Lodging resistance in older and modern soybean cultivars

Abstract Brazilian soybean yield has increased over time, coinciding with improvements in lodging resistance in modern cultivars. This study aimed (i) to evaluate the impact of simulated upright growth on yield components of lodging-susceptible (older) and lodging-resistant (modern) cultivars, and (ii) to characterize the morphological changes and biomechanical evolution of stem resistance using a historical set of cultivars (1966–2018). Field experiment used a split-plot design evaluating the response of older and modern cultivars to canopy staking. Greenhouse experiment assessed morphological and biomechanical attributes of cultivars. Results showed that natural lodging historically reduced the yield potential of older cultivars by 36%. Preventing lodging through staking unmasked a latent potential in older cultivars, resulting in a 57% increase in grain yield, driven by a 45.2% increase in grains per plant and a 20.1% increase in grains per pod. Biomechanically, modern cultivars exhibited a localized mechanical reinforcement in the middle third of the stem, where breaking force increased by 107.2% across eras, accompanied by a descriptive increase in middle-stem diameter (+ 46.9%). Modern genotypes demonstrated structural stability and high yields regardless of physical support. We conclude that modern cultivars are characterized by an optimized plant architecture featuring morphological compacting (reduced height and vegetative biomass) and middle-third stem reinforcement, which is essential since greater middle-stem breaking force is associated with higher pod dry weight in modern high-yield environments.