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Background Cowpea, Vigna unguiculata, is an important food legume in the tropics and subtropics. However, cowpea is a complex species with more than 10 subspecies which can hybridize and produce intermediate progenies. Partly because of the complex organization of the cowpea gene pool and the lack of adequate markers for these infraspecific units, cowpea breeders are not using the wild part of the cowpea gene pool. Methods Here, we report the molecular characterization of 34 representative accessions with 61 SSR markers from coding regions. Results If SSR failed to separate the closest groups, i.e. subsp. alba, subsp. tenuis and the perennial groups from subsp. unguiculata, a combination of few SSR markers can properly identify the main cowpea subspecies. Regarding the infraspecific phylogeny of cowpea, SSR markers confirm the special status of the annual subsp. unguiculata versus the different perennial subspecies. It confirms that subsp. protracta looks like the oldest subspecies, making the origin of the species in southern Africa likely. However, it unites in a single group, clearly separated from subsp. unguiculata, all the taxa of hybrid origin, i.e. subsp. alba, subsp. tenuis, subsp. pubescens and the BWA group of subsp. unguiculata. Conclusion Although a limited number of markers was tested considering that several hundred of cowpea SSR are available, the present work shows that SSR markers can be used for molecular characterization of cowpea subspecies and can be very helpful for understanding its complex evolutionnary history.

Increasing sorghum production per unit area in the farmer’s field by developing high yielding tannin-free and grain mold tolerant varieties in Senegal is the goal of the present study. Line × tester mating design was used to cross eleven tannin-free non-photoperiodic male fertile sorghum varieties with two male-sterile A-lines to produce 22 F1 hybrids. These hybrids along with the thirteen parents and one grain mold resistant hybrid check were evaluated under natural grain mold infestation in two contrasted sites using a 6 × 6 lattice design with three replications. Results on combining ability suggested that additive gene actions were important in the control of grain mold resistance while non-additive gene actions were preponderant in the inheritance of grain yield. The parental lines F2-20, Macia, Faourou, and Dorado were the best general combiner for grain mold resistance. Of these, Dorado was identified as the best combiner for yield and yield components. Additionally, the hybrid CE310-31A × Sureno was identified as the best hybrids combination for yield, yield components and grain mold resistance. Furthermore, the hybrid crosses CE310-31A × F2-20, CE310-31A × Sureno and AVG-1 × Dorado showed the best mid-parent heterosis for grain yield and resistance to grain mold. Moreover, based on their combining ability and heterosis, seven hybrids were identified for their resistance to grain mold and high yielding. These hybrids could be tested in multi-location trials for a subsequent release.

Cowpea (Vigna unguiculata (L.)) is an important crop for food security in Senegal; therefore, understanding the genetic diversity of local germplasm is relevant for crop improvement and genetic maintenance in the era of climate change. For this purpose, 15 microsatellite markers were used to estimate the genetic diversity of Senegalese cowpea germplasm, including 671 accessions grown in eight regions and 66 wild relatives and intermediate forms (weedy). For the cultivated, the main expected heterozygosity (mHe) ranged between 0.317 (Fatick) and 0.439 (South). A narrow genetic variation between accessions from the different regions was observed with genetic similarity ranging from 0.861 to 0.965 and genetic differentiation indices (Fst) between 0.018 and 0.100. The accessions from southern Senegal (Kédougou, Sédhiou, and Kolda regions) are more diverse than the others. However, the accessions from the North (Saint-Louis) are genetically different from other regions. The diversity analysis in wild relatives from Senegal, which had never been performed before, revealed that the wild/weedy forms remain more diverse than the cultivated with genetic diversity values (He) of 0.389 and 0.480, respectively. STRUCTURE software divided the Senegalese germplasm into five subpopulations. Three of them (i, ii, and iii) included only cultivated accessions from several regions, one (v) mainly from Saint-Louis, and one (iv) the wild/weedy with some cultivated accessions. Our results support the hypothesis that Vigna unguiculata var. spontanea is the wild progenitor of cowpea. The accessions from the South, the northern recession accessions, and the wild/weedy could serve as sources of new genes for the genetic improvement of cowpea in Senegal.

SUMMARYDrought is a major constraint on plant productivity globally. Sorghum (Sorghum bicolor) landraces have evolved in drought-prone regions, but the genetics of their adaptation is not yet understood. Loci underlying stay-green post-flowering drought tolerance (Stg), have been identified in a temperate breeding line, but their role in drought adaptation of tropical sorghum is to be elucidated.We phenotyped 590 diverse sorghum accessions from West Africa under field-based managed drought stress, pre-flowering (WS1) and post-flowering (WS2) over several years and conducted genome-wide association studies (GWAS).Broad-sense heritability for grain and biomass yield components was high (33-92%) across environments. There was a significant correlation between stress tolerance index (STI) for grain weight across WS1 and WS2. GWAS revealed that SbZfl1 and SbCN12, orthologs of maize flowering genes, likely underlie flowering time variation under these conditions. GWAS further identified associations (n = 134) for STI and drought effects on yield components, including 16 putative pleiotropic associations. Thirty of the associations colocalized with Stg1–4 loci and had large effects. Seven lead associations, including some within Stg1, overlapped with positive selection outliers.Our findings reveal natural genetic variation for drought tolerance-related traits, and suggest a broad role of Stg loci in drought adaptation of sorghum.

