Soybean phenotypic plasticity in response to dark chilling stress

The expansion of soybean cultivation to high-latitude regions is hindered by the adverse effects of dark chilling stress. This study investigates the phenotypic plasticity of soybean in response to dark chilling stress, aiming to identify traits that contribute to adaptation in northern climates. Five soybean cultivars from early maturity groups (000 and 00) were grown in growth chambers set either at 25/18{degrees}C or 25/10{degrees}C (day/night), and a range of performance and functional traits were measured. The relative distance plasticity index highlighted variations in plasticity across traits and genotypes. Photosynthetic activity recovery traits, shoot growth rate, and tap root elongation rate showed high plasticity and significant differences between cultivars, making them suitable for assessing dark chilling tolerance. Moreover, distinct responses to dark chilling stress were exhibited by different soybean cultivars. For instance, cv. SOPRANA displayed a greater phenotypic plasticity in aboveground performance traits, such as shoot growth, while cv. SULTANA exhibited a greater plasticity in physiological traits like photosynthetic activity recovery. These differing strategies may lead to similar biomass production through distinct mechanisms, highlighting the complexity of soybeans adaptive responses to dark chilling stress. These findings provide valuable insights for breeders seeking to develop soybean cultivars adapted to high latitudes, meeting the increasing demand for locally produced protein-based food. However, further research in real field conditions is essential to validate the potential benefits of these plastic traits and their role in improving soybean resilience to dark chilling stress. The identified plastic traits offer a promising avenue for screening a broader range of cultivars and enhancing soybeans suitability for cultivation in northern regions.