high resistance to different insect pests (Table 1). The promising genotypes were screened for resistance for each insect pest for confirmation of resistance using appropriate screening technique [22, 23]. The elite lines with combined pest resistance have the advantage of requiring minimum insect spray. This will ultimately reduce production cost and increase the profit margin of the farmers.
3.7 Development of late maturing varieties (101: 120 days)
Few varieties were developed for late maturity. They are photosensitive and suitable for fodder and leafy vegetables (Table 5 and Figure 3). The fodder yield is very high with low grain yield. Some varieties if planted in October/November may not produce seed until the month of March when day length is shorter. To produce seed of such varieties, planting should be done during the first week of January while for fodder production planting can be done in the months of October or November. JanaFod is one of the late maturing varieties (Table 6 and Figure 3) developed for fodder and could produce 6000 kg ha−1 of haulm . The advantage of producing late maturing varieties is that it will enhance hay/fodder production particularly by commercial farmers who can use irrigation in their production system. The fodder produced can be bailed and sold to other farmers during offseason or farmers who cannot produce fodder for their animals. The fodder production from the developed varieties will enhance feed security for livestock industry in South Africa.
|Variety||Grain yield kg/ha||Fodder yield kg/ha||Maturity||100-Seed weight (g)||Harvest index|
|P-level (P < 0.05)||0.010||0.01||0.001||0.001||0.002|
|Variety||Fresh pod weight||Maturity||100-seed|
|Kg ha−1||(days)||weight (g)|
|TVu 2852||825 g||98b||15d|
|TVu 6477||721 g||107a||14.4e|
|TVu 14861||684 h||92c||15.8d|
|P Level (P < 0.05)||0.001||0.001||0.001|
3.8 Development of cowpea varieties for quality traits
Important quality traits apart from the nutrient elements addressed through breeding programme include, seed coat color, texture and size. These traits influence consumer preferences and demand pull . Fortification of the varieties with nutrients such as protein, zinc and iron is an integral part of our breeding activities. Elite varieties are subjected to nutrient analyses in search of varieties with higher nutrient contents to be used as breeding parents (Tables 7 and 8). To meet the needs of consumers, different seed coat, and eye colors (Figure 9) with different coat textures (smooth, rough and wrinkled) were developed. Consumers’ feedback suggests that rough and wrinkled seeds cook faster because they imbibe water faster during cooking as compared to smooth–coated varieties. These quality traits were achieved by crossing parents with different coat colors, eye colors and seed coat textures as well as seed size. The variation in nutrient content indicates variation in the genetic makeup of the varieties. The fortification of the varieties with nutrients especially zinc and iron will enhance the nutrition of the consumers and in addition, it offers opportunity for the varieties to be used for further crop improvement to generate new genotypes with higher nutrient contents. The different quality traits exhibited by the varieties give the farmers the opportunity to make choice and select their preferred varieties. This will improve their intake and nutrition and reduce malnutrition . The availability of the varieties will enhance food security and nutrition in South Africa. .
|Genotypes||Maturity days||Maturity periods||Seed weight||Seed size||Seed color||Eye color||Coat Texture|
|IT98K-962 X IT97K-499-35||94||Early||20.46||Large||White||Black||Wrinkled|
|IT98K-962 X IT98K-205-8||91||Early||18.30||Large||White||Black||Wrinkled|
|IT98K-962 X TVX 3236||96||Early||18.61||Large||White||Brown||Wrinkled|
|IT97K-497-2 X IT98K-962||93||Early||22.70||Large||White||Black||Rough|
|IT97K-497-2 X Oloyin||95||Early||18.60||Large||Cream||Brown||Smooth|
|IT97K-497-2 X IT82D-889||95||Early||20.52||Large||Brown||Brown||Smooth|
|IT00K-1217 X IT98K-962||96||Early||22.08||Large||White||Black||Smooth|
|IT98K- 205-8 X Oloyin||95||Early||19.28||Large||Brown||Black||Rough|
|IT98K-205-8 X IT98K-406-2||89||Early||19.39||Large||White||Black||Rough|
|IT90K-76 X Oloyin||94||Early||21.86||Large||White||Brown||Wrinkled|
|BW (Local check)||95||Early||15.67||Medium||White||Gray||Smooth|
|Variety||CP (%)||Zn (ppm)||Fe (ppm)|
3.9 Cowpea varieties registered and released
As many genotypes are in the pipeline of development and selection, some of the advanced breeding lines that have been test in multiple locations and seasons were submitted for registration with the intension to release them for commercialization. In the light of this, four cowpea varieties have been registered for a release at the National Department of Agriculture (DAFF), Genetic Resources, Pretoria. The varieties are:
JanaFod (ARC-09-001, ZA 20125043) cream cowpea
ARC-GCI-CP76 (VL 2009/7536) brown cowpea
UL-589 (VL 2017/10266) white cowpea
UL-1010 (VL 2017/10267) white cowpea
In addition, six early/medium maturity cowpea varieties have been submitted for registration at the National Department of Agriculture (DAFF), Genetic Resources, Pretoria and they include
These varieties upon registration and release will enhance the food and nutrition security of people in South Africa. Farmers will have seed of improved and pure varieties available to plant, and as they cultivate these varieties their profit margin will increase with better nutrition. This will also create jobs for all the value chain in cowpea production .