Panicle mold infestation is reported to cause 30–100% yield loss in sorghum. Therefore, breeding for mold resistance becomes a necessity. Due to difficulties in predicting genotype by environment interactions (GxE), multi-location tests are required in the breeding process to identify high-yielding and stable genotypes across environments. The present study aimed at assessing the performance and stability for yield and resistance to grain mold of five local sorghum hybrids evaluated over five years across four locations in the Center and South-East regions of Senegal. The combined ANOVA showed a strong effect of year, genotype and location on the days to anthesis, plant height, grain yield components and panicle grain mold rating score. The GxE interaction was significant for grain yield but not for panicle mold infestation. Year x location explained 25% of total variation of grain yield while year and location explained 22% and 19% respectively. With regard to panicle grain mold infestation, year explained 32% of total variation followed by year by location (29%), genotype (7%) and location (6%). Although year and location better explained the variation for the traits, broad-sense heritability was high, indicating a possibility to improve these traits through selection. For most of the traits, the hybrids had higher performance compared to the parental lines used as check, showing an expression of heterosis. The GGE biplot approach was used to identity hybrids with high performance and stability. Hence, hybrid G4 followed by G2 and G3, were the best in terms of yield performance and stability. Moreover, location STM15 followed by DAR15 were the best closest to an ideal location. Overall, G5 was pointed out as the best hybrid combining grain yield and mold tolerance across years and locations. These results in addition to providing details on the performance and stability of the five sorghum hybrids helped to identify the best hybrids to be released and disseminated in the Center and South-East regions of Senegal.

Summary Unlike most of the important food crops, sesame can survive drought but severe and repeated drought episodes, especially occurring during the reproductive stage, significantly curtail the productivity of this high oil crop. Genome‐wide association study was conducted for traits related to drought tolerance using 400 diverse sesame accessions, including landraces and modern cultivars. Ten stable QTLs explaining more than 40% of the phenotypic variation and located on four linkage groups were significantly associated with drought tolerance related traits. Accessions from the tropical area harboured higher numbers of drought tolerance alleles at the peak loci and were found to be more tolerant than those from the northern area, indicating a long‐term genetic adaptation to drought‐prone environments. We found that sesame has already fixed important alleles conferring survival to drought which may explain its relative high drought tolerance. However, most of the alleles crucial for productivity and yield maintenance under drought conditions are far from been fixed. This study also revealed that pyramiding the favourable alleles observed at the peak loci is of high potential for enhancing drought tolerance in sesame. In addition, our results highlighted two important pleiotropic QTLs harbouring known and unreported drought tolerance genes such as SiABI4, SiTTM3, SiGOLS1, SiNIMIN1 and SiSAM. By integrating candidate gene association study, gene expression and transgenic experiments, we demonstrated that SiSAM confers drought tolerance by modulating polyamine levels and ROS homeostasis, and a missense mutation in the coding region partly contributes to the natural variation of drought tolerance in sesame.

Combining resistance to grain mold with high grain yield in tannin-free white-grained photoperiod-insensitive sorghum is of major interest for farmers in Senegal. In this study, GGE biplot analysis was used to assess the performance, adaptability, and stability of eleven sorghum parental lines and their hybrid combinations for yield and grain mold resistance under Senegalese environments. Eleven inbred lines along with their 22 hybrid combinations and one check were evaluated across three sites during the 2015 and 2016 rainy seasons under natural grain mold infestation. The results of this study showed strong genetic variability among studied genotypes for all measured traits. The highly significant G × E interaction effects for grain yield and panicle grain mold rating score (PGMR) indicated that both traits are influenced by genetics and to some extent by environment. Broad-sense heritability computed was high for all these traits except PGMR, showing a high environmental pressure on this later. The study showed that grain mold pressure in the studied sites decreased following a South-North gradient similar to the rainfall pattern, with the south region wetter, explaining the high disease pressure in Darou and Sinthiou Maleme contrary to Bambey. The GGE biplot analysis performed showed that the first two principal components explained 85.84% of the total variation of GGE sum of squares for grain yield. The which-won-where view of the GGE biplot for grain yield showed that the hybrid HB16 was the most adapted for Bambey area. The ranking of genotypes based on both yield performance and stability showed that HB16, HB5, HB21, HB18, and HB7 were the best hybrids combining high grain yield, high stability performance, and tolerance to grain mold disease across the test environments. These hybrids outperformed the best yielding inbred line P29 (2196.7 kg ha−1) with grain yield advantages ranging 17–60%. Therefore, these hybrids could be recommended to farmers in order to improve sorghum yield in Senegal.

Sorghum is a staple food for over 500 million people in Sub-Saharan Africa and Asia, however, sorghum proteins are poorly digested when wet-cooked. Three sorghum mutants were identified in a mutagenized population of the inbred line BTx623 that showed a 23-37% increase in wet-cooked protein digestibility compared to their unmutagenized parent. Furthermore, in comparison to the known high lysine, highly digestible sorghum mutant, P721Q, these mutants had 9% more protein overall that was 10% more digestible, had 12% more lysine, as well as better seed hardness. Using bulked segregant analysis based on whole genome sequencing data, we identified unique genomic regions on chromosome 5 of each EMS mutant that are associated with the increase in protein digestibility. Analyzing shared mutations in candidate genes, the high protein digestibility phenotype in one mutant is linked to a point mutation in a novel, ankyrin repeat protein. In another, the increase is associated with a mutation in a kafirin gene and suggests novel genetic modifiers. This study provides material and molecular markers that can be used to enhance sorghum nutritional value, contribute to fighting malnutrition and elucidate new roles for ankyrin-repeat proteins in plants.One sentence summaryMutations in a novel, ankyrin domain protein and genetic modifiers of a known mutation in a seed storage protein lead to increased digestibility of seed proteins in sorghum after wet cooking.

