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Development of resilient cowpea varieties by the application of Marker Assisted Breeding (MAB) for the West and Central Africa Sub-Region

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The cowpea improvement research team at the Institute of Agricultural Research for Development (IRAD), Centre de Maroua, Cameroon. Left to right: Dr Liliane Iyale, Dr Arlette Zaiya Zazou, Dr Sobda Gonné, Ms Merline Fankou, Ms Yvonne Djeoufo, Mr Dieudonné Gnapou and Mr David Amedep.

PROJECT OVERVIEW

Background

 

The Kirkhouse Trust (KT) cowpea breeding programme in Cameroon focuses on the improvement of two varieties important in the country: Lori and Vya. In the first phase of the project, Lori and Vya were respectively crossed to IT98K-205-8 and IT99K-573-1-1, two varieties resistant to the parasitic weed Striga, a major constrain to cowpea production in Cameroon. Backcross breeding populations were developed, and selection was assisted by the use of C42B-2B, a molecular marker linked to the gene conferring Striga resistance in IT98K-205-8 and IT99K-573-1-1. Resistance to Striga was also confirmed by growing the plants in the screen house in pots with soil containing Striga seeds: the weed is only able to germinate and grow on susceptible plants.

 

Two Striga resistant improved Lori derived varieties IR15 MA02 and IR15 MA33 (Lori-2 and Lori-3) were released in 2019. They are very similar but differ in seed size. The release of Vya derived Striga varieties is to follow: three promising lines were identified in 2019 (IR16 MA-P; IR16 MA-K and IR16 MA-A) and are currently being evaluated.

 

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Improved Striga resistant Lori-derived varieties released in Cameroon in 2019: IR15 MA02 (i and ii) and IR15 MA33 (iii and iv).

Efforts to introduce other key characteristics into the improved Lori and Vya varieties were also started in the previous phase of the project: an aphid resistant variety originally from Ghana, SARC1-57-2, was crossed to IR15MA 02 and to IR15MA 33. Insect resistance in the breeding population is traced using the molecular marker CP171/CP172 to select plants that combine Striga and insect resistance.

The July 2021 edition of the Kirkhouse Trust newsletter was dedicated to the Cameroon team. Read it here.

Objectives

 

The overall goal of the cowpea improvement programme is to develop farmer preferred cowpea varieties resistant or tolerant to multiple constraints to production (Striga, insects, and key diseases in the region) which are well adapted to the Sudano-Sahelian zone of Cameroon, using modern molecular breeding tools. The objectives of the current grant (Jan 2020-Dec 2022) are:

 

  1. To complete the development and release of a Striga resistant improved Vya variety.

  2. To complete the introduction of resistance to aphids into the Striga resistant improved Lori and Vya varieties.

  3. To initiate a marker assisted backcross breeding programme to develop cowpea varieties resistant or tolerant to Brown blotch disease, caused by the fungal pathogen Colletotrichum capsici.

  4. To initiate a marker assisted backcross breeding programme to develop cowpea varieties resistant or tolerant to Fusarium, another important fungal pathogen.

  5. To initiate a marker assisted backcross breeding programme for early maturing cowpea.

Progress to date

  1. The Striga resistant improved Vya varieties (IR16 MA-K and IR16 MA-P) were evaluated in four field locations with high levels of Striga infestation: Guiring, Soukoundou, Djlingo and Yagoua. In terms of yield, the highest values of 1,869.8 Kg/ha (pod yield) and 1,632.1 Kg/ha (grain yield) were obtained from lines IR16 MA-P at Guiring followed by 1,481.1 Kg/ha (pod yield) and 1,375.8 Kg/ha (grain yield) from lines IR16-MA-K at Yagoua.

  2. BC2F1 breeding populations developed from a cross between the Striga resistant Vya derived varieties (IR16 MA-K and IR16 MA-P) and the aphid resistant donor variety SARC-1-57. BC4F3 populations were developed from the cross between the Striga resistant Lori-derived varieties (IR15 MA02 and IR15 MA33) and SARC-1-57.

  3. Disease resistant and early maturing  cowpea varieties used in other West African cowpea breeding programmes were gathered to identify potential donors. Screen house trials to identified sources of Colletotrichum and Fusarium resistance were performed.

  4. Colletotrichum infected cowpea samples were collected from farmers’ fields the main cowpea production areas in the Northern Cameroon (Mayo Danay, Mayo sava, Mayo Tsanaga, Mayo Kani, Diamaré and Bénoué). Single spore isolation and characterisation have been completed, and the pathogenicity test was performed.

