Cowpea Breeding Research Articles

Transcriptome Analysis of Differentially Expressed Genes Associated with Salt Stress in Cowpea (Vigna unguiculata L.) during the Early Vegetative Stage.

Cowpea (Vigna unguiculata (L.), 2n = 22) is a tropical crop grown in arid and semiarid regions that is tolerant to abiotic stresses such as heat and drought. However, in these regions, salt in the soil is generally not eluted by rainwater, leading to salt stress for a variety of plant species. This study was conducted to identify genes related to salt stress using the comparative transcriptome analysis of cowpea germplasms with contrasting salt tolerance. Using the Illumina Novaseq 6000 platform, 1.1 billion high-quality short reads, with a total length of over 98.6 billion bp, were obtained from four cowpea germplasms. Of the differentially expressed genes identified for each salt tolerance type following RNA sequencing, 27 were shown to exhibit significant expression levels. These candidate genes were subsequently narrowed down using reference-sequencing analysis, and two salt stress-related genes (Vigun_02G076100 and Vigun_08G125100) with single-nucleotide polymorphism (SNP) variation were selected. Of the five SNPs identified in Vigun_02G076100, one that caused significant amino acid variation was identified, while all nucleotide variations in Vigun_08G125100 was classified as missing in the salt-resistant germplasms. The candidate genes and their variation, identified in this study provide, useful information for the development of molecular markers for cowpea breeding programs.

Genetic Diversity and Population Structure of Cowpea (Vigna unguiculata (L.) Walp.) Landraces from Portugal and Mozambique.

Cowpea (Vigna unguiculata (L.) Walp.) is currently a legume crop of minor importance in Europe but a highly relevant staple crop in Africa and the second most cultivated legume in Mozambique. In Portugal and Mozambique, cowpea's phenotypic and genetic variation has been maintained locally by farmers in some areas. We used the molecular markers SSR, SilicoDArT and SNP to analyze the genetic diversity and population structure of 97 cowpea accessions, mainly from Portugal (Southern Europe) and Mozambique (Southern Africa). As far as we know, this is the first time that the genetic variation and the relationship between cowpea landraces collected in Portugal with those originated in Mozambique is reported. Despite the shared historical past, the Portuguese landraces did not share a common genetic background with those from Mozambique, and two different gene pools were revealed. Knowledge of the genetic structure of cowpea landraces offers an opportunity for individual selection within landraces adapted to particular eco-physiological conditions and suggests the existence of a valuable gene pool for exploitation in future Portugal-PALOP (Portuguese-speaking African countries) cowpea breeding programs.

Phenotypic, genotypic and nutritional divergence in cowpea and implications for drought tolerance breeding: a review

Genetic diversity is crucial for crop improvement in any breeding program. Cowpea is an important indigenous grain vegetable legume crop. The crop has a significant potential to improve food and nutritional security in sub-Saharan Africa (SSA), and family income for resource poor famers. Cowpea is a source of proteins, vitamins (folate, thiamine and vitamin C), minerals (Fe, Zn, Mn and Ca) and amino acids such as lysine and tryptophan, hence, has a high potential for combating nutrient deficiencies. The SSA countries, including South Africa, have been experiencing many dry seasons, which have negatively affected agricultural production and productivity. Cowpea has a long taproot with the ability to grow in arid and semi-arid regions; however, lasting exposure to severe droughts will result in significant yield and grain quality reduction. There has been limited progress in drought tolerance research in cowpea due to the complexity of this trait, as it involves numerous genes, which in turn are affected by environmental conditions. It is therefore important to review research done on the nutritional, phenotypic and genotypic diversity of cowpea and the importance of diversity when breeding for complex quantitative traits such as drought tolerance and yield. The review will also outline the important omics tools used for drought tolerance breeding, cultivar development and as reference for future cowpea breeding.