Downy mildew of pearl millet induced by Sclerospora graminicola is a major disease that causes significant yield losses in most pearl millet production areas worldwide. The pathogenic variability of S. graminicola populations from four agro-ecological zones in Senegal was assessed under field conditions. A set of 19 pearl millet lines, including 12 downy mildew-resistant differential lines with five improved cultivars and two local checks was evaluated during two consecutive rainy seasons (2015 and 2016) at Bambey, Nioro, Kolda and Sinthiou, representing the main pearl millet-growing zones of Senegal. Significant differences were observed among the tested lines, pathogen origin, year and their interactions for resistance to S. graminicola. Except for ICMR 356 and 7042 S, the downy mildew-resistant differential lines differed in their resistance to the pathogen from the four agro-ecological zones over the years, providing evidence that the S. graminicola isolates represented different races of the pathogen. Among the locations where the experiments were established, the highest average of downy mildew incidence over the two years was recorded at Nioro (18.7 ± 2.6%), Kolda (17.6 ± 1.8%) and Bambey (12.1 ± 2.3%), while the mean downy mildew incidence was lowest at Sinthiou (6.9 ± 2.9%). This finding indicated that populations of pathogen from Kolda, Nioro and Bambey are more virulent compared to the one from Sinthiou.

Sesame is an important oilseed crop in Africa and Asia, owing to its high nutritional quality seed and market value. Variation in sesame seed components including oil, oleic acid, linoleic acid, and protein was investigated by near-infrared reflectance spectrometry in 139 samples collected from different countries. Oil and protein contents were between 40.8% and 60.3% (mean 53.0%) and 15.5% to 25.5% (mean 20.4%), respectively. Linoleic acid, ranging from 31.8% to 52.4% (mean 46%) was more abundant than oleic acid (31.8%–50.6%, mean 38.1%). Light-seeded samples displayed higher nutritional quality, as they were richer in oil, protein, and linoleic acid than dark seeds. Samples from Africa had higher oil and linoleic acid contents, while Asian samples had higher oleic content. The analysis revealed West African sesame cultivars containing especially high levels of seed components, which may command high market values. Two clusters of sesame samples grouped by seed composition were obtained, including one cluster with high oil and oleic acid content and the other with high protein and linoleic acid content. This study revealed that sesame samples from Africa and Asia harbor high variation for major seed components and also provided background information for breeding high-nutrition varieties according to the demands of sesame seed markets.

Multi-parent advanced generation inter-cross (MAGIC) populations are an emerging type of resource for dissecting the genetic structure of traits and improving breeding populations. We developed a MAGIC population for cowpea (Vigna unguiculata L. Walp.) from eight founder parents. These founders were genetically diverse and carried many abiotic and biotic stress resistance, seed quality and agronomic traits relevant to cowpea improvement in the United States and sub-Saharan Africa, where cowpea is vitally important in the human diet and local economies. The eight parents were inter-crossed using structured matings to ensure that the population would have balanced representation from each parent, followed by single-seed descent, resulting in 305 F8 recombinant inbred lines each carrying a mosaic of genome blocks contributed by all founders. This was confirmed by single nucleotide polymorphism genotyping with the Illumina Cowpea Consortium Array. These lines were on average 99.74% homozygous but also diverse in agronomic traits across environments. Quantitative trait loci (QTLs) were identified for several parental traits. Loci with major effects on photoperiod sensitivity and seed size were also verified by biparental genetic mapping. The recombination events were concentrated in telomeric regions. Due to its broad genetic base, this cowpea MAGIC population promises breakthroughs in genetic gain, QTL and gene discovery, enhancement of breeding populations and, for some lines, direct releases as new varieties.

Pearl millet is an important cereal crop for smallholder farmers’ food security in Africa and India. However, its production has stagnated due to several factors such as downy mildew (DM). Thus, a study was conducted to identify new sources of resistance from pearl millet inbred lines derived from a collection of landraces originated from West and Central African countries. A set of 101 lines, including 99 inbred lines from West and Central Africa along with a 7042S and SOSAT C 88 as susceptible and resistant checks, respectively, were evaluated under field conditions with infector rows in Bambey and Nioro research stations during the rainy season of 2016. Data on DM incidence and severity, plant height, flowering time, panicle length and productive tillers were recorded. The results showed highly significant differences among lines for all observed traits. Among the tested lines, 55 including SOSAT C 88 were resistant, 16 moderately resistant and 30 including 7042S were susceptible to the disease. Out of the 55 resistant lines, 20 were disease free. Hierarchical ascendant cluster analysis grouped the lines into three clusters with the DM parameters and plant height as the most discriminant factors. Cluster II contains the susceptible lines, while cluster III comprises the moderately resistant lines. The lines which belongs to cluster I were characterized by their resistance to the disease. Further use of these available new sources of resistance will be very useful for improvement of pearl millet for DM resistance and other agronomic traits.