  5. Cowpea samples infected with Fusarium were collected at IRAD in the 2020 cropping season. Ten Fusarium strains were isolated, and the pathogenicity test was carried out on known Striga resistant Lori-derived varieties resistant and susceptible varieties (CB46 and IT99K-573-2-1, respectively, both from Nigeria).

  6. A total of twenty-five (25) cowpea genotypes were collected and screened at the experimental farm of IRAD Maroua at Guiring during 2020 cropping season under natural rainfall conditions. Agronomic characteristics, including time to maturity, were recorded. Sanzi, CB27 and IT00K-1217 recorded the shortest duration for flowering. CB27 had the largest seed size, followed by Sanzi and IT00K-1217.

  7. Backcross breeding programmes to introduce earliness and Fusarium resistance into Striga resistant Lori-derived varieties have been initiated.

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Cowpea plants growing in pots on soil containing seeds of Striga to select resistant plants resistant to the parasitic weed, pictured are (i) susceptible plants because Striga weed were able to germinate and grew (arrow); (ii) aphids feeding on the young leaves of a cowpea seedling ; (iii) Dr Gonné making crosses in the greenhouse ; (iv) IR19 MA33 field trials, 2019.

PROJECT TEAM MEMBERS

 
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Dr Sobda Gonné

Principal Investigator, Institut de Recherche Agricole pour le Développement (IRAD), Centre de Maroua, Cameroon.

Dr Gonné, a former KT PhD Scholar, has led the KT-funded cowpea improvement programme in Cameroon since its inception in 2008. He holds a Master's degree in Crop Protection from the Catholic University of Leuven, Belgium, and a PhD from the West Africa Centre for Crop Improvement (WACCI), entitled “Genetic studies of cowpea [Vigna unguiculata (L.) Walp.] for resistance to thrips (Megalurothrips sjostedti Trybom) in Cameroon".

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Dr Arlette Zaiya Zazou

Molecular Breeder

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Dr Liliane Iyale Laboratory Technician

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Mr David Amedep Data Management Scientist

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Mr Dieudonné Gnapou

Data Management Scientist

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Ms Yvonne Djeoufo

Data Management Scientist

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Mr Pierre Metsena

PhD Student

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Ms Merline Fankou 

Plant Pathologist

PhD Student

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Ms Sophie Yanne

MSc Student

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Ms Julienne Dieu Donnée

MSc Student, University of Maroua

Graduated 2021

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Mr Kalib Safta

MSc Student, University of Maroua

Graduated 2017 

STUDENT PROJECTS

Development of cowpea varieties tolerant/resistant to  Colletotrichum capsici (Brown blotch disease) adapted to the agro-ecology conditions of north Cameroon

 

Ms Merline Fankou

MSc in Plant Breeding, University of Maroua, Cameroon. Graduated 2018.

Supervisors: Dr Goudoum Augustin, University of Maroua, Dr Sobda Gonné, Institute of Agricultural Research for Development, Centre of Maroua.

Project objectives

  1. Identify Colletotrichum spp responsible for brown blotch diseases of cowpea in Cameroon.

  2. ​Characterize Colletotrichum isolates found in cowpea fields in Cameroon.

Achievements:

  1. The two most pathogenic isolates identified and characterised: MD3a and MK25.

  2. Two potential donors for resistance to brown blotch identified: KN-1 and Ife brown.

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Ms Fankou characterising Colletrotrichum isolates under the microscope.

From left to right, (i) collection of diseased cowpea plants in the field; (ii) diseased samples examined under the microscope; (iii) Ms Fankou making single spore Colletrotrichum isolates under the microscope; (iv) Ms Fankou explaining students how to count fungal spores during a pathology training.

Genetic diversity study of a cowpea (Vigna unguiculata Walp.) population using microsatellite markers in the Northern Region of Cameroon

 

Mr Kalib Saftia

MSc in Plant Breeding, University of Maroua, Cameroon. Graduated 2017.

Supervisors: Dr Dorothy Tchatchoua Tchabda, University of Maroua, Dr Sobda Gonne, Institute of Agricultural Research for Development, Centre of Maroua.

Project objectives

  1. Determine the agromorphological characteristics of a cowpea germplasm collection.

  2. ​Differentiate cowpea genotypes based on molecular marker information.

Achievements:

1. High variability found among the cowpea genotypes surveyed.

2. The marker CP171/172 associated with Striga resistance was found to be the most        polymorphic between the gentotypes tested.

Genetic studies of cowpea [Vigna unguiculata (L.) Walp.] for resistance to thrips (Megalurothrips sjostedti Trybom) in Cameroon

 
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Mr Saftia in the laboratory.