Seleção de linhagens superiores de feijão-caupi derivadas de cultivares locais para a região semiárida brasileira

Abstract The objective of this work was to select superior cowpea lines derived from local cultivars for the semiarid region of southeastern Piauí, Brazil. A total of 38 genotypes (36 lines and two commercial cultivars) were evaluated in a randomized complete block design, with two replicates, in the municipality of Ipiranga do Piauí, in the state of Piauí. The following traits were evaluated: number of days to the onset of flowering, pod length, number of grains per pod, weight of 100 grains, commercial grain quality, and grain yield. Deviance analyzes were performed using the restricted maximum likelihood and best unbiased predictor approach, the parameters and genetic values were estimated, and simultaneous selection was carried out via the sum of ranks index. The likelihood ratio test showed a significant difference between the evaluated genotypes. Lines 36, 5, 24, 8, 2, 23, 29, 28, 34, 6, 19, 11, 7, and 20 are superior for the set of evaluated traits and, therefore, are the most promising to compose the advanced trial of the cowpea breeding program and to generate cultivars for family farmers in the semiarid region of southeastern Piauí.

Phenotypic Diversity of Cowpea (Vigna unguiculata L. Walp) Based on Shorter Cooking Time and Canning Quality Traits

Cowpea is a leguminous crop rich in protein. Despite its nutritional quality, the crop is underutilized due to its prolonged cooking time requiring energy to make it palatable. This study investigated the adaptation capacity, cooking time and canning quality of a panel of 94 accessions of cowpea obtained from the International Institute of Tropical Agriculture IITA, Ibadan and Rumukoro Market Port Harcourt Nigeria. Seeds were planted at the Department of Crop and Soil Science Research Farm and Allu Town, University of Port Harcourt, Nigeria. The experimental design was randomized complete block design (RCBD) in three replicates for three seasons (early wet, late wet and dry season). Agronomic Parameters such as plant height, number of leaves, number of branches, leave length, leave width, and the flowering date was collected at two weekly intervals after weeks of planting. The cooking evaluation was carried out using a digital cooker (Tower Product), while canning quality was evaluated using a cost-effective sealer. Results obtained showed that cowpea adapted to the three seasons with optimal performance observed in the late wet season. The cooking results showed that TVU-2, TVU-8, TVU-9, TVU-13, TVU, 21, TVU29, TVU-36, TUV-38, iron white, akara bean, iron brown and honey bean had short cooking time while TVU-2, TVU-13, TVU-26, TVU-37, TVU-38, TVU-45, TVU-50 and TVU-51 had good canning quality. It is recommended that the selected accessions for better agronomic and culinary quality traits can be used for cowpea breeding programmes.

Breeding implications of nodulation performance and root structure under natural inoculation for soil fertility enhancement and sustainable cowpea production

Nitrogen deficiency is the most limiting abiotic stress factor affecting the grain yield of cowpea (Vigna unguiculata L.) in sub-Saharan Africa (SSA) countries. Breeding for high-yielding potential in association with high nitrogen fixation performance is the principal objective of cowpea breeding programs to improve both the productivity and production of this orphan crop in the region. Therefore, the present study was undertaken to determine the diversity of genotypes for nodulation capacity in two environments and to understand the root architecture and morphology of genotypes as well as grain yield and yield-related traits in 324 cowpea genotypes. The experiment was conducted in two different environments during the 2017 cropping season. The experiments were laid out in 18 × 18 simple lattice design. Grain yield exhibited highly significant and positive genotypic correlations with stem diameter, basal root length of 1st whorls, basal root branching density, taproot length and adventitious root length, demonstrating that selection of cowpea genotypes based on these traits could be effective to capitalize on grain yield under low nitrogen conditions. Days to flowering, days to maturity, stem diameter, 1st whorl angle, basal root length of 1st whorls, basal root branching density, taproot length, adventitious root diameter and adventitious root length had significant and positive genotypic correlations with days to maturity. The first ten principal components (PC) explained 65.13% of the total variation. Stem diameter, taproot width, and taproot length traits were important contributors to the variability in the first PC. The highest inter-cluster distance (D2) was recorded between clusters III and IV. However, clusters II and V recorded the minimum inter-cluster distance (78.96 units). The range of intra-cluster distance was 24.22–5,112.92 units, indicating that the high genetic distance displayed within and between clusters has to be exploited via crossing and selecting the most divergent parents for future cowpea improvement. Five clusters of cowpea genotypes were evident, and within the clusters, the genotypes had good nodulation potential with high grain yield traits, which could significantly contribute to SSA food and nutritional security. Moreover, it can contribute to resilience and improve crop production and sustainability under marginal environmental conditions.

