Isolation of beneficial bacteria from strawberry (Fragaria x ananassa, Duch): Potentialities for fungal disease control and plant growth promotion

Abstract

The main goal of this work was to isolate and characterize strawberry bacteria with the potential to protect plants from the attack by fungal pathogens, as well as promote plant growth. One hundred and three bacterial isolates (57 epiphytes and 46 endophytes) were obtained from leaves and harvest-ripe fruits of strawberries (cv. San Andreas). An exhaustive characterization of these isolations was carried out both from a biochemical and molecular approach. Forty-seven isolates showed significant inhibition of the in vitro growth of Botrytis cinerea both by the action of diffusible compounds and competition for nutrients or space and by the synthesis of volatile organic compounds. The potential of the isolates as biocontrol agents were evaluated through the ability to produce cellulases, proteases, and lipases, and their capacity to form biofilms. As a result, eight epiphytes and four endophytes which could synthesize at least one of the enzymes and form biofilms were selected to continue studying. The twelve isolates showed swimming and/or swarming type motility. The selected bacteria produced auxins, gibberellins and abscisic acid, as well as phytohormones linked to defence responses such as jasmonic and salicylic acid. Notably, the isolates named HI5, HII1, HIII11, FII13, and FII18 also stood out in their ability to significantly increase the fresh weight of the roots and rosettes of inoculated Arabidopsis thaliana (seedlings or adult plants) compared to the controls. The results obtained are promising to consider the said isolates as biological controllers and growth promoters in a crop of commercial interest as the strawberry.