Dr Sobda Gonné

PhD in Plant Breeding, West Africa Centre for Crop Improvement (WACCI), University of Ghana, Legon. Awarded 2017.

Supervisors: Professor Pangirayi Tongoona, University of Ghana; Professor Jonathan Ayertey, University of Ghana; Dr Ousmane Boukar, IITA/IRAD; Professor Mike Timko, University of Virginia.                 

Background

Thrips are an important cowpea insect pest in Cameroon, and heavy infestation can result in complete loss of harvest. Thrips are usually controlled by the application of insecticides, however this measure is ineffective, represents and additional cost to production and are toxic for humans and the environment. This study was carried out as part of the requirements for a PhD with the following objectives:

 

  1. To identify new source of resistance to flower bud thrips through the screening of germplasm.

  2. To determine the inheritance of resistance to thrips in cowpea.

  3. To identify QTLs associated with resistance to flower bud thrips in cowpea.

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Dr Gonné on his PhD graduation day, 2017.

Achievements

  1. Two hundred (200) cowpea varieties including 180 landraces were screened for resistance to thrips in two field locations (Guiring and Djalingo) and in the screenhouse (IRAD), scoring visual damage to flowers and the number of thrips per flower. Eleven thrip resistant varieties were identified, including Sanzi, from Ghana.

  2. Two sets of six generations (P1, P2, F1, F2, BC1P1, BC1P2) developed from crosses between Sanzi (resistant parent) and Vya and Lori (susceptible parents) were evaluated under artificial and natural thrips infestation. The generation mean analysis revealed that both additive and non-additive gene action were important with dominance x dominance being the most predominant. Broad sense and narrow sense heritability estimated varied from 0.58 to 0.74 and 0.61 to 0.65 for number of thrips per flower and rating of thrips damage, respectively, indicating the influence of the environment on thrips susceptibility. The number of genes controlling thrips resistance was three for number of thrips per flower and between 3 and 4 for score of thrips damage.

  3. One hundred and fifty (150) F2 plants derived from a cross between Sanzi and Vya were used to construct a genetic map with 232 polymorphic SNP markers. Three significant QLTs (Fthp129, Fthp28 and Fthp87) for thrips resistance were detected accounting for 43.2% of the observed phenotypic variation. Further studies are needed to validate these QTLs for their useful exploitation in a molecular breeding programme.

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Left to right, (i) thrips on a cowpea flower; (ii) typical symptoms of cowpea flowers attacked by thrips; (iii) collection of flowers infested by thrips, also used to artificially infest plants in the screenhouse to determine the susceptibility or resistance to thrips of tested plants; (iv) the F2 mapping population derived from Sanzi and Vya grown in the screen house; (v) sampling of leaf tissue from the mapping population for DNA extraction and analysis.

PUBLICATIONS

 
  • Metsena, P., Kosma, P., Fankou, D.M.Y and Ndouvahad, L. (2021).  Identification of Fusarium oxysporum sf tracheiphilum strains responsible of cowpea wilt in Far-north region of Cameroon. Journal of Applied Biosciences 164: 17001-17011.

  • Iyale L., Noubissie J.B., Mapongmetsem P.M., . and Djile B. (2018). Genetic screening of cowpea varieties [Vigna unguiculata (L.) Walp.] for Aphis craccivora resistance in the Sudano-Sahelian Zone of Cameroon. Asian Journal of Biotechnology and Genetic Engineering 1: 1-15.

  • Gonné, S., Mewounko, A., Sakati, P.D. and Ndaodeme, K., 2018. Farmers' cowpea production constraints and varietal preferences in the Sudano-Sahelian zone of Cameroon. International Journal of Innovation and Applied Studies 24: 968-977.

  • Gonné, S., Atemkeng, F.M., Boukar, O., Fatokun, C., Tongoona, P.B., Ayertey, J. and Offei, S.K., 2018. Generation mean analysis in cowpea [Vigna unguiculata (L.) Walp.] under flower thrips infestation. Journal of Agricultural Science 10: 86.

  • Gonné, S., Boukar, O., Tongoona, P.B., Ayertey, J. and Offei, K.S., 2017. Quantitative trait loci (QTL) for cowpea resistance to flower bud thrips (Megalurothrips sjostedti Trybom). International Journal of Plant Breeding and Genetics 4: 292-299.

  • Gonné, S., Venasius, W.L. and Laminou, A., 2013. Characterization of some traditional cowpea varieties grown by farmers in the Sudano-Sahelian zone of Cameroon. International Journal of Agriculture and Forestry 3: 170-177.

 

PROJECT LOCATIONS

Research Station, Cameroon