Estimates of genotypic and phenotypic variance, heritability, and genetic advance of horticultural traits in developed crosses of cowpea (Vigna unguiculata [L.] Walp).

Cowpea, in addition to being a food and feed crop, plays a key role in sustainable farming. The present study’s goal is to develop new high-yielding cowpea varieties. A Field experiment was carried out across 3 summer seasons and the breeding program included 28 distinct cowpea varieties, out of which five potential parents were selected for this investigation. Local cultivars, i.e., Cream 7 ‘Cr7’, Dokki 331 ‘D331’, Commercial 1 ‘Com1’, and introduced cultivars, i.e., Colossus ‘Col’ and Asian Introduction ‘AI’ were utilized to produce six crosses in two generations apart; F1 and F2: Col x AI, Col x Com1, Cr7 x AI, Cr7 x Com1, D331 x AI, and D331 x Com1. ‘AI’ and ‘Com1’ were superior in pod length, pod diameter, number of seeds/pod and seeds weight/pod, whereas ‘Col’, ‘Cr7’ and ‘D331’ were superior in seeds yield/plant, number of pods/plant and the least number of aborted ovules/pod. The genotypes/crosses showed greater genotypic variance (GV) than phenotypic variance (PV) for number of pods/plant, pod length, number of seeds/pod, number of aborted ovules/pod, fresh pod weight, seeds weight/pod, and seeds yield/plant. All studied variables showed high heritability (H%) in genotypes/crosses, despite the exception of seeds weight/pod, which ranged from 29.14 in ‘D331’ to 83.7 in F2 of Col x Com1. F2 plants and their parents’ genotypes showed greater H%. Cr7 x AI developed the most H%, 99.04% for number of pods/plant. D331 x Com1 and Cr7 x AI exhibited moderate H% for fresh pod weight in F1, but all other crosses had high H%. F1 and F2 crosses yielded moderate to high GCV and PCV for number of seeds/pod. Variations in parental genotypes and crossings reflect genetic diversity and the possibility of selection. Crossing with ‘AI,’ and ‘Com1’ genotypes enhanced the performance of the other varieties, ‘Col’, ‘D331’ and ‘Cr7’. Cr7 x Com1 and D331 x AI were selected as the most promising crosses for cowpea breeding programs.

Cowpea speed breeding using regulated growth chamber conditions and seeds of oven-dried immature pods potentially accommodates eight generations per year

BackgroundCowpea is a dryland crop with potential to improve food security in sub-Saharan Africa, where it is mostly produced and consumed. Contemporary plant improvement technologies, including genome editing, marker-assisted selection, and optimized transformation protocols, are being deployed to improve cowpea characteristics. Integrating speed breeding with these technologies would accelerate genetic gain in cowpea breeding. There are established speed breeding protocols for other important legumes, such as soybean, peanut, and chickpea, but none has been previously reported for cowpea.ResultsWith the aid of regulated growth conditions in two different chamber types, as well as the cultivation of new plant generations from seeds of oven-dried immature pods, we developed and validated, for the first time, an efficient speed breeding protocol that accommodates approximately seven to eight breeding generations per year for 3 cowpea genotypes. The 3 cowpea genotypes were evaluated under controlled growth conditions in light-emitting diode and metal halide lamp chambers to determine the effect of CO2 supplementation on flowering and maturation durations, optimum conditions for plant growth, cross pollination, and pod development. Elevated CO2 concentration had no influence on either flowering time or pod development. Adequate temperature, relative humidity and light intensity improved plant development and the rate of successful hand pollination, and cultivating seeds of 11-day-old immature pods oven-dried at 39 °C for 2 days resulted in at least a 62% reduction in the time between pollination and sowing of the next plant generation. The plants cultivated from seeds of the oven-dried immature pods showed no defect at any stage of development.ConclusionsUsing the speed breeding protocol developed in this study, cowpea breeding cycles can be increased from the traditional one cycle per year in the field to as many as 8 generations per year in regulated growth chamber conditions. This protocol has no special technical requirements; hence, it can be implemented in any standard growth chamber. This would fast-track development, testing, validation, and utilization of improved cowpea cultivars.

