Cowpea (Vigna unguiculata) is a critical warm-season legume in Sub-Saharan Africa, supplying dietary protein, cash income and livestock feed. Its tolerance to drought and low-fertility soils, together with biological nitrogen fixation, make it suitable for the hot, water-limited agroecologies of Niger. Production is, however, constrained by terminal droughts, low soil fertility, Striga, insect pests and the wide cultivation of unimproved local varieties. In short, improved extra-early cowpea genotypes that deliver both grain and fodder could strengthen food and feed security in Niger’s fragile production zones.
The study objective was to identify extra-early maturing cowpea lines that combine high grain and fodder yields with stability across multiple environments, using multi-environment trials and a suite of stability and multi-trait selection indices.
Twenty-one extra-early cowpea genotypes were evaluated: 19 newly developed breeding lines and two check varieties (UAM09_1055_6 and IT99K573_1_1). The breeding lines were produced at the Institut National de la Recherche Agronomique du Niger (INRAN) using bulk selection. Fifteen lines derived from N’Diambour × IT84S-2246–6, three from G118 × IT87D-1083, and one from G150 × IT87D-1083. Parental lines N’Diambour, G118 and G150 are known for high grain and fodder yield under low phosphorus, while IT84S-2246–6 and IT87D-1083 are early maturing but lower yielding.
Field trials were conducted during the 2021 and 2022 rainy seasons at three southern Niger locations representing principal cowpea production agro-climatic zones: Konni (13°82′ N, 5°28′ E), Maradi (15°26′ N, 8°33′ E) and Magaria (12°59′ N, 6°56′ E). Soils were predominantly sandy across sites; Maradi soil had 72% sand, 11% silt and 17% clay, Magaria 88% sand, 4% silt and 8% clay, while Konni ranged around 70% sand with variable silt and clay. Soil organic carbon was low (Maradi 0.30%, Magaria 0.27%, Konni 0.15%) and pH ranged from 5.4 to 5.8.
Annual rainfall differed by site and year. In 2021 total rainfall recorded were 323.5 mm (Konni), 446.3 mm (Magaria) and 535.6 mm (Maradi). In 2022 rainfall increased to 468.9 mm (Konni), 741.39 mm (Magaria) and 755.2 mm (Maradi).
Trials used a 3 × 7 alpha-lattice design with three replications. Each genotype occupied a four-row plot (4 m long) with 0.5 m spacing between rows and between plants. Two to three seeds per hill were sown and thinned to one plant per stand three weeks after emergence. Manual weeding was performed as needed and insecticide was applied at flowering, pod formation and pod filling stages. Measured traits included phenology, pod and grain yields and fodder yield. Detailed data and supporting information are reported in the paper.
The study analyzed genotype, environment and genotype × environment interaction effects on all traits. Stability of grain and fodder yields was assessed using multiple approaches: Shukla’s stability variance, the cultivar superiority index, Wricke’s ecovalence, GGE biplot analysis and the multi-trait genotype–ideotype distance index (MGIDI). Broad-sense heritability and genetic advance metrics were estimated to evaluate selection potential. The environment component was emphasized in variance partitioning.
Analysis of variance showed significant differences among genotypes, among environments and for genotype × environment interactions for all evaluated traits. Environmental effects produced the largest mean squares for every trait (p < 0.001), indicating that site and year differences strongly influenced performance.
Broad-sense heritability estimates were substantial across traits, ranging from 0.77 for fodder yield to 0.88 for days to 50% flowering. Genetic advance as a percentage of the mean (GAM) was high for yield traits: pod yield 78.67%, grain yield 81.80% and fodder yield 99.59%, indicating strong potential for genetic improvement through selection.
The overall mean grain yield across all genotypes and environments was 1,394.32 kg ha⁻¹. Coefficients of variation ranged from 26.59% for grain yield to 40.63% for fodder yield, reflecting greater relative variability in fodder production across environments.
Using the suite of stability statistics and multi-trait selection via MGIDI, the authors identified ten extra-early lines that combined early maturity with relatively high and stable grain and fodder yields. These lines were: BM22, BP02, BP15, MM142, 65B5080, BP18, BM21, BM13, MM141 and BM12. The study recommends these genotypes for further testing across broader agroecological zones and for assessment against farmer preferences before release or use as parents in breeding.
The results highlight that environmental variation is a dominant driver of cowpea performance across the tested sites and years, underscoring the need for multi-environment evaluation when selecting for stability. High heritability and large genetic advance for yield traits suggest selection within this extra-early germplasm can be effective, particularly when integrated with multi-trait indices such as MGIDI to reconcile yield, maturity and fodder objectives. The identified lines show promise as dual-purpose, climate-resilient options for Sahelian systems characterized by terminal drought and late-season pest pressure.
Twenty-one extra-early genotypes were screened across six environments, and analyses revealed significant genotype, environment and G×E effects, high heritability and strong selection potential for yield traits. Ten lines combined early maturity with high, stable grain and fodder yields and merit expanded testing across diverse agroecological zones and farmer participatory evaluations prior to varietal release or use as parents in breeding programs aimed at improving dual-purpose cowpea for the Sahel. All data and supporting files are available within the paper and its supporting information.