Is there potential to adapt soybean ( G lycine max M err.) to future [ CO 2 ]? An analysis of the yield response of 18 genotypes in free‐air CO 2 enrichment

Rising atmospheric [ CO 2 ] is a uniform, global change that increases C 3 photosynthesis and could offset some of the negative effects of global climate change on crop yields. Genetic variation in yield responsiveness to rising [ CO 2 ] would provide an opportunity to breed more responsive crop genotypes. A multi‐year study of 18 soybean ( G lycine max   M err.) genotypes was carried out to identify variation in responsiveness to season‐long elevated [ CO 2 ] (550 ppm) under fully open‐air replicated field conditions. On average across 18 genotypes, elevated [ CO 2 ] stimulated total above‐ground biomass by 22%, but seed yield by only 9%, in part because most genotypes showed a reduction in partitioning of energy to seeds. Over four years of study, there was consistency from year to year in the genotypes that were most and least responsive to elevated [ CO 2 ], suggesting heritability of CO 2 response. Further analysis of six genotypes did not reveal a photosynthetic basis for the variation in yield response. Although partitioning to seed was decreased, cultivars with the highest partitioning coefficient in current [ CO 2 ] also had the highest partitioning coefficient in elevated [ CO 2 ]. The results show the existence of genetic variation in soybean response to elevated [ CO 2 ], which is needed to breed soybean to the future atmospheric environment.