Multi-trait stability selection drives genetic gains in cowpea [Vigna unguiculata (L.) Walp.] under high-temperature stress

Cowpea (Vigna unguiculata (L.) Walp.) is a crucial food and fodder crop in regions characterised by high temperatures. However, its reproductive stages are particularly sensitive to heat stress, leading to reduced pollen viability, pod set, and yield. Therefore, developing and deploying high-temperature-tolerant cultivars is crucial for maintaining productivity under changing climatic conditions. A total of 250 diverse cowpea accessions, along with five checks, were evaluated at Baramati and Jodhpur during the 2022–2023 growing season under both normal and late sowing conditions to simulate high-temperature stress. Growth, yield, and physiological traits, including canopy temperature, were measured. Multi-trait stability indices, including the multi-trait genotype-ideotype distance index (MGIDI), the multi-trait stability index (MTSI), the multi-trait mean performance and stability index (MTMPS), Mean Performance and Stability (MPS) analysis and the factor analysis-based BLUP index (FAI-BLUP), were utilised to identify superior genotypes. Further, genetic parameters were also estimated using mixed linear models. Late sowing exposed genotypes to temperatures exceeding 35 °C during flowering, inducing severe reproductive stress; only 147 of 250 accessions successfully flowered and set seeds. Traits such as seed yield, pods per plant, and seeds per pod showed high heritability (≥ 60%) and considerable genetic variation, while canopy temperature exhibited lower variability. Grain yield was positively correlated with pods per plant (r = 0.40) and grains per pod (r = 0.36), and negatively correlated with canopy temperature (r = − 0.35). Multi-trait indices identified 29 superior genotypes, with six [G044 (IC488270), G078 (EC240920), G080 (IC488085), G112 (EC240868), G114 (EC243927), G142 (IC402161)] consistently selected across all models. Predicted selection gains were high for grain yield (+ 18.7%), pods per plant (+ 11.2%), and grains per pod (+ 8.5%). Several genotypes [G066 (EC240878), G080 (IC488085), G112 (EC240868)] demonstrated both high yield and stability across environments. This study reveals substantial genetic variation for high-temperature tolerance in cowpea, highlighting the value of integrating multi-environment phenotyping with multi-trait stability indices for robust selection. The identified genotypes provide immediate candidates for cultivar release and represent valuable genetic resources for breeding programs aiming to develop heat-resilient cowpea varieties. Screened 250 cowpea accessions; 147 reproduced under > 35 °C field heat stress. Grain yield showed high heritability (71.4%) and a wide range (1.0–52.5 g/plant). Multi-trait indices identified 29 superior heat-resilient genotypes. Six genotypes [G044 (IC488270), G078 (EC240920), G080 (IC488085), G112 (EC240868), G114 (EC243927), G142 (IC402161)] were selected across all models owing to multi-trait superiority (high grain yield, 3-4 °C lower canopy temperature under stress). Predicted selection gains: yield + 18.7%, pods + 11.2%, grains per pod + 8.5%.