All plants are inhabited internally by diverse microbial communities comprising bacterial, archaeal, fungal, and protistic taxa. These microorganisms showing endophytic lifestyles play crucial roles in plant development, growth, fitness, and diversification. The increasing awareness of and information on endophytes provide insight into the complexity of the plant microbiome. The nature of plant-endophyte interactions ranges from mutualism to pathogenicity. This depends on a set of abiotic and biotic factors, including the genotypes of plants and microbes, environmental conditions, and the dynamic network of interactions within the plant biome. In this review, we address the concept of endophytism, considering the latest insights into evolution, plant ecosystem functioning, and multipartite interactions.

The Hidden World within Plants: Ecological and Evolutionary Considerations for Defining Functioning of Microbial Endophytes

The results of analyses of the distribution, structure and function of ericoid, ecto and vesicular-arbuscular mycorrhizas are used to challenge the conventional view, which was based largely upon studies of isolated plants and excised plant roots under controlled conditions, that the symbiosis is primarily involved in the capture of phosphate ions. In nature, each mycorrhizal type is associated with an ecosystem and soil environment with distinctive characteristics in which selection has favoured the development of a particular range of attributes. These attributes are evaluated and their importance for the individual plant and for the ecosystems in which they occur is assessed. It is concluded that knowledge of the full range of functions of each mycorrhizal type is essential for an understanding of the distribution and dynamics of the ecosystem in which it predominates.

Mycorrhizas in ecosystems

▪ Abstract Endophytic fungi living asymptomatically within plant tissues have been found in virtually all plant species. Endophytes are considered plant mutualists: They receive nutrition and protection from the host plant while the host plant may benefit from enhanced competitive abilities and increased resistance to herbivores, pathogens, and various abiotic stresses. Limited evidence also indicates that endophytes may influence population dynamics, plant community diversity, and ecosystem function. However, most of the empirical evidence for this mutualism and its ecological consequences has been based on a few agronomic grass endophytes. More recent studies suggest that endophyte-host plant interactions are variable and range from antagonistic to mutualistic. A more comprehensive view of the ecology and evolution of endophytes and host plants is needed. This article discusses how life history traits—such as fungal reproduction and pattern of infections and genotypic variation and ecological factors—in...

https://www.jstor.org/stable/pdfplus/221711.pdf

FUNGAL ENDOPHYTES: A Continuum of Interactions with Host Plants

Dark septate root endophytes (DSE) are conidial or sterile fungi (Deuteromycotina, Fungi Imperfecti) likely to be ascomycetous and colonizing plant roots. They have been reported for nearly 600 plant species representing about 320 genera and 100 families. DSE fungi occur from the tropics to arctic and alpine habitats and comprise a heterogeneous group that functionally and ecologically overlaps with soil fungi, saprotrophic rhizoplane-inhabiting fungi, obligately and facultatively pathogenic fungi and mycorrhizal fungi. Numerous species of undescribed sterile and anamorphic taxa may also await discovery. Although DSE are abundant in washed root and soil samples from various habitats, and are easily isolated from surface-sterilized roots of ecto-, ectendo-, endo- and non-mycorrhizal host species, their ecological functions are little understood. Studies of DSE thus far have yielded inconsistent results and only poorly illustrate the role of DSE in their natural habitats. These inconsistencies are largely due to the uncertain taxonomic affinities of the strains of DSE used. In addition, because different strains of a single anamorph taxon seem to vary greatly in function, no clear generalizations on their ecological role have been drawn. This paper reviews the current literature on DSE and the ecology and discusses the need for and direction of future research.

Dark septate endophytes: a review of facultative biotrophic root-colonizing fungi

The ectomycorrhizal (EcM) symbiosis involves a large number of plant and fungal taxa worldwide During studies on EcM diversity, numerous misidentifications, and contradictory reports on EcM status have been published This review aims to: (1) critically assess the current knowledge of the fungi involved in the EcM by integrating data from axenic synthesis trials, anatomical, molecular, and isotope studies; (2) group these taxa into monophyletic lineages based on molecular sequence data and published phylogenies; (3) investigate the trophic status of sister taxa to EcM lineages; (4) highlight other potentially EcM taxa that lack both information on EcM status and DNA sequence data; (5) recover the main distribution patterns of the EcM fungal lineages in the world Based on critically examining original reports, EcM lifestyle is proven in 162 fungal genera that are supplemented by two genera based on isotopic evidence and 52 genera based on phylogenetic data Additionally, 33 genera are highlighted as potentially EcM based on habitat, although their EcM records and DNA sequence data are lacking Molecular phylogenetic and identification studies suggest that EcM symbiosis has arisen independently and persisted at least 66 times in fungi, in the Basidiomycota, Ascomycota, and Zygomycota The orders Pezizales, Agaricales, Helotiales, Boletales, and Cantharellales include the largest number of EcM fungal lineages Regular updates of the EcM lineages and genera therein can be found at the UNITE homepage http://uniteutee/EcM_lineages The vast majority of EcM fungi evolved from humus and wood saprotrophic ancestors without any obvious reversals Herbarium records from 11 major biogeographic regions revealed three main patterns in distribution of EcM lineages: (1) Austral; (2) Panglobal; (3) Holarctic (with or without some reports from the Austral or tropical realms) The holarctic regions host the largest number of EcM lineages; none are restricted to a tropical distribution with Dipterocarpaceae and Caesalpiniaceae hosts We caution that EcM-dominated habitats and hosts in South America, Southeast Asia, Africa, and Australia remain undersampled relative to the north temperate regions In conclusion, EcM fungi are phylogenetically highly diverse, and molecular surveys particularly in tropical and south temperate habitats are likely to supplement to the present figures Due to great risk of contamination, future reports on EcM status of previously unstudied taxa should integrate molecular identification tools with axenic synthesis experiments, detailed morphological descriptions, and/or stable isotope investigations We believe that the introduced lineage concept facilitates design of biogeographical studies and improves our understanding about phylogenetic structure of EcM fungal communities

