Protection of strawberry plants (Fragaria ananassa Duch.) against anthracnose disease induced by Azospirillum brasilense

Abstract

Background and aims Azospirillum brasilense REC3 is a plant growth-promoting and siderophore-producing bacterium isolated from strawberry. Colletotrichum acutatum M11 is the causal agent of anthracnose, an important disease in strawberry crop. The aim of this study was to characterize at the biochemical and molecular level, the systemic resistance induced by A. brasilense on pathogen-challenged strawberry plants. Methods Phytopathological tests were performed; the content of phenolic compounds was determined spectrophotometrically; callose depositions in leaves by aniline blue staining; salicylic acid (SA) content in leaves by HPLC; and defense-related gene expression [pathogenesis-related proteins (FaPR1), chitinases (FaChi2-1; FaChi2-2) and glucanase (FaBG2-2)] by RT-PCR. Results A. brasilense REC3 reduced anthracnose symptoms on pathogen-challenged plants, and the effect became greater as the elapsed time between bacterial inoculation and fungal infection increased. Biochemical and transcriptional studies revealed a transient accumulation of SA and the induction of defense-related genes, suggesting further that this response is related to structural cell wall modifications as consequence of the observed increase in phenolic compounds and callose deposition. Conclusions The plant growth-promoting bacterium A. brasilense REC3 participates actively in the induction of systemic protection on strawberry plants against anthracnose disease caused by C. acutatum M11.