Bacillus amyloliquefaciens Enhanced Strawberry Plants Defense Responses, upon Challenge with Botrytis cinerea

Abstract

Plants activate a range of active defense strategies in response to biotic stresses. Systemic acquired resistance (SAR) occurs when the plants are triggered by a stimulus prior to infection by a plant pathogen able to reduce the severity of the disease. The most widely studied group of PGPB is plant growth-promoting rhizobacteria that colonize the root surface. This trait plays a crucial role in protecting plants from pathogen attack since poor colonization could cause decreased antagonistic activity. The present work aims to isolate, identify and select strains from the rhizosphere of strawberry in the Larache area, with potential application as a biocontrol agent against gray mold disease caused by Botrytis cinerea. First, the selected bacteria and the pathogen were characterized using 16S rDNA and ITS sequencing respectively, and then challenged in dual culture as antagonists to evaluate their effect on the growth of B. cinerea. Among the selected bacteria that inhibited the growth of B. cinerea in vitro dual culture, Bacillus amyloliquefaciens was able to associate to the external root surfaces, by forming biofilm, moreover, preliminary analyses showed that, upon attack with Botrytis cinerea, B. amyloliquefaciens primed strawberry’s plants, showed an enhanced expression of PR1 and β-1,3-glucanase (FaBG2-2) genes in comparison to non-primed plants. However, no expression of chitinase II genes (FaChi2-1, FaChi2-2) was observed. This “priming” effect indicated that B. amyloliquefaciens could be further studied for its biocontrol traits able to induce, once inoculated, defense-related gene expression earlier and stronger than in non-primed plants.