Resistance to Callosobruchus maculatus among cowpea (Vigna unguiculata (L.) Walp) genotypes

ABSTRACT Callosobruchus maculatus is an important field-to-store pest that causes close to 100% losses in stored produce. This study aimed at assessing the resistance of cowpea genotypes to C. maculatus infestation. Thirteen cowpea advanced breeding lines pre-selected on the basis of their high grain yield, and three released varieties (Padi-tuya, Kirkhouse Benga and Wangkae) were evaluated in a no-choice experiment. The experiment was laid out in a completely randomized design with four replications under laboratory conditions. Data were collected on mean number of eggs per seed (MEPS), days to first emergence (DFE), adult bruchid emergence (ABE), percentage weight loss (PWL), percentage seed damage (PSD) and median development period (MDP). Dobie’s susceptibility index (DSI) was computed and used to classify the genotypes as resistant or susceptible. Significant differences were found among the genotypes for the measured traits, except for DFE and MDP. IT13K-1070-2 had the lowest MEPS, ABE, PWL and PSD. C. maculatus, with high ABE, developed best on Kirkhouse Benga and Wangkae. Wangkae had 100% seed damage at the end of the experiment. Based on the DSI score, IT13K-1070-2 was found to be moderately resistant; the rest of the genotypes were susceptible. Among the susceptible genotypes, IT10K-817-3, IT07K-303-1, SARI-2-50-80, SARI-3-11-100, IT10K-837-1, IT13K-1424-12 and SARVX-09-004 had PWL of less than 16%, indicating tolerance to bruchid infestation. DSI was significantly and positively correlated with ABE (r = 0.81), PSD (r = 0.93) and PWL (r = 0.79). DSI had a significant negative correlation with the final seed weight (r = −0.83). IT13K-1070-2 could serve as a useful source of resistance to the cowpea bruchid in cowpea breeding programs or released as a variety for cultivation.

Assessing high-yielding cowpea varieties for bacterial blight resistance in Bangladesh: A step towards an environment-friendly and sustainable solution

Cowpea is well-known worldwide for its high protein content, versatile use, and adaptability. However, it is devastatingly affected by bacterial blight disease caused by Xanthomonas axonopodis pv. vignicola (Xav). The present study was designed to assess ten high-yielding cowpea varieties for bacterial blight resistance in two contrasting cropping seasons in Bangladesh. The varieties were evaluated using seed and stem inoculation with Xav bacteria, followed by phenotypic and molecular characterisation. The varieties were morphologically assessed using nine disease-related qualitative and quantitative traits, and genetic variations were investigated through nine SSR markers. Disease development varied significantly (P = 0.05) among the varieties. Substantially higher disease incidence was observed in the Kharif season compared to the Rabi season. Felon local, Dark Green-28, and Dark Green-1028 varieties were resistant in both seasons. On the other hand, BARI Felon-1 was highly susceptible to susceptible in both seasons as infections were over 50%. Moreover, plant height, leaf area, branch number, and leaf number significantly differed among the varieties. Besides, in the molecular study, polymorphism information content and Nei’s gene diversity were detected as 0.3658 and 0.4089, respectively. Kegornatki showed the highest genetic variation vs Dark Green-1028. The UPGMA dendrogram segregated the ten cowpea varieties into two main clusters. This study revealed that three high-yielding varieties, viz., Dark Green-28, Dark green 1028, and Felon local, were resistant to bacterial blight and showed better performance in morpho-molecular characterisation. Therefore, these varieties can be integrated into future cowpea breeding programmes to develop cultivars that can control the high pressures of Xav.

