Pyramiding earliness, aphid and Macrophomina resistance in farmer preferred Striga resistant cowpea lines
Farmers’ field day organised by the CSIR-SARI KT cowpea breeding programme in Dimabi, Ghana, 2018.
PROJECT OVERVIEW
Background
The aphid species Aphis craccivora (Koch) is a major pest of cowpea across West Africa. The CSIR-SARI Kirkhouse Trust (KT)-funded cowpea breeding project kicked off in 2011 under the leadership of Dr Francis Kusi with the identification of SARC 1-57-2 as being resistant to aphid infestation, and with the recognition that the microsatellite locus CP171/172 is linked to the gene responsible for this resistance. The programme introduced this resistance gene by marker assisted selection into five popular Ghanaian cowpea varieties, namely IT99K-573-1-1, IT99K-573-3-2, Nhyira, Asetenapa and Zaayura.
The five improved cowpea varieties released by the CSIR-SARI programme funded by KT: Kirkhouse Benga (improved IT99K-573-2-1); Wang Kae (improved IT99K-573-1-1); Zaayura Pali (improved Zaayura); Soo-Sima (improved Nyira); and Diffeele (improved Asetanapa).
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This work resulted in the release in 2016 of Kirkhouse Benga (improved IT99K-573-2-1); Wang Kae (improved IT99K-573-1-1); Zaayura Pali (improved Zaayura); Soo-Sima (“Sweet Cowpea”, improved Nyira); and Diffeele (“Good Soup”, improved Asetanapa). For this work, Dr Kusi was awarded a PhD from the University of Ghana (thesis title: "Deployment of the cowpea aphid resistance gene for cowpea improvement in Ghana") in 2015, and in the following year, he won the national Best Agricultural Research Scientist Award.
The subsequent phase of the project aimed to add a second source of aphid resistance (present in the breeding line IT97K-556-6) to the improved varieties, with the intention of protecting them against resistance breakdown: this was the lead topic of Mr Patrick Attamah’s PhD research (who is expected to graduate late 2021).
Research conducted by Mr Salim Lamini focused on identifying sources of resistance and molecular markers for charcoal rot disease (caused by the fungus Macrophomina phaseolina), resulting in the identification of IT97K-573-1-1 as a source of resistance.
Mr Emmanuel Owusu’s PhD research has centred on the genetics of and breeding for early maturity, leading to the choice of the varieties Sanzi and CB27 as suitable donors to shorten the life cycle of local germplasm.
The current phase of the project (2021-2023), under the leadership of Mr Patrick Attamah, will develop improved Kirkhouse Benga and Wang Kae varieties that combine resistance to Striga, two genetic sources of resistance to aphids, resistance to Macrophomina, large seed size, and early maturity for terminal drought avoidance.
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An aphid infested cowpea seedling (i); artificial infestation with aphids in the screen house to test for susceptibility/resistance (ii); CSIR : SARI mobile screen house used for sampling aphids in several locations in Ghana to study the genetic diversity of populations (iii); the improved individual sleeve cage for testing individual plants for aphid resistance (iv).
PROJECT TEAM MEMBERS
Mr Patrick Attamah
Principal Investigator, Council For Scientific and Industrial Research-Savanna Agriculture Research Institute (CSIR-SARI)
Mr Attamah has recently become the PI of the KT cowpea improvement project. He completed his PhD in 2021 at the Kwame Nkrumah University of Science and Technology (KNUST), Ghana.
Dr Francis Kusi
Project mentor; Acting Director of CSIR-SARI; Head of the Upper East Farming System Research Group
Dr Kusi led the KT cowpea breeding programme from its inception in 2011 to 2021. A former KT PhD Scholar (Crop Sciences, Entomology, University of Ghana, 2015). The title of his thesis project is: Deployment of the cowpea aphid resistance gene for cowpea improvement in Ghana.
Mr Emmanuel Owusu
KT PhD Scholar, Kwame Nkrumah University of Science and Technology (KNUST), Ghana
Mr Salim Lamini
Research Scientist, KT PhD scholar, University of Ghana
Mr Frederick Awuku
Lab Manager, former KT MSc scholar
Ms Gloria Mensah
Lab Technician, former KT MSc scholar
Mr Mukhtaru Zakaria
Field Technician
Mr Anthony Nyaaba
Field Technician
Mr Frederick Agemge
Driver
STUDENT PROJECTS
Pyramiding of two different sources of aphid resistance genes into farmer preferred cowpea varieties in Ghana
Mr Patrick Attamah
PhD student, Kwame Nkrumah University of Science and Technology (KNUST).