During the last decade, Jatropha curcas L. (J. curcas) has gained much attention worldwide as biofuel crop. Although its cultivation is promoted in the Sahel, there is a surprising lack of data on its water use regulation and growth in this region. Here, we investigated, in semi-controlled conditions, leaf transpiration and growth of six accessions of J. curcas at seedling stage under natural changing in vapour pressure deficit (VPD) and progressive soil drying in Senegal. The experimental layout was a randomized complete bloc design and after 3 months of growth arranged to a split-plot at the implementation of water stress to facilitate irrigation. Under well water condition, there was no significant difference between accessions for leave transpiration that was positively correlated to VPD with high values recorded between 13 h and 14 h pm. Accessions of J. curcas used in this study showed closed thresholds at which transpiration declined except accession from Ndawene that threshold was lower (0.30). There is no significant difference between accessions for growth during the experimentation period. In 3 months, we recorded 23.57 g for the aboveground dry biomass and seedlings had about 14 leaves and 24.3 cm height. Positive linear correlation was recorded between aboveground biomass and root dry weight (p J. curcas might need complement irrigation for a better growth of seedlings especially during the dry season.

Background West Africa’s Sahel is characterized by a dry and hot climate with limited rainfall that impairs the production of several crops. Sesame is a resilient crop that is well suited to this environment. Unfortunately, there is a lack of data relative to the status of its production in West Africa. We made investigations in four major sesame-growing areas of Senegal and Mali, into the status of the crop’s production, its agronomic practices, the challenges farmers face and their preferences concerning the traits that should be improved. Results A total of 256 sesame producers in 47 villages were interviewed using a semi-structured questionnaire. The results showed that sesame is a multi-ethnic crop and only 20% of the total fields owned by farmers were allocated to its cultivation. The yield and the seasonal production of sesame per farmer was quite weak showing that this crop is still a commodity grown on a small scale. Various cultivars were grown, and the most widely grown ones have considerable levels of oil (53–60.34%) and protein (18–21.89%) contents. In both countries, seed marketing was the main impediment the producers faced on account of a lack of reliable markets and of a considerable fluctuation in prices. Conclusions Overall, the sesame sector is still traditional but is progressively developing and sesame could become an important cash crop for smallholders in West Africa’s Sahel. Research programs should target the release of the varieties with higher yield, a stronger resistance to drought, heat, diseases and pests, a good seed quality and improved plant architecture. This study represents the first insight into the sesame sector in West Africa’s Sahel, and our findings may guide researchers and policy-makers to boost this sector for ensuring food security and the improvement of small-scale farmers’ livelihood.

Key message This paper combined GWAS, meta-analysis and sequence homology comparison with common bean to identify regions associated with seed size variation in domesticated cowpea. Abstract Seed size is an important trait for yield and commercial value in dry-grain cowpea. Seed size varies widely among different cowpea accessions, and the genetic basis of such variation is not yet well understood. To better decipher the genetic basis of seed size, a genome-wide association study (GWAS) and meta-analysis were conducted on a panel of 368 cowpea diverse accessions from 51 countries. Four traits, including seed weight, length, width and density were evaluated across three locations. Using 51,128 single nucleotide polymorphisms covering the cowpea genome, 17 loci were identified for these traits. One locus was common to weight, width and length, suggesting pleiotropy. By integrating synteny-based analysis with common bean, six candidate genes (Vigun05g036000, Vigun05g039600, Vigun05g204200, Vigun08g217000, Vigun11g187000, and Vigun11g191300) which are implicated in multiple functional categories related to seed size such as endosperm development, embryo development, and cell elongation were identified. These results suggest that a combination of GWAS meta-analysis with synteny comparison in a related plant is an efficient approach to identify candidate gene (s) for complex traits in cowpea. The identified loci and candidate genes provide useful information for improving cowpea varieties and for molecular investigation of seed size. Electronic supplementary material The online version of this article (10.1007/s00122-019-03407-z) contains supplementary material, which is available to authorized users.

The combined production of grain and sugar by sorghum requires efficient leaf C acquisition (source) and allocation to productive sinks, namely the stem and the panicle. Photoperiod sensitivity, which regulates plant phenology and growth, is also likely to be a key regulator of such C source-sink relationships, while it is crucial to drought adaptation. This study set out to evaluate the contribution of plant leaf area and stem growth to the production of grain and sugar by sweet, photoperiodic sorghum depending on the sowing date and post-flowering water availability. Twelve West African accessions were studied in the field in Senegal during two consecutive rainy seasons, comparing two sowing dates and post-anthesis water regimes (irrigated, or not). Plant growth and development were monitored weekly up to flowering. Organ size and biomass, stem juiciness and sweetness were characterized at flowering and maturity. At flowering, early sowing enhanced plant leaf area, stem dry weight and sugar production, and plant leaf area expressed per unit of stem dry weight was positively correlated to stem sweetness, suggesting that a high pre-flowering source-to-sink ratio favors early sugar accumulation. Overall, a late sowing date reduced sugar and grain production more than post-anthesis drought, whereas early sowing enhanced both types of production. No post-anthesis competition was found between grain filling and stem sugar accumulation. However, under drought conditions, the maintenance of combined production was better for the most leaf stay-green accessions. It is suggested that the combined production of sugar and grain by sweet, photoperiodic sorghum in response to the sowing date and post-anthesis drought is firstly sink-driven but that source (plant leaf area) dynamics can enhance stem sugar accumulation and its maintenance under drought conditions. These results provide further insight into the traits to be combined in dual-purpose ideotypes dedicated to drought-prone environments.