SEASONAL RESPONSES OF FLOWERING AND POD SETTING IN COWPEA (Vigna unguiculata L. Walp)

Seven varieties of cowpea, Vigna unguiculata L. Walp were studied in two field trials (the wet and dry seasons) in the 2021 cropping season in Agbor, South-South geopolitical zone of Nigeria, were laid out in a complete randomized block design (CRBD) with seven replications for seasonal responses of flowering and pod setting. The dry season crops were manually watered twice daily while the wet season crops were rain-fed. The study recorded that most of the cowpea genotypes grown in the wet season showed photoperiod sensitivity, flowering between 46.36 and 56.43 DAP with mean of 54.97 + 6.98. Pod setting was similar across genotypes but the number (9.64 + 8.29), while length of pods varied (14.66 + 2.83) as noted from field observations. Furthermore, Seeds per pod was not significant among varieties of the wet season but they were significant and among those of the dry season (9.37 + 5.17). Genotypes which flowered earlier produced higher number of pods per plant and gave better yield such as IT06K-149-1, IT98K-128-3, IT95K1072-57 and IT98K-506-1 with grain filling of 205.58, 186.3, 183.53 and 775.99 mean seeds respectively were consequently recommended for hybridization in cowpea breeding programmes in south-south Nigeria.

Inheritance of resistance to three endemic viral diseases of cowpea in Nigeria

ABSTRACT Mosaic diseases, caused by bean common mosaic virus-blackeye cowpea mosaic strain (BCMV-BlCM), southern bean mosaic virus (SBMV), and cucumber mosaic virus (CMV), hamper the productivity of cowpea (Vigna unguiculata (L.) Walp.). Under single or mixed infections, these endemic viruses significantly reduce cowpea yield in sub-Saharan Africa. Planting resistant varieties is the most effective control method. Knowledge of the mode of inheritance of viral resistance is crucial in developing resistant varieties. Inheritance of resistance to BCMV-BlCM, SBMV, and CMV was investigated in two improved cowpea breeding lines. For BCMV-BICM, crosses were made between resistant IT97K-1042-3 (female) and susceptible IT99K-1060 (male); for SBMV, between resistant IT98K-1092-1 (male) and susceptible IT99K-1060 (female); and for CMV, between tolerant IT98K-1092-1 (female) and susceptible IT99K-573-1-1 (male). The F1 progenies were advanced to F2, and some F1 plants were backcrossed to the two parental lines. Reciprocal crosses were made and the 7-day-old seedlings of P1, P2, F1, F2, BCP1, and BCP2 were phenotyped by mechanical inoculation with BCMV-BlCM, SBMV, and CMV under screenhouse conditions. Data on disease incidence and severity were taken at weekly intervals for 5-week post-inoculation. Virus infections were confirmed via antigen-coated plate enzyme-linked immunosorbent assay or reverse transcription-polymerase chain reaction. Chi-square analysis of the genetic segregation indicated that a recessive gene pair in IT97K-1042-3 controlled the inheritance of resistance to BCMV-BlCM. Duplicate dominant genes conditioned the resistance to SBMV and tolerance to CMV in IT98K-1092-1. The backcrosses confirmed the monogenic and digenic inheritance patterns, whereas reciprocal crosses indicated absence of cytoplasmic effects.

Lower doses of sodium azide and methyl methanesulphonate improved yield and pigment contents in vegetable cowpea [Vigna unguiculata (L.) Walp.]

