Enhanced fruit yield and quality of tomato by photosynthetic bacteria and CO2 enrichment under reduced irrigation

Reduced irrigation generally induces the tomato fruit yield reduction but enhance the fruit quality. Elevated CO2 (eCO2) injection is a common technique for alleviating water stress while eCO2 could inevitably lead to the element concentration dilution in the plant organs. Inoculated with photosynthetic bacteria (PSB) are confirmed to form a symbiotic relationship with crop roots, thereby promoting root development, and improving crop root nutrient and water uptake capacity. Yet, it remains unknown whether PSB could mitigate the adversely effect of nutrient dilution under eCO2 condition and the yield decline under reduced irrigation. To investigate that, two water treatments, including reduced irrigation (RI, plants were irrigated to 75% field water capacity) and full irrigation (FI, plants were irrigated to 90% field water capacity) of tomato plants, were grown under normal ambient CO2 (aCO2, 400 ppm) and elevated CO2 (eCO2, 800 ppm) conditions, respectively. And photosynthetic bacteria were inoculated in half plants. The results showed that inoculation of PSB improved the effectiveness of CO2 stimulation on biomass and yield in tomato plants grown under reduced irrigation conditions. The stimulation effects have been associated with increased advantages linked to their root system, we have observed that CO2 and PSB inoculation promoted the root development and antioxidant abilities. These consequently increased nitrogen uptake efficiency under eCO2 and reduced irrigation conditions, and increased nitrogen accumulation in various organs. Furthermore, eCO2 and inoculation with PSB individually or in combination ameliorated yield penalties under reduced irrigation conditions. Combined elevated CO2 and inoculation with PSB resulted in the highest fruit quality. Collectively, the responses of tomato fruit yield and quality to water-reduced irrigation regimes are further enhanced by the combination of eCO2 and PSB inoculation, and this would be efficacious in greenhouse tomato cultivation and future agriculture production.