Xylariales): Physiological characterization and structural features of its association with wheat.

Abstract

Summary: Plant roots can be colonized by asymptomatic fungal strains belonging to several taxa, among them, the group defined as Dark Septate Endophytes (DSE). Microdochium bolleyi commonly colonizes wheat roots and other crops. It is considered a weak pathogen or even a non-pathogenic fungal species, which has also been considered as a potential biocontrol agent against aggressive soil-borne pathogens in cereal crops. We isolated a strain of M. bolleyi from wheat roots sampled in a crop field in Argentina, and characterized its abilities to grow in different carbon and nitrogen sources, to produce indole and to solubilize phosphorus; also several enzymatic activities were evaluated. In addition, resynthesis was performed under controlled conditions in order to characterize root fungal colonization under both, optical and transmission microscopy. The strain 22-1 colonized wheat root parenchymal tissue, forming chlamysdospores inside parenchymal cells and root hairs, and poorly grew in carbon and nitrogen sources. This fungus also synthesized indoles in in vitro culture, but it cannot solubilize phosphorus. Only amylase activity was detected out of seven enzymatic activity measured. Microdochium bolleyi (strain 22-1) colonized the roots, it formed typical DSE fungal structures and behaved like a "true endophyte"; however further studies are necessary to elucidate its role in the association with wheat.Key words: Dark septate endophytes, Microdochium bolleyi, root endophytes, wheat crop.Resumen: Microdochium bolleyi (Ascomycota: Xylariales): Caracterización fisiológica y caracteres estructurales de su asociación con trigo. Las raíces de las plantas hospedan una gran diversidad de hongos, entre ellos, se encuentran los Endofitos Septados Oscuros (ESO). Microdochium bolleyi coloniza las raíces de trigo y otros cereales, aunque algunos autores lo han considerado un patógeno débil, otros han demostrado su acción biocontroladora contra patógenos agresivos del suelo. En el presente trabajo, se aisló una cepa de M. bolleyi (22-1) de raíces de trigo. Esta cepa fue metabólicamente caracterizada y se realizó un ensayo de resíntesis bajo condiciones controladas con el fin de caracterizar la colonización del hongo en la raíz bajo microscopía óptica y de transmisión. Su crecimiento fue escaso en las fuentes de carbono y nitrógeno evaluadas, sintetizó indoles en cultivo in vitro, pero no mostró habilidades para solubilizar el fósforo, por último, solo se detectó actividad amilasa. La cepa 22-1 coloniza la corteza radicular del trigo, formando clamidosporas melanizadas inter e intracelularmente y en el interior de los pelos radiculares. Microdochium bolleyi (cepa 22-1) coloniza la raíz de trigo formando las típicas estructuras de los ESO y comportándose como un "verdadero endófito", sin embargo, se necesitan más estudios para terminar de dilucidar su papel en la asociación con el trigo.Palabras clave: Endofitos septados oscuros, hongos endofitos, Microdochium bolleyi, trigo.

The Potential of Rhizoctonia-Like Fungi for the Biological Protection of Cereals against Fungal Pathogens

“…Infestation with this pathogen allows other fungi to colonize host tissues, include highly virulent pathogens represented by F. culmorum , or other weaker or non-pathogenic species of fungi such as Microdochium bolleyi [ 41 ]. M. bolleyi can be considered as a potential biocontrol agent against aggressive soil-borne pathogens in cereal crops [ 42 ].…”

Rye Snow Mold-Associated Microdochium nivale Strains Inhabiting a Common Area: Variability in Genetics, Morphotype, Extracellular Enzymatic Activities, and Virulence

“…However, the enzymes that are considered as major PCWDEs (cellulases, xylanases, pectinases, proteases, and lignin peroxidases) have not been analyzed for the members of Microdochium genus. The only extracellular enzymatic activities described for Microdochium species are amylase and invertase (non-PCWDEs) and glucosidase and galactosidase ("minor" PCWDEs) [44,74,141]. In our study, we showed that, in addition to extracellular amylase and invertase, Microdochium strains produce extracellular cellulase (endoglucanase), protease, lignin peroxidase, xylanase, arabinofuranosidase, and pectate lyase.…”

First genome-scale insights into the virulence of the snow mold causal fungus Microdochium nivale

“…Second, it is possible that the deferential pathogenicity of M. nivale and M. bolleyi is determined not by the set of virulence factors but by the regulatory networks coordinating their production. Third, although M. bolleyi has been described as a non-phytopathogenic root endophyte (Rothen et al 2018 ), it cannot be ruled out that, under specific conditions, it is also able to cause disease and thus manifest phytopathogenicity.…”

“…Orthologous groups of proteins were identified using OrthoFinder with default settings. The orthologs were searched in the reference proteomes of M. nivale and three other Ascomycota species, M. bolleyi , Sclerotinia borealis , and Fusarium graminearum with contrasting lifestyles: M. bolleyi is a non-psychrotolernat and non-phytopathogenic species (Rothen et al 2018 ), S. borealis is a snow mold-causing psychrophilic species (Hoshino et al 2010 ), and F. graminearum is a mesophilic head blight causal agent (Goswami and Kistler 2004 ).…”