Abstract
Several studies have shown the benefits of plant growth-promoting rhizobacteria (PGPR) on plant mineral nutrition suggesting their application as biofertilizers. PGPR can stimulate plant growth, increase plant resistance to abiotic and biotic stresses and might thus have a positive effect also on fruit quality.
The aim of this work was therefore to evaluate and compare the effects of beneficial microorganisms, supplied either as pure culture (Azospirillum brasilense) or as a commercial mixture (Effective Microorganisms – EMTM), on the growth and quality of strawberry (Fragaria ananassa cv. Elsanta) fruits. Strawberries are in fact among the most popular fruits, because of their unique taste and health benefits for humans, due to a high content of micronutrients, phytochemicals and antioxidants.
Strawberry frigo-plants were hydroponically grown either in a complete nutrient solution, or in a nutrient solution inoculated with A. brasilense or with EM for 10 weeks (Pii et al., 2016). At harvest, biometric parameters, as shoot fresh weght, root fresh weight, and yield parameters, like number of fruits per plant and fruit weight, were recorded.
Growth parameter (e.g. biomass, leaf area) were not affected by the rhizoacteria. Even though PGPR-inoculated plants showed slightly reduced fruit yields in terms of average number of fruits/plant they delivered larger fruits as compared to controls. Fruits obtained from PGPR-inoculated plants had also a higher sweetness index in comparison to control fruits. The content of total phenols showed no significant difference between the different samples, whereas the concentration of flavonoids and flavonols was higher in fruits harvested from A. brasilense-inoculated plants. In addition, PGPRs also influenced the uptake and allocation of nutrients in fruits, in particular increasing the concentration of micronutrients (e.g. Fe).
In conclusion, our results demonstrate that the application of PGPR as biofertilizers might represent a sustainable agricultural practice to improve the nutraceutical value of strawberries, particularly concerning the content of flavonoids and micronutrients.