S19 - Session O3 - The efficacy of priming agents on agronomic characteristics of raspberry (Rubus idaeus L.) under mild water stress conditions

Authors: George Manganaris *, Vassilis Fotopoulos, Nicolas Valanides, Chrystalla Antoniou

Agricultural biostimulants (ABs), also mentioned as priming agents (PAs), are generally recognized as safe since they do not leave any harmful residues on fruits and are abundant in natural environments. Furthermore, they have been shown to trigger crop protection mechanisms, against abiotic stress factors. The aim of the current study was to test the efficacy of three commercially products [an osmo-conditioning product (OSMO) and two bio-priming agents consisted of Bacillus, Pseudomonas and Streptomyces (BIO1) and a Bacillus amyloliquefaciencs strain (BIO2)] that are being promoted as ABs in raspberry plants (cv. 'Erika'), a value-added soft fruit crop, under control and water deficit conditions. An array of physiological parameters (leaf gas exchange and photosynthetic pigments) and biochemical stress indicators [hydrogen peroxide (H 2 O 2 ), malonaldehyde (MDA) and proline content] in the newly fully developed leaves were assessed. OSMO demonstrated the most promising results by improving plant water status and leaf gas exchange. OSMO-treated plants were characterized by enhanced proliferation of stomatal conductance, higher photosynthetic pigments and proline contents and significantly higher height and number of lateral shoots, leaves and flowers, indicating advanced photosynthetic activity and better adaptation under water deficit conditions. No apparent beneficial effect to justify its use was registered for the rest commercial compounds tested.