Potential maternal effects of elevated atmospheric CO₂ on development and disease severity in a mediterranean legume

Global change can greatly affect plant populations both directly by influencing growing conditions and indirectly by maternal effects on development of offspring. More information is needed on transgenerational effects of global change on plants and their interactions with pathogens. The current study assessed potential maternal effects of atmospheric CO₂ enrichment on performance and disease susceptibility of first-generation offspring of the Mediterranean legume Onobrychis crista-galli. Mother plants were grown at three CO₂ concentrations, and the study focused on their offspring that were raised under common ambient climate and CO₂. In addition, progeny were exposed to natural infection by the fungal pathogen powdery mildew. In one out of 3 years, offspring of high-CO₂ treatments (440 and 600 ppm) had lower shoot biomass and reproductive output than offspring of low-CO₂ treatment (280 ppm). Disease severity in a heavy-infection year was higher in high-CO₂ than in low-CO₂ offspring. However, some of the findings on maternal effects changed when the population was divided into two functionally diverging plant types distinguishable by flower color (pink, Type P; white, Type W). Disease severity in a heavy-infection year was higher in high-CO₂ than in low-CO₂ progeny in the more disease-resistant (Type P), but not in the more susceptible plant type (Type W). In a low-infection year, maternal CO₂ treatments did not differ in disease severity. Mother plants of Type P exposed to low CO₂ produced larger seeds than all other combinations of CO₂ and plant type, which might contribute to higher offspring performance. This study showed that elevated CO₂ potentially exerts environmental maternal effects on performance of progeny and, notably, also on their susceptibility to natural infection by a pathogen. Maternal effects of global change might differently affect functionally divergent plant types, which could impact population fitness and alter plant communities.