Cowpea production in South Africa is limited by lack of improved varieties that exhibit good agronomic traits and pest resistance. In the last decade and a half, significant breeding efforts as shown in the results of this study have attained great achievements in cowpea improvement to address the limitations in cowpea production. Several elite cowpea genotypes in the pipeline of development have been achieved, varieties that exhibit good agronomic and quality traits to enhance intake and nutrition in the rural communities have been developed 10 genotypes expressed high grain yield with combined pest resistance (aphids, bruchid, virus, leafhopper and bacterial blight). The implication of this achievement is that farmers can attain more grain yield per unit land area. In addition, the cultivation of these genotypes will reduce the cost of pest control and increase the profit margin of the farmers. Another important achievement of the study is that four elite varieties (JanaFod, ARC-GCI-CP76, UL-58 and UL-1010) have been registered while six varieties (UL-11, UL-12, UL-13, UL-14, UL-15 and UL-16) have been submitted for registration. The future activity is to commercialize the varieties to enhance uptake and availability of seeds to seed growers, farmers and consumers. The availability of seeds of these varieties will increase cultivation by farmers, enhance food security and nutrition and reduce malnutrition in South Africa. Since breeding is a continuous process, some of the varieties and other promising genotypes will be used through recurrent selection to develop new germplasm that are more adapted to the region as well as being climate smart.
The financial assistance of Department of Agriculture Fishery and Forestry, Pretoria, South Africa and Agricultural Research Council, Pretoria is gratefully acknowledged. The author is grateful for technical assistance from SandileNgcamphalala, Isaac Ntshalishali and Vuhlahani Thaphathi.
Hall AE, Thiaw S, Ismael AM, Ehlers JD. Water use efficiency and drought adaptation of cowpea. In: Singh BB, editor. Cowpea Research Advances. Ibadan, Nigeria: International Institute for Tropical Agriculture; 1997. pp. 87-98
Singh BB, Ajeigbe HA, Tarawali SA, Fernandez-Rivera S, Abubakar M. Improving the production and utilization of cowpea as food and fodder. Field Crops Research. 2003; 84:169-177
Asiwe, Joseph AN. Determination of nutrient and mineral contents of some selected cowpea lines for better quality trait improvement. Abstract, AGRI2017-Agriculture and Horticulture Conference, under subtitle-Food and Nutrients, 2-4 October, 2017, Park Inn, London, UK
Bressani R. Nutrient value of Cowpea. In: Cowpea Research, Production and Utilisation. Singh SR, Rachie KO, eds. UK: Chichester John Wiley and Sons; 1985 pp. 353-359
Tarawali SA, Singh BB, Peters M, Blade SF. Cowpea Haulms as Fodder. In: Advances in Cowpea Research. Singh BB, Mohan Raj DR, Dashiell KE, Jackai LEN. eds. Co-publication of International Institute of Tropical Agriculture (UTA) and Japan. Ibadan, Nigeria: International Research Center for Agricultural Sciences (JIRCAS) UTA; 1997. pp. 313-325
Asiwe JAN, Oluwatayo IB, Asiwe DN. Enhancing food security, nutrition and production efficiency of high-yielding grain legumes in selected rural communities of Limpopo Province, South Africa. In: Production Guide, Training of Farmers and Cowpea Processing, and Capacity Building. WRC Report No. TT 829/2/20. Pretoria, South Africa: Water Research Commission; Vol. 2. 2020b. ISBN: 978-0-6392-0176-4
Asiwe JAN, Oluwatayo IB, Asiwe DN. Enhancing food security, nutrition and production efficiency of high-yielding grain legumes in selected rural communities of Limpopo Province, South Africa. In: Research Report and Capacity Building. WRC Report No. TT 829/1/20 ISBN 978-0-6392-0176-4. Pretoria, South Africa: Water Research Commission; 2020a. Vol. 1. p. 169
