Evaluating common bean elite lines in two contrasting ecologies of north India: eco-phenological dynamics and environment relations to crop yields.

Common bean is traditionally cultivated in the hilly regions of India, but recent breeding efforts aim to introduce this crop into non-traditional plain areas. In this study, twenty-nine exotic common bean lines, along with three local checks, were evaluated using an augmented design in Shimla (Northern Hill Zone, NHZ) during rainy season (July-November) and in Kanpur (Northern Plain Zone, NPZ) during winter (November-March) across two consecutive years (2020-2022). The study objective was to evaluate site-specific genotypic responses to environmental factors, eco-phenological dynamics, genotype-by-environment interactions, and identify superior exotic breeding lines of common bean. Results indicated that crop yield in NPZ was 33-41% lower compared to NHZ. The vegetative and reproductive phases were extended by 7.8-8.7 days and 5.3-6.7 days, respectively, in NPZ compared to NHZ. Notably, minimum temperatures during flowering (TMIN_F) and the reproductive period (TMIN_R), along with relative humidity, showed significant positive associations with yield, highlighting the crop's sensitivity to low temperatures in NPZ. Multivariate analysis revealed that extended crop duration and lower TMIN_F and TMIN_R negatively affected yield. Linear mixed-model analysis confirmed that variation in crop-stage-specific temperatures and the lengths of vegetative and reproductive phases, driven by environmental factors, significantly influenced crop yield. The accessions EC931971, EC931452, and ARUN, which exhibited longer reproductive phases, higher seed weight, and more pods plant^- 1, were identified as high-yielding and stable lines. The study suggests that breeding for low-temperature tolerance is crucial for improving yields in NPZ, and the identified exotic lines could be valuable genetic resources for crop improvement programs.