Effect of biofertilizers and putrescine amine on the physiological features and productivity of date palm (Phoenix dactylifera, L.) grown on reclaimed-salinized soil

KEY MESSAGE : Plant growth promoting rhizobia bacteria and mycorrhizae in the presence of putrescine allows and/or enables date palm to increase its adaptation to reclaimed/salinized areas. Amines and biofertilizers play an important role in a plant’s response to adverse environmental conditions including salt and osmotic stress. This study investigates the integration effect of putrescine amine (Put), biofertilizers, and mycorrhizae (My) on the date palm zaghloul genotype irrigated by saline water and grown in reclaimed saline soil. The data collected indicates that selected plant growth promoting rhizobacteria, in the presence of Put, enables the date palm zaghloul genotype to increase its tolerance and adapt to stress conditions in the reclaimed saline soil. Overall, treatments reduced salt-induced oxidative damage in the date palm, resulting in increased productivity and improved fruit quality. The results observed may be a consequence of the increase in photosynthetic pigments, activities of antioxidant enzymes, organic solutes and/or promoting growth substances such as gibberellic acid (GA₃), auxins (IAA) and cytokinin. Moreover, a decrease in the levels of lipid peroxidation and inhibitor substances such as abscisic acid (ABA) may be related. The most effective interaction treatments were seen at 2.5 mM Put due to an increase in the activities of ascorbate peroxidase (APX), glutathione reductase (GR) and superoxide dismutase (SOD) while a decrease in lipid peroxidation was noticed. The combination of Put with plant growth promoting rhizobacteria (PGPR) at a 5 mM concentration as biofertilizer increased diamine oxidase (DAO) and polyamine oxidase (PAO) activities when compared to the other treatments. The activity of these two enzymes can produce hydrogen peroxide (H₂O₂), which may act in structural defense as a signal molecule and decrease the production of polyamines against salt-induced oxidative damage in date palm. We believe that further investigation is needed to understand the tolerance/adaptation mechanisms in date palm grown under stress condition.