Asiwe JNA, Maimela KA. Yield and economic assessments of five cowpea varieties in cowpea-maize strip intercropping in Limpopo province. South Africa International Journal of Agriculture and Biology. 2021; 25:27-32
Belane AK, Asiwe JAN, Dakora FD. Assessment of N2 fixation in 32 cowpea ( Vigna unguiculataL. Walp) genotypes grown in the field at Taung in South Africa, using 15N natural abundance. African Journal of Biotechnology. 2011; 10(55):11450-11458
Abaidoo R, Dare M, Killani S, Opoku A. Evaluation of early maturing cowpea ( Vigna unguiculata) germplasm for variation in phosphorus use efficiency and biological nitrogen fixation potential with indigenous rhizobial populations. The Journal of Agricultural Science. 2017; 155(1):102-116. DOI: 10.1017/S002185961500115X
Department of Agriculture, Forestry and Fisheries. Production Guideline for Cowpea. Pretoria, South Africa: Department of Agriculture Forestry and Fisheries; 2011. p. 5
Asiwe JAN. Needs for assessment of cowpea production practices constraints and utilization in South Africa. African Journal of Biotechnology. 2009; 8(20):5383-5388
Singh BB, Mohan Raj DR, Dashiell KE, Jackai LEN, editors. Advances in Cowpea Research. Ibadan, Nigeria: Co-publication of International Institute of Tropical Agriculture (UTA) and Japan International Research Center for Agricultural Sciences (JIRCAS). UTA; 1997
Singh B, Angira BB, Masor LL, Zhang M, Zhang H-B, Foster JL. Breeding next generation cowpea varieties for adaptation to changing climates and cropping systems. In: Abstract. Joint Pan-African Grain Legume and World Cowpea Conference on 28 February to 4 March 2016 at the AVANI Victoria Falls Resort (formerly the Zambezi Sun Hotel) in Livingstone, Zambia; 2016
Jackai LEN, Adalla CB. Pest management practices in cowpea: a review. In: Advances in Cowpea Research. Singh BB, Mohan Raj DR, Dashiell KE, Jackai LEN eds. Ibadan, Nigeria: Co-publication of International Institute of Tropical Agriculture (UTA) and Japan International Research Center for Agricultural Sciences (JIRCAS) UTA; 1997. pp. 240-258
Yan W, Kang MS. GGE Biplot Analysis: A Graphical Tool for Breeders, Geneticists, and Agronomists. Boca Raton, Florida: CRC Press; 2003. p. 288
Yan W, Tinker NA. Biplot analysis of multi-environment trial data: principles and applications. Canadian Journal of Plant Science. 2006; 86:623-645
Asiwe JAN, Sekgobela MM, Modiba PP. Heritability for morphological traits determine Adaptability of Elite Cowpea Genotypes in different environments. International Journal of Agriculture and Biology (IJAB). 2021; 26:105-114
Owusu EY, Akromah R, Denwar NN, Adjebeng-Danquah J, Kusi F, Haruna M. Inheritance of early maturity in some cowpea ( Vigna unguiculata(L.) Walp.) genotypes under rain fed conditions in Northern Ghana. Advances in Agriculture. 2018; 2018:10. DOI: 10.1155/2018/8930259
Kristjanson P, Tarawali S, Okike I, Singh BB, Thornton PK, Manyong VM, et al. Genetically Improved Dual-purpose Cowpea: Assessment of Adoption and Impact in the Dry Savanna Region of West Africa. ILRI Impact Assessment Series 9 ILRI (International Livestock Research Institute). Nairobi, Kenya, New York: John Wiley and Sons; 2001. pp. 68, 353-359
Dube E, Fanadzo M. Maximising yield benefits from dual-purpose cowpea. Food Security. 2013, 2013; 5:769-779. DOI: 10.1007/s12571-013-0307-3
Jackai LEN, Singh SR. Screening Techniques for Host Plant Resistance to Cowpea Insect Pests. Ibadan (Nigeria): Grain Legume Improvement Program, International Institute of Tropical Agriculture; 1988. p. 18
Asiwe JAN, Letsoalo IM. Response of introduced cowpea breeding lines to bruchid ( Callosobruchus rhodesianus) infestation in South Africa. Tropical Agriculture. 2018; 95:3
Gondwe TM, Alamu EO, Mdziniso P. Cowpea ( Vigna unguiculata(L.) Walp) for food security: An evaluation of end-user traits of improved varieties in Swaziland. Scientific Reports. 2019; 9:15991. DOI: 10.1038/s41598-019-52360-w