Supervisors: Professor Richard Akromah, KNUST, Dr Francis Kusi, CSIR-SARI, and Dr Alexzander Wireko Kena, KNUST.
Background
Two aphid resistant cowpea varieties, SARC 1-57-2 and IT97K-556-6, were previously identified in CSIR-SARI. Resistance in these varieties was shown to be controlled by a single dominant gene, but the genes controlling resistance in SARC 1-57-2 and IT99K-556-6 are different, non-allelic and unlinked (located in two separate chromosomes).
Objective
The protection to aphids provided by two independent resistance genes is expected to be more durable than the protection conferred by a single gene.
The aim of the project was to combine the aphid resistant genes from the two parents into the five varieties previously improved by the CSIR-SARI cowpea improvement programme: Kirkhouse Benga (improved IT99K-573-2-1); Wang Kae (improved IT99K-573-1-1); Zaayura Pali (improved Zaayura); Soo-Sima (improved Nyira); and Diffeele (improved Asetanapa). Two molecular markers, SNP1_0912 and CP171/172, were used to select the IT97K-556-6 and SARC 1-57-2 aphid resistance genes in backcross progenies. The backcross populations were also tested for their susceptibility to aphids by artificial infestation.
Achievements
Backcross populations (BC4) from each of the recurrent parents and each of the aphid resistance donor parents were developed, and the pairs derived from the same recurrent parent were intercrossed to combine the resistance genes. Breeding lines homozygous for both aphid resistance genes have been selected. The improved Kirkhouse Benga and Wang Kae are also resistant to Striga.
Mr Patrick Attamah making crosses in the screen house.
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Phenotype of parent varieties and BC4F2 under artificial aphid infestation: IT97K-556-6, one of the donor varieties for aphid resistance (i); IT99K-573-2-1, the recurrent parent for Kirkhouse Benga, destroyed by aphids (ii); vigorous plant from a BC4 population derived from a cross between IT97K-556-6 and IT99K-573-2-1 (iii); the F1 population derived from a cross between the two parallel BC4 being advanced to the F2 generation where plants containing two copies of both aphid resistance genes (double homozygous- 1 in every 16 plants) can be selected for using molecular markers (iv).
Development of extra-early maturing, Striga and aphid resistance cowpea [Vigna unguiculata (L.) Walp] varieties
Mr Emmanuel Owusu
PhD student, Kwame Nkrumah University of Science and Technology (KNUST).
Supervisors: Professor Richard Akromah, KNUST; Dr Francis Kusi, CSIR-SARI; Dr Alexander Wireko Kena, KNUST.
Background
The timing of seed set in cowpea often coincides with terminal drought, a stress which can significantly reduce yield. Extra-early maturing varieties, which mature in 51-55 days, are better adapted than conventional ones to this stress, since they mature before the onset of terminal drought, and also avoid much of the damage caused by pests and diseases which affect the plants at the end of the cropping season.
Mr Emmanuel Owusu
Objectives
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To discover the mode of inheritance of earliness in the three early maturing lines Sanzi, Tobonaa and CB27.
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To identify sources of earliness controlled by different sets of gene(s).
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To introgress extra-earliness into the improved Striga and aphid resistant varieties Kirkhouse-Benga and Wang-Kae.
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To identify candidate gene(s) controlling earliness in cowpea.
Progress to date
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Polymorphisms for a number of molecular markers has been identified between Sanzi, Tobonaa and CB27 and the two improved varieties.
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A backcross breeding programme has been conducted featuring Sanzi, Tobonaa and CB27 as donors of extra-earliness and Kirkhouse Benga and Wang-Kae as the recipients; the progenies are currently at BC3F3. Promising selections have been subjected to a preliminary trial for yield potential, ensuring that they have retained resistance to both Striga and aphids. Among these, lines T11, T10 and T18 out-performed the checks in terms of maturity, seed size and grain yield, while T23, T5 and T4 were superior with respect to both earliness and yield.
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The genetic basis of the inheritance of earliness in Sanzi, Tobonaa and CB27 was deduced from segregation data in six basic generations. A generation mean analysis using the six basic generations indicated that gene action involved in the inheritance of days to first flower appearance and 95% pod maturity in Sanzi and Tobonaa was duplicate epistasis, whereas that of CB27 is complimentary epistasis.
