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Dark septate endophytes (DSEs) are widely distributed worldwide and can promote plant growth. Therefore, they are considered potentially important plant allies, especially in stressful environments. Previous studies have reported that DSEs cohabit roots with other microorganisms such as ectomycorrhizal (ECM), endophytic and pathogenic fungi/oomycetes. However, interactions between different DSE species have not yet been reported, and studies on the interactions between DSEs and other fungi are scarce. Using a simple and reproducible pairwise growth assay in vitro, we studied the synergistic/antagonistic interactions between eight DSEs, two ECM fungi and three root pathogens. Most of the DSE/DSE outcomes were neutral. Interestingly, we identified several DSE strains acting in synergy with other strains, as well as strains that could potentially act as biocontrol agents. Notably, three metal-tolerant DSE strains, namely, Cadophora sp., Leptodontidium sp. and Phialophora mustea, could decrease the growth of the root phytopathogens Pythium intermedium, Phytophthora citricola and Heterobasidion annosum. The present data are discussed in the general context of the use of fungal consortia as inocula in the tree-based phytomanagement of marginal lands.

An interaction study was performed with mycorrhizal plants of the grapevine rootstock Richter 110 (Vitis berlandieri Planch × Vitis rupestris Scheele) and the root pathogenic fungus Armillaria mellea (Vahl:Fr.) P. Kumm using an autotrophic in vitro culture system. Micropropagated plantlets were transferred to Petri plates with MSR medium lacking sugar and vitamins. Inocula of Glomus intraradices (BEG 72) and of Armillaria mellea obtained from a root organ culture and from a mycelium colony grown in malt agar respectively, were added to the plates according to each treatment: non-inoculated, inoculated with G. intraradices, inoculated with A. mellea, and dual-inoculated plants. There were ten replicates per treatment. Fourteen weeks later, the pathogen's mycelium occupied most of the surface/volume of the plate and had produced rhizomorphs. In dual inoculated plates, A. mellea's growth was not affected by the presence of G. intraradices, but the latter produced a lower number of spores and its extraradical phase showed granulation, vacuolation and tip swelling. The pathogen induced necrosis and growth decrease in the root. Glomus intraradices alleviated these symptoms and there were no differences in root biomass between non-inoculated plants and plants inoculated with both fungi. There were no symptoms of the disease in shoots and G. intraradices stimulated shoot growth both, although mycorrhizal colonization was lower when A. mellea was present. No direct antagonism or antibiosis against the pathogen was observed, thus the protective effect exerted by the symbiotic fungus in grapevines must be indirect, mediated through the host plant physiology., Se estudió la interacción entre plantas micorrizadas del portainjerto de vid 110 Richter (Vitis berlandieri Planch × Vitis rupestris Scheele) y Armillaria mellea (Vahl:Fr.) P. Kumm en cultivo autotrófico in vitro. Plantas micropropagadas fueron transferidas a placas de Petri con medio MSR sin azúcar ni vitaminas. Inóculo de Glomus intraradices Schenck and Smith (BEG 72) obtenido a partir de un cultivo axénico de raíces transformadas micorrizadas, e inóculo de A. mellea obtenido en medio agar-malta, se añadieron a las placas según tratamiento: no inoculado, inoculación con G. intraradices, inoculación con A. mellea e inoculación combinada, estableciéndose 10 réplicas por tratamiento. Catorce semanas después, el micelio del hongo patógeno ocupaba casi la totalidad de la superficie/volumen de la placa y había producido rizomorfos. En placas con inoculación mixta, el desarrollo de A. mellea no se vio afectado por la presencia de G. intraradices, mientras que éste produjo menos esporas, y su fase extraradical presentaba granulaciones, vacuolaciones y engrosamientos en las terminaciones. El patógeno indujo necrosis y menor desarrollo radical. Glomus intraradices alivió estos síntomas, y no se observaron diferencias entre la biomasa radical de plantas no inoculadas y de plantas inoculadas con ambos hongos. No aparecieron síntomas de la enfermedad en la parte aérea y G. intraradices estimuló en cualquier caso el crecimiento, pero la colonización micorrícica fue menor en presencia del patógeno. No se observó antagonismo directo o antibiosis, el efecto de protección de la simbiosis micorrícica en vid frente a A. mellea debe ser indirecto, a través de la fisiología del hospedador.

An interaction study was performed with mycorrhizal plants of the grapevine rootstock Richter 110 (Vitis berlandieri Planch × Vitis rupestris Scheele) and the root pathogenic fungus Armillaria mellea (Vahl:Fr.) P. Kumm using an autotrophic in vitro culture system. Micropropagated plantlets were transferred to Petri plates with MSR medium lacking sugar and vitamins. Inocula of Glomus intraradices (BEG 72) and of Armillaria mellea obtained from a root organ culture and from a mycelium colony grown in malt agar respectively, were added to the plates according to each treatment: non-inoculated, inoculated with G. intraradices, inoculated with A. mellea, and dual-inoculated plants. There were ten replicates per treatment. Fourteen weeks later, the pathogen's mycelium occupied most of the surface/volume of the plate and had produced rhizomorphs. In dual inoculated plates, A. mellea's growth was not affected by the presence of G. intraradices, but the latter produced a lower number of spores and its extraradical phase showed granulation, vacuolation and tip swelling. The pathogen induced necrosis and growth decrease in the root. Glomus intraradices alleviated these symptoms and there were no differences in root biomass between non-inoculated plants and plants inoculated with both fungi. There were no symptoms of the disease in shoots and G. intraradices stimulated shoot growth both, although mycorrhizal colonization was lower when A. mellea was present. No direct antagonism or antibiosis against the pathogen was observed, thus the protective effect exerted by the symbiotic fungus in grapevines must be indirect, mediated through the host plant physiology. Se estudió la interacción entre plantas micorrizadas del portainjerto de vid 110 Richter (Vitis berlandieri Planch × Vitis rupestris Scheele) y Armillaria mellea (Vahl:Fr.) P. Kumm en cultivo autotrófico in vitro. Plantas micropropagadas fueron transferidas a placas de Petri con medio MSR sin azúcar ni vitaminas. Inóculo de Glomus intraradices Schenck and Smith (BEG 72) obtenido a partir de un cultivo axénico de raíces transformadas micorrizadas, e inóculo de A. mellea obtenido en medio agar-malta, se añadieron a las placas según tratamiento: no inoculado, inoculación con G. intraradices, inoculación con A. mellea e inoculación combinada, estableciéndose 10 réplicas por tratamiento. Catorce semanas después, el micelio del hongo patógeno ocupaba casi la totalidad de la superficie/volumen de la placa y había producido rizomorfos. En placas con inoculación mixta, el desarrollo de A. mellea no se vio afectado por la presencia de G. intraradices, mientras que éste produjo menos esporas, y su fase extraradical presentaba granulaciones, vacuolaciones y engrosamientos en las terminaciones. El patógeno indujo necrosis y menor desarrollo radical. Glomus intraradices alivió estos síntomas, y no se observaron diferencias entre la biomasa radical de plantas no inoculadas y de plantas inoculadas con ambos hongos. No aparecieron síntomas de la enfermedad en la parte aérea y G. intraradices estimuló en cualquier caso el crecimiento, pero la colonización micorrícica fue menor en presencia del patógeno. No se observó antagonismo directo o antibiosis, el efecto de protección de la simbiosis micorrícica en vid frente a A. mellea debe ser indirecto, a través de la fisiología del hospedador.