Ectomycorrhizal lifestyle in fungi: global diversity, distribution, and evolution of phylogenetic lineages

Mycorrhizal fungi of a timber species, Pinus radiata D. Don, exotic to New Zealand were isolated. Two isolation methods were used, and root washing without surface sterilization was found to produce a higher proportion of mycorrhizal fungi. Mycorrhizal roots were plated out on Hagem medium and from 7000 pieces 32% yielded Rhizopogon spp; 3% gave rise to Amanita muscaria (L. ex Fr.) S.F. Gray, Hebeloma crustuliniforme (Bull. ex St. Am.) Quel., Suillus spp, Thelephora terrestris Ehrh. ex Fr., and unidentified basidiomycetes; 14% yielded dark sterile mycelia; 19% were sporing Fungi Imperfecti presumed to be contaminants; and 32% remained free of fungal outgrowth. Some of the fungi commonly occurring in P. radiata stands, such as Laccaria laccata (Scop. ex Fr.) Berk. & Br. and Scleroderma verrucosum Vaill. ex Pers. and generally supposed to be mycorrhizal associates of this tree species, were not isolated even though they grow well on the media used for isolation.

Mycorrhizas were synthesized on P. radiata seedlings by 16 basidiomycete fungi but under the test conditions Boletus piperatus (Bull. ex Fr.) O. Kuntze and Inocyhe sp., commonly assumed to be mycorrhiza formers on this tree species, did not form mycorrhizas.

The results indicate Rhizopogon spp are a major component of mycorrhiza formers isolated from P. radiata in New Zealand.

Mycorrhizal fungi of Pinus radiata in New Zealand.

Propagule population densities of the nine mycorrhizal species detected in field plots planted to tall fescue free of the Acremonium coenophialum endophyte were more than double those in plots planted to fescue heavily infected with Acremonium . Seedlings of Acremonium -free fescue detected more propagules of most of the eleven mycorrhizal species detected in a field soil than seedlings infected with Acremonium . Sporulation by three mycorrhizal isolates over 17 weeks was higher on fescue seedlings free of Acremonium than on seedlings infected with Acremonium . Since mycorrhizal fungi are believed to be confined to roots and Acremonium endophytes to shoots, the inhibitory effect of Acremonium on mycorrhizal fungi may be due to the translocation to roots of alkaloids produced by the Acremonium-Festuca symbiosis.

Suppression of mycorrhizal fungi in fescue by the acremonium coenophialum endophyte

Fungal sporocarps of Hydnangium carneum Wallr., Laccaria laccata (Scop. ex Fr.) Berk. ex Br., Scleroderma spp, Hymenogaster spp., Hysterangium spp, Cortinarius spp, etc. were found to be associated with five species of eucalypts Eucalyptus delegatensis R.T. Bak., E. regnans F. Muell., E. nitens Maiden, E.fastigata Deane et Maiden, and E. saligna Sm.) in nurseries or stands in the North Island of New Zealand. A total of 5345 mycorrhizal pieces were plated out in isolation studies. More than 47% of these pieces remained free of fungal outgrowth, 16% yielded dark sterile mycelia, 7% yielded hyaline sterile fungi, 17% produced sporing Fungi Imperfecti, 5.8% were basidiomycetous fungi identified as H. carneum, Scleroderma spp, Paxillus sp. and Hymenogaster albus (Klotzsch) Berk. et Br., and 5.9% were unidentified basidiomycetes. Mycorrhizas were synthesized on eucalypt seedlings by 12 identified basidiomycetes which form sporocarps in eucalypt stands and 12 unidentified basidiomycetes isolated from the mycorrhizas. Under the test conditions two Cortinarius spp and one unidentified basidiomycete did not form mycorrhizas. The results indicate a possible importance of H. carneum as a mycorrhizal fungus of eucalypts in the North Island of New Zealand.

Mycorrhizal fungi of Eucalyptus in the North Island of New Zealand

Mycorrhizal fungi of radiata pine (Pinus radiata D. Don) planted in forests established on different soil types (sand, pumice-scoria and clay) located in the North and South Islands of New Zealand were studied. There were no major differences in the mycorrhizal fungal species between the forests in the North and South Islands and the most common mycorrhizal fungi were Rhizopogon rubescens Tul. and Suillus luteus (L. ex. Fr.) S.F. Gray. The different soil types did affect the number of myocrrhizal fungal species and the abundance of sporocarps of this fungi. The largest number of fungal species were found in forests established on pumice-scoria.

Mycorrhizal fungi of radiata pine in different forests of the north and south islands in New Zealand

Thirteen types of natural Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) mycorrhizas were characterized and nine of them were identified as P. menziesii + Rhizopogon sp., P. menziesii + R. vinicolor, P. menziesii + Hebeloma crustuliniforme, P. menziesii + Amanita muscaria, P. menziesii + Endogone flammicorona, P. menziesii + Boletus sp., P. menziesii + Laccaria laccata, P. menziesii + Thelephora terrestris and P. menziesii+Tuber sp.

Myra Chu-Chou

Papers

Mycorrhizal fungi of Pinus radiata in New Zealand.

Suppression of mycorrhizal fungi in fescue by the acremonium coenophialum endophyte

Mycorrhizal fungi of Eucalyptus in the North Island of New Zealand

Mycorrhizal fungi of radiata pine in different forests of the north and south islands in New Zealand

Characterization and identification of mycorrhizas of Douglas fir in New Zealand