Responsiveness of Durum Wheat to Mycorrhizal Inoculation Under Different Environmental Scenarios

A greater understanding of how climate change will affect crop photosynthetic performance has been described as a target goal to improve yield potential. Other concomitant stressors can reduce the positive effect of elevated atmospheric CO2 on wheat yield. Arbuscular mycorrhizal fungi (AMF) are symbiotic fungi predicted to be important in defining plant responses to rising atmospheric CO2, but their role in response to global climatic change is still poorly understood. This study aimed to assess if increased atmospheric CO2 interacting with drought can modify the effects of mycorrhizal symbiosis on flag leaf physiology in winter wheat. The study was performed in climate-controlled greenhouses with ambient (400 ppm, ACO(2)) or elevated (700 ppm, ECO2) CO2 concentrations in the air. Within each greenhouse half of the plants were inoculated with Rhizophagus intraradices. When ear emergence began, half of the plants from each mycorrhizal and CO2 treatment were subjected to terminal drought. At ACO(2) AMF improved the photochemistry efficiency of PSII compared with non-mycorrhizal plants, irrespective of irrigation regime. Mycorrhizal wheat accumulated more fructan than non-mycorrhizal plants under optimal irrigation. The level of proline in the flag leaf increased only in mycorrhizal wheat after applying drought. Mycorrhizal association avoided photosynthetic acclimation under ECO2. However, nitrogen availability to flag leaves in mycorrhizal plants was lower under ECO2 than at ACO(2). Results suggest that the mechanisms underlying the interactions between mycorrhizal association and atmospheric CO2 concentration can be crucial for the benefits that this symbiosis can provide to wheat plants undergoing water deficit.