DNA methylation is a heritable epigenetic mechanism that participates in gene regulation under abiotic stresses in plants. Sesame (Sesamum indicum L.) is typically considered a drought-tolerant crop but highly susceptible to waterlogging, a property attributed to its presumed origin in Africa or India. Understanding DNA methylation patterns in sesame under drought and waterlogging conditions can provide insights into the regulatory mechanisms underlying its contrasting responses to these principal abiotic stresses. Here, we combined Methylation-Sensitive Amplified Polymorphism and transcriptome analyses to profile cytosine methylation patterns, gene expression alteration, and their interplay in drought-tolerant and waterlogging-tolerant sesame genotypes under control, stress and recovery conditions. Our data showed that drought stress strongly induced de novo methylation (DNM) whereas most of the loci were demethylated (DM) during the recovery phase. In contrast, waterlogging decreased the level of methylation under stress but during the recovery phase, both DM and DNM were concomitantly deployed. In both stresses, the differentially expressed genes (DEGs) were highly correlated with the methylation patterns. We observed that DM was associated with the up-regulation of the DEGs while DNM was correlated with the down-regulation of the DEGs. In addition, we sequenced 44 differentially methylated regions of which 90% overlapped with the promoters and coding sequences of the DEGs. Altogether, we demonstrated that sesame has divergent epigenetic programs that respond to drought and waterlogging stresses. Our results also highlighted the possible interplay among DNA methylation and gene expression, which may modulate the contrasting responses to drought and waterlogging in sesame.

Cowpea (Vigna unguiculata L. Walp) is a warm-season legume with a genetically diverse gene-pool composed of wild and cultivated forms. Cowpea domestication involved considerable phenotypic changes from the wild progenitor, including reduction of pod shattering, increased organ size, and changes in flowering time. Little is known about the genetic basis underlying these changes. In this study, 215 recombinant inbred lines derived from a cross between a cultivated and a wild cowpea accession were used to evaluate nine domestication-related traits (pod shattering, peduncle length, flower color, days to flowering, 100-seed weight, pod length, leaf length, leaf width and seed number per pod). A high-density genetic map containing 17,739 single nucleotide polymorphisms was constructed and used to identify 16 quantitative trait loci (QTL) for these nine traits. Based on annotations of the cowpea reference genome, genes within these regions are reported. Four regions with clusters of QTL were identified, including one on chromosome 8 related to increased organ size. This study provides new knowledge of the genomic regions controlling domestication-related traits in cowpea as well as candidate genes underlying those QTL. This information can help to exploit wild relatives in cowpea breeding programs.

Pearl millet is an important cereal crop for smallholder farmers’ food security in West and Central Africa. However, its production has stagnated due to several factors such as the continuous use of local populations. A set of 17 inbred lines was crossed with Sosat C 88 and Souna 3 following a line × tester mating design. The F1 hybrids, their parents, and a check were evaluated in Bambey and Nioro research stations during the rainy season of 2017. Data on downy mildew incidence, plant height, flowering time, panicle length and diameter, productive tillers, thousand-grain weight, panicle, and grain yield were recorded. GCA and SCA mean squares were significant for most of the traits indicating that both additive and nonadditive gene effects were involved in the control of the inheritance of these traits. However, the contribution of GCA to total mean squares was higher than that of SCA for all the traits, providing that additive gene action was more important in their inheritance. The top-cross hybrid IBL155-2-1 × Sosat C 88 exhibited negative and significant SCA effects for downy mildew incidence, flowering time, and plant height. Lines IBL003-B-1, IBL091-1-1, IBL095-4-1, IBL110-B-1, and IBL 206-1-1 had positive GCA effects for grain yield and negative GCA effects for downy mildew, flowering time, and plant height. These lines can be used as parents to create synthetic varieties or hybrids.

Sesame is an important crop in West and Central Africa playing a role of an alternative cash crop for smallholders. However, sesame productivity is highly impaired by drought. This study aimed at identifying some drought-resistant genotypes and efficient screening traits in large sesame germplasm. Ten genotypes were examined based on 21 biochemical, physiological, agromorphological and seed quality traits under three weeks of water stress. A high variability for drought resistance was observed among the genotypes. The genotypes WC17, WC18 and WC14 were drought resistant, WC12, WC13, WC06 and WC03 were moderately drought resistant while, WC02, WC10 and WC08 were drought sensitive, based on principal component analysis. The resistant genotypes exhibited both avoidance and tolerance features including increase of the root system, reduced water loss, highest activity of antioxidative enzymes and accumulation of proline. They produced higher biomass and had higher ability to maintain seed quality under drought stress compared with the sensitive genotypes. Strong accumulation (~200% ratio stress/control) of biochemical markers including superoxide dismutase, ascorbate peroxidase, catalase and proline could be regarded as an important indicator for selecting drought resistant genotypes. This study represents a reference for future research towards developing new varieties with improved drought resistance in West and Central Africa.

