These authors contributed equally. SUMMARYCowpea (Vigna unguiculata L. Walp.) is a legume crop that is resilient to hot and drought-prone climates, and a primary source of protein in sub-Saharan Africa and other parts of the developing world. However, genome resources for cowpea have lagged behind most other major crops. Here we describe foundational genome resources and their application to the analysis of germplasm currently in use in West African breeding programs. Resources developed from the African cultivar IT97K-499-35 include a whole-genome shotgun (WGS) assembly, a bacterial artificial chromosome (BAC) physical map, and assembled sequences from 4355 BACs. These resources and WGS sequences of an additional 36 diverse cowpea accessions supported the development of a genotyping assay for 51 128 SNPs, which was then applied to five bi-parental RIL populations to produce a consensus genetic map containing 37 372 SNPs. This genetic map enabled the anchoring of 100 Mb of WGS and 420 Mb of BAC sequences, an exploration of genetic diversity along each linkage group, and clarification of macrosynteny between cowpea and common bean. The SNP assay enabled a diversity analysis of materials from West African breeding programs. Two major subpopulations exist within those materials, one of which has significant parentage from South and East Africa and more diversity. There are genomic regions of high differentiation between subpopulations, one of which coincides with a cluster of nodulin genes. The new resources and knowledge help to define goals and accelerate the breeding of improved varieties to address food security issues related to limited-input small-holder farming and climate stress.

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These authors contributed equally. SUMMARYCowpea (Vigna unguiculata L. Walp.) is a legume crop that is resilient to hot and drought-prone climates, and a primary source of protein in sub-Saharan Africa and other parts of the developing world. However, genome resources for cowpea have lagged behind most other major crops. Here we describe foundational genome resources and their application to the analysis of germplasm currently in use in West African breeding programs. Resources developed from the African cultivar IT97K-499-35 include a whole-genome shotgun (WGS) assembly, a bacterial artificial chromosome (BAC) physical map, and assembled sequences from 4355 BACs. These resources and WGS sequences of an additional 36 diverse cowpea accessions supported the development of a genotyping assay for 51 128 SNPs, which was then applied to five bi-parental RIL populations to produce a consensus genetic map containing 37 372 SNPs. This genetic map enabled the anchoring of 100 Mb of WGS and 420 Mb of BAC sequences, an exploration of genetic diversity along each linkage group, and clarification of macrosynteny between cowpea and common bean. The SNP assay enabled a diversity analysis of materials from West African breeding programs. Two major subpopulations exist within those materials, one of which has significant parentage from South and East Africa and more diversity. There are genomic regions of high differentiation between subpopulations, one of which coincides with a cluster of nodulin genes. The new resources and knowledge help to define goals and accelerate the breeding of improved varieties to address food security issues related to limited-input small-holder farming and climate stress.

Two parasitic weeds, Striga gesnerioides (Willd.) Vatke and Alectra vogelii Benth., cause heavy yield losses in cowpea (Vigna unguiculata (L.) Walp.) throughout the semiarid regions of sub‐Saharan Africa. Several sources of resistance have been identified, including B 301, a landrace from Botswana that has shown complete resistance to both striga and alectra. Striga resistance in B 301 is conditioned by a single dominant gene. Our objective was to determine the inheritance of alectra resistance. B 301 was crossed to three susceptible cultivars (IT84S‐2246‐4, SUVITA‐2, and IT82D‐849) and F1, F2, and backcross seeds were obtained. The reaction of parental, F1, F2, and backcross plants to alectra infestation was evaluated. Test populations were planted in plastic pots of 13 cm diani. filled with a mixture of sand and soil and ≈800 alectra seeds. The roots of each plant were examined for alectra attachment 10 wk after planting, and the number of resistant and susceptible plants in each population were recorded. All plants of B 301 and backcrosses to B 301 were completely free from alectra. All plants of IT84S‐2246‐4, SUVITA‐2, and IT82D‐849 were susceptible. All F2 populations segregated 15 resistant : 1 susceptible, and backcrosses to the susceptible parents segregated 3 resistant : 1 susceptible indicating duplicate dominant gene inheritance. We propose the gene symbols Rav1 and Rav2 (resistance to Alectra vogelii) for this trait.

The continued improvement in the yield of cowpea for the semi-arid regions where it is a dominant crop will record rapid progress if the genetic basis for yield under different moisture regimes is better understood. This study investigated the genetic combining abilities and heterosis for grain yield, yield components, flowering and biomass production among diallel hybrids derived from nine cowpea genotypes. Results showed that moisture stress significantly reduced grain yield, biomass production, and number of pods per plant. Only for grain yield was a significant interaction observed for moisture regimes. Genetic control for grain size, number of seeds per pod and days to flowering was dominated by additive genetic effects. For grain yield, both additive and non-additive genetic effects were dominant. The genetic control of yield under the two soil moisture conditions indicated that grain yield improvement will be more challenging for drought prone regions. Nonetheless, careful selection of genotypes that have complementary but different alleles for yield under different soil moisture conditions might permit yield improvement through recurrent selection. This study has identified parental lines, developed populations, and provided a breeding strategy for developing cowpea cultivars with higher grain yield for Guinea and Sudan savannah regions of West Africa.