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Sanzi seeds (i); field trials with CB27 (ii); advancing materials in 2019 in the greenhouse (iii).
Deployment of sources of cowpea root rot (Macrophomina phaseolina and Rhizoctonia solani) resistance to improve cowpea in Ghana
Mr Salim Lamini
PhD student, University of Ghana; Supervisors: Dr Francis Kusi, CSIR-SARI, Dr Eric W. Cornelius, University of Ghana, Dr Agyemang Danquah, West Africa Centre for Crop Improvement.
Background
Field surveys carried out in Northern Ghana during 2015 established that root rot, caused by one or both of the fungi Macrophomina phaseoli and Rhizoctonia solani, is an important constraint over cowpea productivity.
Mr Salim Lamini
Objectives
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To incorporate resistance to M. phaseolina into the cowpea variety Songotra.
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To determine the incidence and severity of M. phaseolina root rot across Northern Ghana through a survey.
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To identify and characterise M. phaseolina isolates from samples collected from cowpea growing locations in Northern Ghana.
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To identify cowpea genotypes with resistance to M. phaseolina.
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To determine the genetics of inheritance of M. phaseolina resistance in cowpea.
Achievements
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Cowpea plants showing symptoms of root rot infection were collected from sites in Northern, Upper East and Upper West Ghana. The pathogens were isolated and were identified on the basis of their morphology and genotype. The resulting strains were then back-inoculated into the susceptible cowpea variety Songotra. Re-isolated strains of M. phaseolina were used to screen a panel of 49 entries. A selection of three susceptible varieties (Songotra, Padituya and Zaayura) and seven resistant varieties (Suvita 2, Nhyira, Hewale, T2T4, AV2 3224, IT99K573-1-1 and Apagbaala) entries formed the basis of a diallele analysis. The resulting crosses were advanced to the F2 generation to determine the mode of inheritance of resistance. Resistance to M. phaseolina was shown to be conferred by two dominant complementary genes (both genes must be present in the dominant form, but not necessarily homozygous, for resistance to be expressed).
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The IT99K573-1-1 variety, used as the donor of Striga resistance to derive Wang Kae, was crossed and back-crossed to Songotra, reaching the BC4F3 generation in 2020. A selection of 76 lines resistant to M. phaseolina were field-tested in 2020. All the lines expressed resistance to the M. phaseolina root rot disease and Striga.
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A set of F7 recombinant inbred lines bred from the cross IT99K573-1-1 x Songotra was evaluated for their response to artificial inoculation with M. phaseolina, of which eight were selected for further evaluation. These lines were selected on the basis of their performance at F6 with respect to maturity time, seed coat and eye colour, and various podding traits.
Mr Lamini has successfully defended his PhD thesis and is awaiting his graduation.
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Microscopic Identification of root rot pathogens: M. phaseolina in culture (i); M. phaseolina scelorotia (x40 magnification; ii); R. solani in culture (iii); typical R. solani mycelia (x 40 magnification; iv); advancement of recombinant inbred lines (v).
Mode of inheritance and genetic relatedness of new sources of cowpea resistance found in Ghana
Ms Gloria Mensah
MSc in Biochemistry and Biotechnology, Kwame Nkrumah University of Science and Technology (KNUST).
Supervisors: Professor Antonia Tetteh, KNUST and Dr Francis Kusi, CSIR-SARI.
Project overview
A screen for seedling reaction to aphid infestation conducted at CSIR-SARI previously identified the five lines IT97K-556-6, KvX-295-2-124-99, 58-77, CB27 and SARC1-57-2 as potential donors of resistance. Our aim was to determine the mode of inheritance of the aphid resistance carried by CB27, KvX-295-2-124-99 and 58-77 and to define the allelic relationship of the genes responsible with those present in SARC1-57-2 and IT99K-556-6. F2:3 populations were developed from crosses between KvX-295-2-124-99, 58-77 and CB27 and the susceptible variety Apagbaala, with the resistant varieties SARC 1-57-2 and IT99K-556-6, and with one another. The populations were subjected to artificial aphid infestation and were also genotyped using a number of molecular markers. Progenies were scored as homozygous resistant, heterozygous or susceptible. A chi-squared goodness of fit test was used to analyse segregation ratios. The analysis demonstrated that the aphid resistance present in KvX-295-2-124-99, 58-77 and CB27 is controlled by a single dominant gene. The genes controlling aphid resistance in CB27, SARC1-57-2 and KvX-295-2-124-99 are allelic with one another but are non-allelic to the genes present in 58-77 and IT99K-556-6. The latter two varieties carry the same gene. For this work Ms Mensah was awarded her MSc in 2019.