Charcoal rot disease causes heavy yield losses to many hosts including cowpea (Vigna unguiculata) and groundnut (Arachis hypogea) in Senegal. The causal agent of the disease was a longtime considered to be Macrophomina phaseolina. However, a new Macrophomina species, Macrophomina pseudophaseolina was reported recently to also cause charcoal rot disease alone or in association with M. phaseolina on several hosts in Senegal. Since 1969, charcoal rot has become increasingly important in cowpea and other crops in the Sahel. It was not known if this status is correlated with the occurrence of the new Macrophomina species. This study therefore aimed to investigate the pathogenicity of M. phaseolina and M. pseudophaseolina on three varieties of cowpea under two temperature regimes. Ten M. pseudophaseolina and nine M. phaseolina isolates were tested on three cowpea varieties in a complete randomized design. Plants were grown in infected soil at two growth temperatures (24/34 and 26/36°C) in a climatic chamber. Disease incidence, level of tissue infection and potential primary inoculum produced in cowpea plants were determined 45 days after planting. By and large, the two Macrophomina species showed the same results, except that at 36°C, M. pseudophaseolina induced more disease development than M. phaseolina in the susceptible cv. Mouride. In conclusion, M. pseudophaseolina induces less disease incidence on cowpea at 34°C than at 36°C. At this temperature, it becomes as damageable as M. phaseolina on cowpea. Key words: Macrophomina phaseolina, Macrophomina pseudophaseolina, growth temperature, disease incidence, potential primary inoculum.

Single nucleotide polymorphism (SNP) markers were used to develop a genetic-linkage map and to identify QTLsinvolved in the genetic variation of agronomical traits in cowpeaunder two water regimes. A total of 1536 SNP GoldenGate assay were used to screen for polymorphism in a cowpea population of recombinant inbred lines. A total of 299 SNP markers amplified polymorphic products of which 228 mapped to the 11 cowpea linkage groups with an average distance of 6.5 cM between markers. The new SNP genetic map with a total length of 1281,8 cM were aligned with the consensus cowpea map allowing filling some gaps, which will increase QTLs analysis. A total of 31 QTLs affecting agronomic traits were identified and mapped to cowpea genomic regions. Among them 45% explaining from 3 to 35% of genetic variation were detected for both water conditions. Co-locations between QTLs were identified on several linkage groups among them QTLs affecting harvest index (HI) and grain yield suggesting their common genetic bases. Because, HI has been shown as the most stable and highly correlated parameter with cowpea yield under stress; our results will enable the efficiency of MAS and enhance genetic progress in cowpea.

Sweet sorghum is highly coveted to contribute and take up food and energy challenges. A collection of 84 West Africa landraces mostly from Senegal and four control cultivars were screened to identify relevant accessions and trait combination for multi-purpose (sugar/grain/biomass). The implication of photoperiod sensitivity was particularly addressed. A total of 20 traits related to phenology, morphology, grain and sugar production were assessed in two sowing dates (July and August) at CNRA Bambey in Senegal. Late sowing resulted in shortened vegetative phase and a significant decrease in traits related to plant size, stem sugar, biomass and grain productions. Broad-sense heritability was moderate to high for most of the phenology, morphology, grain and sugar-related traits, suggesting their interest for breeding. All the traits related to plant size were positively correlated with plant sugar production except plant height. A cluster analysis identified three groups contrasting in their ability to combine sugar, grain or fodder production based on 18 traits measured for the early sowing. Clusters I and III were suitable for one purpose: grain and sugar, respectively. Cluster II was the most suitable for multi-purpose, showing the best trade-off among grain, sugar and vegetative biomass production. The best accessions for stem sugar yield belonged to durra, caudatum and their intermediate types. The relationship between internode size and sweetness should be further studied, in particular exploring their relationship with internode tissue anatomy. Further studies are also needed to evaluate the role that stay-green can play in sugar yield maintenance under post-flowering drought. (Resume d'auteur)

Heterotic grouping based on combining ability for traits of interest, in addition to plant performance and genetic relationship among germplasm, would be useful in planning crosses in breeding programmes. This study aimed at determining the combining abilities of selected landraces for morphological and physiological traits under contrasted environments and identifying the suitable heterotic grouping method for superior hybrid production. For this purpose, nineteen accessions representing different origins and population structure among West African Sorghum Accessions Panel (WASAP) and two female lines, were used in « Line x tester » mating design to produce thirtyeight (38) hybrids. Analysis of variance showed significant general combining ability and specific combining ability effects for grain weight, plant height, days to flowering, panicle length and chlorophyll content implying existence of heterotic responses for these traits. Both additive and non-additive gene effects were important in controlling the inheritance of the traits. Parents K31.3, K37 and Ni331 were the best combiners for grain weight, providing the opportunity for breeders to improve grain yield under diverse environments. AVG-1 x K31.3 and AVG-1 x Tg148 were the superior hybrids. Combining ability based heterotic grouping methods classified sorghum accessions into four groups. The heterotic group’s specific and general combining ability (HSGCA) method was the suitable in predicting hybrid superiority. This combining abilities based heterotic grouping study is an additional tool that breeders could use to identify the best parents for superior hybrids development in West Africa. Key Words : Combining ability, heterotic groups, sorghum, West Africa