Cowpea, often categorized as an orphan crop, is an essential member of the Fabaceae family and is recognised as a primary crop by Food and Agriculture organisation. It is adapted to a wide range of dry ecologies; however, its yield is low compared to other grain legumes. Considering its low yielding potential, a traditional cowpea variety Gomati VU-89 was treated with lower (0.01%) and higher (0.04%) sodium azide (SA) and methyl methanesulphonate (MMS) doses. An extensive phenotyping selection on traits such as plant height, days to flowering, branches, pods, seeds, and seed yield, resulted in the isolation of two high yielding putative mutants. Among the mutagen doses, the highest increase in mean seed yield was recorded in 0.02% SA (65.00 gm) and 0.02% MMS (65.07 gm). One-way analysis of variance and post hoc Duncan's multiple range test showed that mutagenized populations deviated significantly from the control population. Correlation analysis showed seed weight and plant height possesses a strong positive correlation with yield; therefore, these characters could be used in indirect selection for yield improvement. Hierarchical cluster analysis revealed mutagen-induced divergence by classifying five populations into four groups, each with 1–2 clusters. Principal component analysis showed that two principal components explained more than 95% of the total variation in mutagen treated populations. Seeds per pod and pod length showed maximum positive loading on PC1 in MMS (0.359) and SA (0.371) treated populations, respectively. In contrast, days to flowering revealed maximum positive loading on PC2 in MMS (0.707) and SA (0.635) treated populations. Putative mutants showed high yielding potential compared to the control plants and could be employed in future cowpea breeding programs for genetic enrichment of existing varieties.

Yield variation and aphid scoring of different cowpea (Vigna unguiculata) genotypes across the environment

Producing improved legume forages may contribute to the improvement of the quality supply of the livestock feeding system in Ethiopia. Dry matter and seed yield evaluation and aphid infestation scoring of cowpea genotypes were undertaken for three production seasons (2018-2019). The treatment of five cowpea accessions (ILRI_9333, ILRI_9334, ILRI_11114, ILRI_12668, and ILRI_12713) and one recently released variety as a standard check (Temesgen) at three locations (Arba Minch Agricultural Research Center (AMARC), Bonga Agricultural Research Center (BARC) and Hawassa Agricultural Research Center (HARC) was laid out at the field in a randomized complete block design with three replications. Growth, yield, and aphid scoring parameters were collected to present the comparison of genotypes. Vine length and branch number of ILRI_3334 followed by ILRI_12173 was significantly taller in all locations than the standard check and other genotypes in the test. Dry matter yield production was significantly (P<0.05) higher for ILRI_12713 (8.87 t/ha) followed by ILRI_9334 (8.44 t/ha) and ILRI_11114 (8.4 t/ha) while in seed yield variety ILRI_11114>ILRI_12668>ILRI_12713 than Temegen and others in the experiment. Aphid infestation in the cowpea field significantly influenced dry matter yield and seed yield. Dry matter yield was positively correlated with branch number and vine length. Seed yield was positively and significantly (P= 0.047 and 0.015) correlated with seed per pod and harvest index. Hence, ILRI_12713, ILRI_9334, and ILRI_11114 are to be considered for further cowpea breeding programs for dry matter and seed yield under aphid-infested conditions. Quality of the materials under irrigated and other agronomic conditions might be the future assignment.

Evaluation of Cowpea Morpho-physiological and Yield Responses to Vegetative and Pre-Anthesis Water-Deficit Stress Tolerance under Greenhouse Conditions

Cowpea production is severely hindered by water scarcity; thus, understanding morpho-physiological response mechanisms of known drought-tolerant cultivars under water-deficit stress is critical to identify and establish representative yield-related traits of climate-hardy cowpeas. To determine cowpea genotypic variability to drought-tolerance, seventeen days-post sowing (DPS) greenhouse plants were subjected to 14-days drought stress without watering, then watered every 10-days at 25%, 50%, and 75% field capacity (FC) until maturity in two-trial experiments. Controls were well-watered at 100% FC every 3-days. Drought stress data were collected on plant height, stem diameter, chlorophyll content and terminal leaflet expansion rate. At maturity, 83 to 119 DPS, pod number, shoot and root biomass, and seed yield per plant were recorded. Data were combined and analyzed using analysis of variance. Drought tolerance was evaluated by percent change in performance and stress tolerance indexes. Drought stress in both trials impacted phenotypic expression. Plant height declined by 74%, stem diameter 18.2%, chlorophyll content, 47.6% terminal leaf length 83.2%, and width 85.2%. Pods per plant were reduced by 73% and seed yield by 98.8%. The estimated correlation between morpho-physiological and other yield-related traits of drought-tolerance indices verified that TVu 11987, LOBIA-I-SEFADE, and TVu 7362 were drought tolerant along with confirmed tolerant commercial cultivars California Blackeye No.5, Big Boy, and  Lady. These cultivars exhibited different stress-coping strategies of low water requirements and growth performance to yield reduction. Overall, the genotypic performance recorded as drought-tolerant characteristics may be recommended as potential screening factors for donor cultivar traits in cowpea breeding programs.

