Effects of short-term exposure to elevated atmospheric CO₂ on yield, nutritional profile, genetic regulatory pathways, and rhizosphere microbial community of common bean (Phaseolus vulgaris)

Aim: Legumes are vital to agroecosystems and human nutrition, yet climate change is compromising their nutritional value. This study aims to assess how a one-month exposure to elevated CO2 (eCO2) impacts biomass yield, mineral profile, gene expression, and the soil microbiome of common bean plants (Phaseolus vulgaris L.). Methods: Phaseolus vulgaris L. was grown in field conditions under ambient CO2 (control, aCO2, 400 ppm) or eCO2 (600 pm) from the start of pod filling until plant maturity and analyzed for several morphophysiological and nutritional parameters. Results: Compared with aCO2, eCO2 exposure significantly increased plant and grain biomass, with fluctuations in mineral accumulation. Notably, it decreased grain iron and zinc concentrations, two essential microelements related to food security, by 59% and 49%, respectively. Additionally, grain phenolic content decreased by up to 41%. Genes involved in mineral uptake (such as FER1, ZIP1, and ZIP16), plant response to stress (TCR1, TCR2, and HLH54) and symbiosis with soil microorganisms (NRMAP7 and RAM2) seemed to regulate effects. Microbiome analysis supported these findings, with an increase in the relative abundance of Pseudomonadota by 10%, suggesting eCO2-induced alterations in microbial community structure. Conclusions: This research demonstrates how eCO2 impacts the nutritional quality of common beans regarding micronutrients and phenolic content, while also affecting soil microbiome composition. Highlighting the value of shorter term eCO2 treatments, the findings provide early insights into immediate plant responses. This underscores the need for crop improvement strategies to address nutrient deficiencies that may arise under future eCO2 conditions.