BGIV

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. Schüßler (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.

The aim of this work was to determinate the effects of two geographically different strains of Rhizophagus intraradices (M3 and GA5) on the total biomass and essential oil (EO) yield and composition of Calamintha nepeta, with or without phosphorus (P) fertilization, under greenhouse conditions. The plant biomass was not significantly affected by any treatments, showing higher values in control plants. Strains had a differential response in their root colonization rates: M3 reduced these parameters while GA5 did not modify them. Both strains affected EO yield in absence of P fertilization: M3 promoted EO yield in C. nepeta plants, and GA5 resulted in negative effects. The percentage composition of EO was not significantly modified by either strain or P fertilization. M3 strain could be a potential fungal bioinoculant for production and commercialization of C. nepeta in the aromatic plants market.

The water regime affects a wide variety of physiological and biochemical processes in plants including an increased production of reactive oxygen species (ROS) capable of causing oxidative damage to proteins, DNA and lipids. Arbuscular mycorrhizal fungi (AMF) colonize a wide range of plant species though the ability of different AMF species to promote host growth or contribute to plant water deficit resistance varies. The first phase of olive tree cultivation takes place in a nursery where plants usually suffer stress by drying. Currently, olive production systems do not use of AMF to counteract this problem. To study the colonization strategies of two AMF strains and their efficiency with respect to growth and their effect on enzymatic activities, we inoculated them individually and co-inoculated then on olive plants under nursery growing conditions. The results showed the benefits generated by these fungi in terms of growth and survival rate. Co-inoculation, particularly, improved growth and reduced the damage due to water stress, partly as a result of the activation of the antioxidant defenses in the olive plant host.