Species and organ specificity of fungal endophytes in herbaceous grassland plants

Abstract

Summary1. Foliar endophytic fungi in herbaceous plants are known to be diverse, yet studies characterizing the fungal communities in roots and shoots of plants across time are absent. These fungi are supposedly ubiquitous in nature, infecting plants through airborne spores. As many foliar endophytes can also exist in soil, we hypothesized that there would be a strong similarity between root and shoot endophytes in any given plant species and that differences between plant species would be greater than those between organs within a species. 2. Leaf and root fungal endophyte communities were assessed in field-collected plants of three co-occurring grassland forbs (Cirsium arvense, Plantago lanceolata and Rumex acetosa) in two contrasting seasons (winter and summer). The former two species are mycorrhizal, whilst the latter species is not so. 3. The highest fungal species richness was recorded from P. lanceolata with R. acetosa hosting the least endophyte diversity. Endophyte communities were more diverse in root than leaf tissues and in summer than in winter. Similarity of endophyte communities between different host plant species and organs within an individual host was very low. Negative correlations were found between mycorrhizal colonization and endophyte presence in the roots of C. arvense and P. lanceolata, suggesting some degree of antagonism or competition between the fungi. Consistent positive associations were found between the number of endophyte species in roots and shoots of plants. 4. Synthesis. In contrast to previous studies, the results show that many endophytes do not occur ubiquitously, but instead exhibit both plant and tissue specificity. There is a strong seasonal change in endophyte communities, but the differences between roots and shoots at any one time can be just as large. This dissimilarity suggests a lack of systemic growth by the fungi from one tissue to another. Mycorrhizas may interact negatively with other root endophytes, indicating that the latter should not be ignored in future mycorrhizal studies. We should begin to think of individual plants as ecosystems of interacting microbes, whose community is structured by plant genetics and environmental conditions, coupled with interactions between the microbes themselves.

Impact of a natural soil salinity gradient on fungal endophytes in wild barley (Hordeum maritimum With.)

“…It is also noteworthy that, in the present study, roots host higher diversity and were more frequently colonized by fungal endophytes than aboveground organs. Similar result has been obtained from studies on other halophytic (Kannan et al 2014) and non-halophytic (Wearn et al 2012) plants. The aboveground plant organs are exposed to stress factors such as UV radiation, desiccation and lack of nutrients (Lindow and Brandl 2003) that could account for the lower fungal diversity and colonization of leaves and twigs comparatively to roots.…”

“…(Fabaceae), and they found little similarity between these plant organs. Wearn et al (2012) also reported low similarity on endophytic fungal assemblages between roots and leaves of three cooccurring non-halophytes grassland forbs (Cirsium arvense, Plantago lanceolata and Rumex acetosa).…”

Entomopathogenic and Nematophagous Fungal Endophytes

“…In most of these surveys of natural plant hosts, nemato-and entomopathogens occur at a low frequency in populations of particular host plant species (i.e., Vázquez de Aldana et al 2013 ). However, exceptions to this occur, and a predominance of some species of these fungi has been reported in the endophytic mycobiota of some plant hosts (Miles et al 2012 ;Wearn et al 2012 ). Some entomopathogenic taxa have been identifi ed as natural endophytes in more than one host plant species (i.e., B. bassiana , Lecanicillium lecanii ) ( Growth promotion activities and their indirect effect on lower susceptibility to pest and diseases are represented in green , while direct protection against pest, pathogens, and nematodes are represented in red in general terms, a relatively common endophyte.…”

Are endophytes an important link between airborne spores and allergen exposure?

“…Therefore, considering the abundance of grasses on earth, and the apparently ubiquitous relationships of these fungi with grasses, these endophyte taxa can be considered important organisms in grass dominated ecosystems. Furthermore, some of these fungal genera have also been reported as dominant endophytes in leaves of dicotyledonous plant species, like Arabidopsis thaliana (García et al 2012), Vitis vinifera (González and Tello 2011), Cirsum arvense, Plantago lanceolata, Rumex acetosa (Wearn et al 2012), and others.…”