Ms Gloria Mensah
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Young plants of IT97K-556-6, SARC-57-2 and Apagbaala showing symptoms of aphid damage (i); segregation of aphid resistance in F2:3 families derived from the cross KvX-295-2-124-99 x 58-77, indicating that these two varieties carry a different gene for resistance (ii); Ms Mensah tagging plants of her mapping population (iii).
Diversity of Striga gesnerioides on cowpea in Ghana
Mr Frederick Awuku
MSc Plant Breeding and Genetics, University of Ghana.
Supervisors: Professor Pangirayi Tongoona and Dr Agyemang Danqhah, University of Ghana, and Dr Francis Kusi, CSIR-SARI.
Project overview
Striga gesnerioides represents a major constraint over cowpea yield in northern Ghana but the identity and diversity of races has not been established. This project sought to characterize the distribution and diversity of S. gesnerioides in Ghana. The parasite was found to occur over a large area of the northern part of the country. Both purple and white flowered types are present, although the former predominate by about 3:1. The reaction of 27 cowpea varieties to eight S. gesnerioides populations sampled from three separate regions of northern Ghana revealed that some of the material was resistant to all of the populations, some was susceptible to all of the populations and some showed a differential response. The existence of the differential response implied the presence of more than one race of S. gesnerioides in Ghana. A genotypic survey of 27 samples of S. gesnerioides based on 73 newly developed PCR markers revealed two main clusters, supporting the suggestion that multiple strains of the parasite are present in Ghana. The identities of the races present in Ghana are likely SG3, SG2 and SG5.
Mr Frederick Awuku
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Map of Ghana indicating the Striga gesnerioides collection sites for this project (i); flower colour variation in S. gesnerioides sampled (ii-v).
PUBLICATIONS
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Owusu, E.Y., Kusi, F., Kena, A.W., Akromah, R., Awuku, F.J., Attamah, P. and Mensah, G., 2022. Generation mean analysis of the key earliness related traits in cowpea (Vigna unguiculata (L.) Walp). Scientific African 17, p.e01289.
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Owusu, E.Y., Kusi, F., Kena, A.W., Akromah, R., Attamah, P., Awuku, F.J., Mensah, G., Lamini, S. and Zakaria, M., 2022. Genetic control of earliness in cowpea (Vigna unguiculata (L) Walp). Heliyon 8, p.e09852.
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Tengey, T.K., Owusu, E.Y., Kusi, F., Mahama, G.Y., Awuku, F.J., Sei, E.K., Amoako, O.A. and Haruna, M., 2021. Grain yield and stability of selected early and medium duration cowpea in Ghana. African Journal of Plant Science 15: 71-81.
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Kusi, F., Nboyine, J.A., Attamah, P., Awuku, J.F., Sugri, I., Zakaria, M., Lamini, S., Mensah, G., Larweh, V., Owusu, R.K. and Agyare, R.Y., 2020. Stability of sources of resistance to cowpea aphid (Aphis craccivora Koch, Hemiptera: Aphididae) across major cowpea production zones in Ghana. International Journal of Agronomy 2020.
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Lamini, S., Cornelius, E.W., Kusi, F., Danquah, A., Attamah, P., Mukhtaru, Z., Awuku, J.F. and Mensah, G., 2020. Prevalence, incidence and severity of a new root rot disease of cowpea caused by Macrophomina phaseolina (Tassi) Goid in Northern Ghana. West African Journal of Applied Ecology 28: 140-154.
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Owusu, E.Y., Akromah, R., Denwar, N.N., Adjebeng-Danquah, J., Kusi, F. and Haruna, M., 2018. Inheritance of early maturity in some cowpea (Vigna unguiculata (L.) Walp.) genotypes under rain fed conditions in Northern Ghana. Advances in agriculture, 2018.
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Kusi, F., Padi, F.K., Obeng‐Ofori, D., Asante, S.K., Agyare, R.Y., Sugri, I., Timko, M.P., Koebner, R., Huynh, B.L., Santos, J.R. and Close, T.J., 2018. A novel aphid resistance locus in cowpea identified by combining SSR and SNP markers. Plant Breeding 137: 203-209.
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Kusi, F., 2014. Deployment of the cowpea aphid resistance gene for cowpea improvement in Ghana (Doctoral dissertation, University of Ghana).