IITA\u2019s genebank, cowpea diversity on farms, and farmers\u2019 welfare in Nigeria

BackgroundCowpea or black-eyed pea (Vigna unguiculata L.) is one of the preferred food crops in Nigeria, as expressed in land area and production. The popularity of the crop is in part related to the successful development and adoption of improved cowpea varieties. Although the genebank of the International Institute of Tropical Agriculture (IITA) has contributed to cowpea conservation and improvement efforts by breeding programs internationally and in Nigeria, few studies have attempted to link the genebank to the management of cowpea genetic resources (CGRs) on farms. This study explores the linkage between IITA’s genebank and cowpea variety diversity on farms and other measures of farmers’ welfare in Nigeria.MethodsA multistage stratified sampling was used to select the sample households. A cross-sectional household survey was conducted to collect data from 1524 cowpea-producing households. In addition, “Helium”, a multi-platform pedigree visualization tool with phenotype display was used to gather information about improved cowpea breeding lines and their pedigrees. For data analysis, ecological indices of spatial diversity were employed, and a conditional recursive mixed-process model and a multinomial endogenous treatment effect model were developed.ResultsWe found that growing an improved variety with genebank ancestry is not significantly associated with lower spatial diversity among cowpea varieties. While they may introduce new traits through ancestry, improved varieties do not displace other cowpea varieties or landraces. We also found that genebank ancestry is positively and significantly associated with cowpea yield and farmers’ welfare.ConclusionsThese findings show additional benefits from IITA’s genebank in Nigeria and that adoption of improved varieties with genebank ancestry does not contribute to the erosion of CGRs on smallholder farms in Nigeria. Policymakers and practitioners should consider these findings when analyzing the benefits of conserving crop genetic diversity in genebanks and on farms.

Genetically related genotypes of cowpea present similar bacterial community in the rhizosphere

Plant breeding reduces the genetic diversity of plants and could influence the composition, structure, and diversity of the rhizosphere microbiome, selecting more homogeneous and specialized microbes. In this study, we used 16S rRNA sequencing to assess the bacterial community in the rhizosphere of different lines and modern cowpea cultivars, to investigate the effect of cowpea breeding on bacterial community assembly. Thus, two African lines (IT85F-2687 and IT82D-60) and two Brazilian cultivars (BRS-Guariba and BRS-Tumucumaque) of cowpea were assessed to verify if the generation advance and genetic breeding influence the bacterial community in the rhizosphere. No significant differences were found in the structure, richness, and diversity of bacterial community structure between the rhizosphere of the different cowpea genotypes, and only slight differences were found at the OTU level. The complexity of the co-occurrence network decreased from African lines to Brazilian cultivars. Regarding functional prediction, the core functions were significantly altered according to the genotypes. In general, African lines presented a more abundance of groups related to chemoheterotrophy, while the rhizosphere of the modern cultivars decreased functions related to cellulolysis. This study showed that the genetic breeding process affects the dynamics of the rhizosphere community, decreasing the complexity of interaction in one cultivar. As these cowpea genotypes are genetically related, it could suggest a new hypothesis of how genetic breeding of similar genotypes could influence the rhizosphere microbiome.

