Growth and Nutritional Responses of Bean and Soybean Genotypes to Elevated CO₂ in a Controlled Environment

In the current situation of a constant increase in the atmospheric CO<inf>2</inf> concentration, there is a potential risk of decreased nutritional value and food crop quality. Therefore, selecting strong-responsive varieties to elevated CO<inf>2</inf> (eCO<inf>2</inf>) conditions in terms of yield and nutritional quality is an important decision for improving crop productivity under future CO<inf>2</inf> conditions. Using bean and soybean varieties of contrasting responses to eCO2 and different origins, we assessed the effects of eCO<inf>2</inf> (800 ppm) in a controlled environment on the yield performance and the concentration of protein, fat, and mineral elements in seeds. The range of seed yield responses to eCO<inf>2</inf> was &minus;11.0 to 32.7% (average change of 5%) in beans and &minus;23.8 to 39.6% (average change of 7.1%) in soybeans. There was a significant correlation between seed yield enhancement and aboveground biomass, seed number, and pod number per plant. At maturity, eCO<inf>2</inf> increased seed protein concentration in beans, while it did not affect soybean. Lipid concentration was not affected by eCO2 in either legume species. Compared with ambient CO<inf>2</inf> (aCO<inf>2</inf>), the concentrations of manganese (Mn), iron (Fe), and potassium (K) decreased significantly, magnesium (Mg) increased, while zinc (Zn), phosphorus (P), and calcium (Ca) were not changed under eCO<inf>2</inf> in bean seeds. However, in soybean, Mn and K concentrations decreased significantly, Ca increased, and Zn, Fe, P, and Mg concentrations were not significantly affected by eCO<inf>2</inf> conditions. Our results suggest that intraspecific variation in seed yield improvement and reduced sensitivity to mineral losses might be suitable parameters for breeders to begin selecting lines that maximize yield and nutrition under eCO<inf>2</inf>.