e. selective inhibition or inhibition of one but stimulation of another fungus, is commonly observed in bacterium-fungus co-culture bioassays. Garbaye and Duponnois [14], for instance, observed that bacteria which stimulate growth and mycorrhiza formation by L.

bicolor may be inhibitory to Hebeloma cylindrosporum.To date, the study on metabolites related to fungus specificity of mycorrhiza associated bacteria has focused on one Streptomyces isolate. Riedlinger et al. [16] observed that Streptomyces sp. AcH 505 stimulated the growth of the mutualist Amanita muscaria, while inhibiting the plant parasite Heterobasidion annosum[17]. EM formation with A. muscaria was stimulated by Streptomyces sp. AcH 505, and at the same time Norway spruce roots were protected from H. annosum root rot by the

same strain Sorafenib price [15]. The sole inhibition of H. annosum was related to its low level of tolerance to an exudate produced by AcH 505, an antifungal substance WS-5995 B. This indicates that production of antibiotics by mycorrhiza associated bacteria is of central importance in Peptide 17 purchase relation to fungus specificity, controlled stimulation of mycorrhizal infection, and plant protection. There is XAV-939 molecular weight evidence that inoculation of roots with non-pathogenic bacteria may render plants disease resistant. This phenomenon was studied in detail in the interaction between Arabidopsis thaliana and fluorescent pseudomonads and has been termed “priming” [18]. Streptomycetes have also been implicated in the induction of a priming-like state in plants. The inoculation of Arabidopsis seedlings with Streptomyces sp. EN27 led to suppression of Fusarium oxysporum wilt disease in roots and Erwinia carotovora soft rot in leaves [19]. Upon pathogen from challenge, the endophyte-treated plants demonstrated higher levels of defence gene expression compared with the non-Streptomyces-treated controls, indicating a priming-like state in the plant. Streptomyces sp. GB 4-2 acted in a similar

manner against Heterobasidion root and butt rot in Norway spruce seedlings [20]. While the sole inoculation with the plant pathogen led to the lysis of the roots, an anatomical barrier against the root pathogen was formed in the presence of Streptomyces GB 4-2. The needles of Norway spruce were also protected from Botrytis cinerea gray mold infection, indicating a systemic response. Here, we report an assessment study of fungal, bacterial, and plant responses to mycorrhiza-associated streptomycetes. Based on our earlier work with mycorrhizosphere streptomycetes [15, 20–22], we formulated the following hypotheses: (i) streptomycetes impact fungi and bacteria in a streptomycete strain specific manner, (ii) few strains promote the growth of mycorrhizal fungi, and (iii) induction of plant defence responses is not widespread among streptomycetes.