Cowpea (Vigna unguiculataL. Walp) is a warm-season legume with a genetically diverse gene-pool composed of wild and cultivated forms. Cowpea domestication involved considerable phenotypic changes from the wild progenitor, including reduction of pod shattering, increased organ size, and changes in flowering time. Little is known about the genetic basis underlying these changes. In this study, 215 recombinant inbred lines derived from a cross between a cultivated and a wild cowpea accession were used to evaluate nine domestication-related traits (pod shattering, peduncle length, flower color, flowering time, 100-seed weight, pod length, leaf length, leaf width and seed number per pod). A high-density genetic map containing 17,739 single nucleotide polymorphisms was constructed and used to identify 16 quantitative trait loci (QTL) for these nine domestication-related traits. Candidate genes underlying each of those 16 QTL were identified. Four regions with clusters of QTL were identified, including one on chromosome 8 related to increased organ size. This study provides new knowledge of the genomic regions controlling domestication-related traits in cowpea as well as candidate genes underlying those QTL. This information can help to exploit wild relatives in cowpea breeding programs.Key messageThis study identified regions of the cowpea genome that played an important role in cowpea domestication, including a hotspot region for increased organ size

Sesame is an important oilseed crop with a high oil quality. It is prone to drought stress in the arid and semi-arid areas where it is widely grown. This study aims to decipher the response of tolerant (DT) and sensitive (DS) genotypes to progressive drought based on transcriptome, biochemical and physio-anatomical characterizations. Results indicated that under severe stress, DT relied on a well-functioning taproot while DS displayed a disintegrated root due to collapsed cortical cells. This was attributed to a higher accumulation of osmoprotectants and strong activity of antioxidant enzymes especially peroxidases in DT. From roots, DT could supply water to the aboveground tissues to ensure photosynthetic activities and improve endurance under stress. Temporal transcriptome sequencing under drought further confirmed that DT strongly activated genes related to antioxidant activity, osmoprotection and hormonal signaling pathways including abscisic acid and Ethylene. Furthermore, DT displayed unique differentially expressed genes in root functioning as peroxidases, interleukin receptor-associated kinase, heat shock proteins, APETALA2/ethylene-responsive element-binding protein and mitogen activated protein kinase, to effectively scavenge reactive oxygen species and preserve root cell integrity. Finally, 61 candidate genes conferring higher drought tolerance in DT were discovered and may constitute useful resources for drought tolerance improvement in sesame.

Development and analysis of Multiparent Advanced Generation Inter-Cross (MAGIC) populations have been conducted with several crop plants to harness the potential for dissecting the genetic structure of traits and improving breeding populations. We developed a first MAGIC population for cowpea (Vigna unguiculataL. Walp.) from eight founder parents which are genetically diverse and carry many abiotic and biotic stress resistance, seed quality and agronomic traits relevant to cowpea improvement in sub-Saharan Africa (SSA) where cowpea is vitally important in the human diet and in local economies. The eight parents were inter-crossed using structured matings to ensure the population would have balanced representation from each of the founder parents, followed by single-seed descent, resulting in 365 F8 recombinant inbred lines (RILs) each carrying a mosaic of genome blocks contributed from all founders. This was confirmed by SNP genotyping with the cowpea Illumina 60K iSelect BeadArray. Following filtering to eliminate duplicates, sister lines and accidental selfing events, a core set of 305 F8 RILs was chosen as the primary population. The F8 lines were on average 99.74% homozygous while also diverse in agronomic traits including flowering time, growth habit, maturity, yield potential and seed characteristics across environments. Trait-associated SNPs were identified for most of the parental traits. Loci with major effects on photoperiod sensitivity and seed size were also verified by genetic mapping in biparental RIL populations. The distribution of recombination frequency varied considerably between chromosomes, with recombination hotspots distributed mostly in the telomeric regions. Due to its broad genetic base, this cowpea MAGIC population promises breakthroughs in genetic gain and high-resolution genetic mapping for gene discovery, enhancement of breeding populations and, for some lines, direct releases as new varieties.

Summary Cowpea (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 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 4,355 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 biparental 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. This article is protected by copyright. All rights reserved.

3 Abstract: The effect of substituting corn with sorghum grains with low tannin content (LTC) on broiler s performances was investigated in a 6-week feeding trial. Seven hundred fifty 1-day old chicks and not sexed Coob 500 were used in this test. These animals were separated into five groups with three replicates of 50 birds for each one. A control diet with 50% of corn was used in the control group. Three other diets where corn was substituted by conventional sorghum in 1/3, 2/3 and 3/3 were given respectively to the G1/3, G2/3 and G3/3 groups. The GLTC groups received diets with total substitution of maize by sorghum with LTC. No significant difference was shown for the body weight between the control and the GLTC groups (respectively 1303 and 1418 g). But the use of conventional sorghum decreases significantly the broilers weight live (p>0.05) with the lower weight performances (1128 to 1225 g). Mortalities were similar for the different groups. It's always results to climatic environment which was identical for the different group. No difference has been observed for the carcass dressing percentage (68 to 76%). For the nutrients digestibility, except the fat matter which was difference and higher (more than 92%), dry matter, ash and then metabolizable energy were similar (p>0.05) in the starting and growing diets.