Morphological and molecular characterization of cowpea (Vigna unguiculata L. Walp.) genotypes

Cowpea [Vigna unguiculata (L.) Walp.], is a legume and one of the most ancient crops known to man and grown in tropical and subtropical regions. Cowpea seeds have a high nutritional value containing high amount of protein (20-25%). Despite of its importance, the utilization of genetic diversity and germplasm characterization in cowpea breeding program has not been fully exploited. Therefore, twelve morphological characters and six polymorphic microsatellite/simple sequence repeat (SSRs) markers were used to analyze genetic diversity in thirty-eight cowpea genotypes. The dendrogram was constructed using UPGMA algorithm and Gower?s dissimilarity values (ranged from 0.0601 to 0.5589) derived from twelve morphological characters. It was grouped in seven clusters showing the most diverse genotypes were CGD 1246 and CGD 1311 (Gower?s distance: 0.5589) and the most similar genotypes were GC 1501 and GC 1601 (Gower?s distance: 0.0601). In molecular characterization, a total of 14 amplicons were detected with a ranged from two to three with an average 2.33 alleles per loci. The mean values of polymorphic information content (PIC) and heterozygosity was 0.319 and 0.399, respectively which are measures of the efficiency of markers for studying polymorphism level available in the cowpea genotypes. Total 224 amplicons were considered for to derive Jaccard?s similarity matrix for the construction of dendrogram (having six clusters) and 2-D PCA (Principal Component Analysis) plot. The morphological characters and SSR markers can be used in diversity analysis and characterization of cowpea genotypes. The per se performing genotypes for individual character can be exploited in population/genotype development of cowpea for the improvement of that particular character. This will provide information to plant breeders for selection of parents to develop populations in cowpea breeding programs.

Phenotyping cowpea for seedling root architecture reveals root phenes important for breeding phosphorus efficient varieties

AbstractCowpea (Vigna unguiculata L. Walp.) is a key climate‐resilient legume for food security, especially in sub‐Saharan Africa. Cowpea yields are limited by edaphic stresses including drought and low phosphorus (P) availability. Identifying genotypes with advantageous root phenotypes can facilitate breeding for improved yield in marginal environments. We evaluated 50 elite genotypes from African and U.S. sources for seedling root architecture and root hair length and density. Significant genotypic variation was detected for all phenes, and high heritability was observed for architectural phenotypes including primary root length (77%), basal root number (72%), and taproot branching density (67%). Moderate heritability was detected for root hair length and density among different root classes (34 to 63%), which were positively associated with each other. Principal component analysis identified three clusters, primarily defined by seed dimension and seedling root architecture. Genotypes were identified with longer root hairs (TVu‐7778, Vita7, and Sanzi) and longer taproots (IT96D‐610, IT98K‐111‐1, and IT97K‐499‐35), as potential parents. Root phenotypes, grain, and fodder yield were assessed on a subset of 20 genotypes under contrasting P availability in the field. Some seedling root phenotypes were significantly related to mature plant dry fodder weight (taproot hair density) and to grain yield (lateral root hair density) under low P. Root hairs are positively related to plant productivity under low P. We suggest selection for longer primary roots, as more basal and lateral root roots may be beneficial for cowpea in drought and low P environments. These findings suggest seedling root phenotypes can support cowpea breeding for suboptimal environments.

Dissecting the salt tolerance potential of cowpea genotypes based on morpho‐physiology and yield‐related attributes

AbstractHigh salinity is a critical environmental menace hampering crop growth and productivity worldwide. Therefore, dissecting the salt tolerance potentials and identifying resilient genotypes are crucial to secure sustainable crop production. In this study, we explored the salt resistance potentials of three advanced cowpea lines including one check variety exposed to different salinity levels (0, 50 and 100 mM of natural saline water) by quantifying their growth, physiology and yield‐related attributes. Our results implied that salt‐stress resulted in a significant reduction in the morphological, physiological and yield attributes at both 40 and 60 days after sowing when compared to non‐stress plants. Interestingly, we noticed that one of the latest cowpea genotypes (BU‐C‐Acc‐3) sustained better performances in terms of growth, physiology and yield‐related characters at both 50 and 100 mM salt treatments, while other genotypes exhibited varying levels of salt responses. Further, a multivariate analysis showcased that genotype ‘BU‐C‐Acc‐3’ acquired a combination of physiological and yield contributing responses that ultimately induced a higher level of resistance and grain yield. Collectively, our study offers some contrasting genotypes which could be incorporated in current cowpea breeding programmes to improve grain yield and salt tolerance using conventional as well as molecular breeding tools.