The effect of in vitro inoculation of strawberry microplants with rhizobacteria strains on their stress response during ex vitro cultivation under hydroponic conditions

Background. Preliminary inoculation of microplants in vitro with growth-promoting rhizobacteria can positively affect their adaptation to ex vitro conditions. The aim of the work was to study the effect of inoculation of strawberry microclones in in vitro culture with Azospirillum baldaniorum Sp245 and Kocuria rosea T1Ks19 on the stress response during ex vitro cultivation under hydroponic conditions.

Materials and methods. Strawberry microplants of cvs. ‘Asia’ and ‘Vima Kimberly’ were used as macrosymbionts. The rhizobacteria from the collection of rhizosphere microorganisms of the Institute of Biochemistry and Physiology of Plants and Microorganisms (Saratov) served as microsymbionts. Co-inoculation with bacteria was carried out in vitro (10⁶ CFU/mL), then 45-day-old plants were planted in a hydroponic setup (ex vitro). The morphometric and biochemical parameters of plants and the number of bacteria on the root surface were analyzed dynamically.

Results. In vitro inoculation of strawberry microplants with rhizobacteria strains did not lead to contamination of the nutrient medium. Both strains were detected on the roots throughout the adaptation period. Bacterization of microplants resulted in a decrease in the root length in both cultivars and the number of leaves in ‘Vima Kimberly’ after 20 days of adaptation, but without changing the shoot biomass. During the adaptation process, the bacterized plants, unlike the controls, maintained a stable level of photosynthetic pigments better. By the 20th day, the amount of pigments in bacterized plants was significantly higher than in the control variants. A cultivar-specific reaction of the activity of antioxidant enzymes (peroxidase, catalase, and ascorbate peroxidase) and malondialdehyde was noted.

Conclusion. It was found that in vitro inoculation of strawberry microplants with rhizobacteria resulted in a decrease in the stress response in plants of cvs. ‘Asia’ and ‘Vima Kimberly’ at the ex vitro cultivation stage.

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