Available drought-tolerant cowpeas [ Vigna unguiculata (L.) Walp.] are few, and identifica-tion of additional genotypes with even greater tolerance to drought would enable breeders to develop cultivars with higher and more stable yields across the semiarid ecologies where this crop is grown. The objectives of this work were to evaluate the effects of drought on the growth and reproduction of a diverse set of cowpea germplasm and select drought-tolerant and high-yielding genotypes using stress tolerance indices. Thirty short- and 30 medium-duration genotypes were separately assessed in adja-cent drought-stressed (DS) and nonstressed (NS) environments in a randomized complete block design with three replications. Selection indices, including stress tolerance index (STI) and geometric mean productivity (GMP), were estimated considering grain yield under NS and DS environments and the stress intensity. Over-all, the medium-duration genotypes had higher yields than the short-duration ones under both DS and NS conditions. On average, fodder and grain yields were 40 and 65% less under DS con -ditions and maturity occurred 4 d earlier. IT85F-3139, IT93K-693-2, IT97K-499-39, IT93K-503-1, IT96D-610, IT97K-207-15, KVx-61-1, KVx-403, KVx-421-25, and Mouride had the highest grain yields under both DS and NS environments and were identified as the most drought-tolerant and high-yielding genotypes based on their rank in terms of STI and GMP values. Therefore, these cultivars may be valuable parents for breeding programs whose objectives include developing drought-tolerant cowpea cultivars.N. Belko, N. Cisse, and N.N. Diop, Regional Research Center for the Improvement of Crops Adaptation to Drought, CERAAS-ISRA, P.O. Box 3320 Thies-Escale, Thies, Senegal; N. Belko and G. Zombre, Dep. of Biology and Ecology, Univ. of Ouagadougou, 03 P.O. Box 7021 Ouagadougou 03, Burkina Faso; N. Cisse and S. Thiaw, Senegalese Institute of Agricultural Research, CNRA-ISRA, P.O. Box 53, Bambey, Senegal; Satoru Muranaka, Japan International Research Center for Agricultural Sciences (JIRCAS) and International Institute of Tropical Agriculture (IITA), PMB 5320, Ibadan, Nigeria; N.N. Diop and J.D. Ehlers, Dep. of Botany and Plant Sciences, Univ. of California, Riverside, CA 92521-0124. Received 9 Dec. 2012. *Corresponding author (ncisse@refer.sn).

Prom, L. K., Perumal, R., Cisse, N., and Little, C. R. 2014. Evaluation of selected sorghum lines and hybrids for resistance against grain mold and long smut fungi in Senegal, West Africa. Plant Health Progress doi:10.1094/PHP-RS-13-0128 Grain mold in sorghum [Sorghum bicolor (L.) Moench] is a major problem worldwide. Damage caused by this fungal disease complex includes a reduction in yield (loss of seed mass), grain density, and germination. Long smut is another important fungal disease in sorghum and is a threat to food security in West Africa. Studies identifying potential sources of resistance for these two diseases in Senegal are limited. The objective of this research was to assess the vulnerability of selected breeding lines and hybrids from the United States to grain mold and long smut in two locations in 2009 and 2010. Four sorghum lines (Sureno, RTx2911, SC719-11E, and IS18760) and four hybrids (Sorghum Partners NK6638, Asgrow A571, AN600 × RN610, and Pioneer 83G19) exhibited low grain mold severity at both locations. The cultivars 3694 and SC748-5 and one hybrid, Novartis 2030/C, were resistant to long smut infection at both locations. Lines BTx623 and RTx430 were found to be highly susceptible to long smut, and therefore the available commercial sorghum hybrids involving these two parental lines’ genetic backgrounds are likely to be vulnerable to long smut. There are no differential responses between lines and hybrids for both grain mold and long smut disease severity. None of the lines or hybrids showed resistance to both diseases.

Sesame ( Sesamum indicum L.) is one of the most important oilseed crops. It is mainly grown in arid and semi-arid regions with occurrence of unpredictable drought which is one of the major constraints of its production. However, the lack of gene resources associated with drought tolerance hinders sesame genetic improvement towards this osmotic stress. The present research aimed at identifying candidate genes associated with drought tolerance in the whole genome of sesame through homology search of known drought associated genes from three relative species, viz., potato, tomato and the well-described model plant Arabidopsis. Based on 2,495 sequences including 1,150 from Arabidopsis , 1,075 from potato and 270 from tomato, comparative analysis against sesame genome led to the identification of a set of 75 candidate genes (42, 22 and 11 from Arabidopsis , potato and tomato, respectively). Mapping results showed that the candidate genes were distributed on the 16 sesame linkage groups. Wide range of genes with various functions identified in this study confirmed that drought tolerance in sesame is under the control of several genes. Based on their functional classification, 2 groups of candidate genes were identified: (a) genes which protect the plant against drought effect; (b) signal transduction genes and transcription factors. Many transcription factors were retrieved including 6 AP2/ERF genes among which 3 were more expressed in drought tolerant material compared to the sensitive one and might play some important roles in drought tolerance in sesame. Our results provided genomic resources for further functional analysis and genetic engineering towards drought tolerance improvement in sesame. Keywords: Sesamum indicum , candidate genes, drought tolerance, orthologous gene, whole genome

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 crop plants. Here we describe foundational genome resources and their application to analysis of germplasm currently in use in West African breeding programs. Resources developed from the African cultivar IT97K-499-35 include bacterial artificial chromosome (BAC) libraries and a BAC-based physical map, assembled sequences from 4,355 BACs, as well as a whole-genome shotgun (WGS) assembly. These resources and WGS sequences of an additional 36 diverse cowpea accessions supported the development of a genotyping assay for over 50,000 SNPs, which was then applied to five biparental 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 genomes of West African breeding lines and landraces have regions of marked depletion of diversity, some of which coincide with QTL that may be the result of artificial selection or environmental adaptation. The new publicly available 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.