The arbuscular mycorrhizal fungi of Hyacinthoides non‐scripta I. Diversity of fungal taxa

Abstract

The arbuscular mycorrhizas of bluebell (Hyacinthoides non-scripta (L.) Chouard ex Rothm.) involve several symbiotic fungi of the order Glomales. We have previously simplified the system by ignoring the taxonomic diversity of the fungi, but it is unlikely that all fungal species contribute in the same manner or to the same extent to the functioning of the symbiosis. To discover how many and which fungi take part in the bluebell mycorrhiza we sought to identify the range of arbuscular mycorrhizal (AM) fungi found in bluebell roots sampled during a complete growing season, September to June.Although the taxonomy of the Glomales by their spores is not yet fully understood, identification is, to a large extent, possible. Arbuscular mycorrhizal communities are usually characterized by their spores but, since spores can rarely be directly associated with individual plants or plant species, a more satisfactory approach would be to identify fungal symbionts where they interact with the host plant, in the roots. Unfortunately, the intraradical mycelia of the fungi are less easily distinguished than the spores and, as yet, classification is possible only to the family level.We have developed a method whereby different AM fungal taxa in the roots of bluebell can be distinguished by objective assessment. A large suite of morphological characteristics of the fungi in roots was recorded in samples taken at monthly intervals. Hierarchical cluster analysis of the resulting data separated six distinct AM fungal morphotypes (Scutellospora type, Acaulospora type, three Glomus types and fine endophytes) and a classification system created by which identification by eye was possible.We compared the fungi in roots with glomalean spores in soil from the root zone of the same bluebell plants. Two species occurred in most samples, Scutellospora dipurpurescens Morton & Koske (emend. Walker, 1993) and Acaulospora koskei Blaskowski. A further six occurred sporadically, five Acaulospora spp. and Glomus rubiforme Gerdemann & Trappe) Almeida & Schenck ( l Sclerocystis rubiformis). The presence of a single species of Scutellospora was consistent with a Scutellospora root morphotype which varied little. By contrast, the diversity of Acaulospora in the spore assemblage was reflected by variation within the Acaulospora morphotype. Glomus spores were very rarely found in field collections, yet Glomus morphotypes were found to be an important component of the bluebell mycorrhiza.Because some important species are not represented in spore assemblages in the field and those that are found can only be associated with vegetational groups, not individual plants or single species, glomalean spore populations provide only a partial account of the fungi which contribute to arbuscular mycorrhizas. Although it is still not possible to identify AM fungi in roots with the same precision as their spores, the method reported here permits assessment of diversity in the roots of individual plant species, which may be applied to the investigation of mycorrhi...

Relative roles of niche and neutral processes in structuring a soil microbial community

“…AM fungi are obligate plant-root endosymbionts that colonize approximately 2/3 of terrestrial plant species, acquire all their carbon from the host plant and deliver to the plant a range of beneficial impacts, notably increased phosphorus uptake, and thus have profound effects on plant community dynamics and diversity (Fitter, 2005;Rosendahl, 2008). AM fungal species cannot be identified morphologically in roots (Merryweather and Fitter, 1998) and to overcome these problems DNA-based techniques have been developed that quantify fungi from plant roots collected from natural systems (Helgason et al, 1998). However, most DNA-based studies have either compared AM fungal diversity between habitats or simply listed species (see Ö pik et al, 2006 for a review).…”

Diversity and classification of mycorrhizal associations

“…Substantial variations in the growth patterns of hyphae associated with particular VAM fungi should be referred to as 'morphotypes' (Abbott, 1982 ;Brundrett et al, 1996;Merryweather & Fitter, 1998). Major VAM morphotypes are listed in Fig.…”

The arbuscular mycorrhizal fungi of Hyacinthoides non‐scripta II. Seasonal and spatial patterns of fungal populations

“…are colonized by a range of fungal symbionts from several genera of the order Glomales. Using the identification scheme described in Merryweather & Fitter (1998), arbuscular mycorrhizal (AM) fungi in bluebell roots were quantified throughout the single growing season of 1994-5 and compared with populations of spores found in the soil around the roots.In the early part of the growing season, when its activity is entirely subterranean (autumn and winter), bluebell habitually associates with a Scutellospora morphotype which is almost certainly S. dipurpurescens Morton & Koske (emend. Walker, 1993) whose spores occur in the root zone.…”