Arbuscular mycorrhizal fungi alleviate oxidative stress in pomegranate plants growing under different irrigation conditions

Drought greatly affects the growth and development of plants. This stressful condition can trigger an increase in reactive oxygen species (ROS) production that, in turn, can induce cellular, anatomical, and morphological changes that improve drought tolerance. A strain of arbuscular mycorrhizal fungi (AMF) is considered efficient when it colonizes roots quickly and extensively, absorbs and transfers nutrients to the plant host, promotes soil aggregation, and protects the host against disease. We evaluated the effect of inoculation of two strains of the AMF Rhizophagus intraradices (N.C. Schenck & G. S. Smith) C. Walker & A. Schussler (GA5 and GC2) on pomegranate plants (Punica granatum L.) under two irrigation conditions. The response to oxidative stress depended on many factors, including the organism tissue and the degree of stress. Our study showed that, in most cases, mycorrhizal plants increased antioxidant defenses, such as the ROS-scavenging enzymes superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) in shoots under both irrigation levels, whereas the response for roots was ambiguous. AMF inoculation maintained the levels of malondialdehyde (MDA), probably by rapidly increasing antioxidant defenses and preventing lipid damage. We show that early AMF inoculation (particularly with the GC2 strain) in pomegranate propagation protects plants against abiotic stress.