Seasonal Dynamics of Arbuscular Mycorrhizal Fungal Communities in Roots in a Seminatural Grassland

Abstract

Symbiotic arbuscular mycorrhizal fungi (AMF) have been shown to influence both the diversity and productivity of grassland plant communities. These effects have been postulated to depend on the differential effects of individual mycorrhizal taxa on different plant species; however, so far there are few detailed studies of the dynamics of AMF colonization of different plant species. In this study, we characterized the communities of AMF colonizing the roots of two plant species, Prunella vulgaris and Antennaria dioica, in a Swedish seminatural grassland at different times of the year. The AMF small subunit rRNA genes were subjected to PCR, cloning, sequencing, and phylogenetic analysis. Nineteen discrete sequence types belonging to Glomus groups A and B and to the genus Acaulospora were distinguished. No significant seasonal changes in the species compositions of the AMF communities as a whole were observed. However, the two plant species hosted significantly different AMF communities. P. vulgaris hosted a rich AMF community throughout the entire growing season. The presence of AMF in A. dioica decreased dramatically in autumn, while an increased presence of Ascomycetes species was detected.In temperate and boreal regions, seminatural grasslands are some of the most species-rich plant communities (37). Grasslands in Europe have been managed during the last millennia by grazing and haymaking. The total area and connectivity of grasslands have decreased dramatically during the last hundred years (77). This decline is one of the major threats to diversity for many groups of organisms (44).Arbuscular mycorrhizal fungi (AMF), belonging to the phylum Glomeromycota, are obligate symbiotic fungi forming mutualistic associations with the roots of most land plants. Increased access to low-mobility soil mineral nutrients has been considered to be the main beneficial effect of AMF on their host plants (61). Experimental greenhouse studies have shown that AMF diversity can affect the diversity and productivity of the host plant communities and, therefore, the functioning of the whole ecosystem (21,33,74,76,78). Other benefits to host plants arising from the presence of AMF include a reduction in the occurrence of pathogenic infections (5, 41), the improvement of water relations (9), and the limitation of heavy-metal uptake (39). The effects of AMF diversity and species composition are thought to arise through differential effects of different AMF taxa on the growth of individual plant species (47), but descriptive ecological data on the structure of AMF communities are still few in comparison with the available information on the structure and dynamics of plant communities (52).Investigations of the phenology, diversity, and functioning of natural AMF communities have traditionally been based on root colonization estimates and spore counts. The extension of the intraradical mycelia gives information on the mycorrhizal status of the plant but can provide hardly any information about the identities of the fungi. Soil spore anal...

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“…0.03% of reads (53 OTU) were from Glomeromycota. Glomeromycota is the phylum that most arbuscular mycorrhizal fungi belong to and was previously reported to be dominant in grasslands (63) and widespread among different global ecosystems (64). Since a previous study using the same primer set identified at least 15% Glomeromycota in an Oklahoma tallgrass prairie soil, the low relative abundance of Glomeromycota identified here did not arise from the primer set used for PCR amplification, which was also verified by the NCBI primer tool (60).…”

Dioecious species and arbuscular mycorrhizal symbioses: The case ofAntennaria dioica

“…This is consistent with a previous study where the AM fungal genera colonizing the roots of A. dioica were characterized with molecular methods: 14 sequence types belonging to genera Glomus and Acaulospora were identified inside the roots of A. dioica plants collected in central Sweden. 9 Even though the sex of the Swedish plants was not specified, the authors also analyzed seasonal dynamics in community composition and reported the highest diversity of sequence types in May and June, 9 exactly when we also observed the highest percentage of colonization by arbuscules and the plants had flowers. 14 In autumn the diversity of sequence types decreased 9 in line with our finding of declining AM colonization frequency toward the end of the growing season (Fig.…”

“…In terms of the frequency of arbuscules, there were significant interactions between the interaction between AM fungi and plants is more complex, 3,11 the plants are colonized by several AM fungal species and the colonization can be species-specific. 9 The AM fungal species that A. dioica associates with under natural conditions are unknown. In this paper, we also report AM fungal species associated to the rhizosphere of A. dioica in the three populations in central Finland.…”

“…However, the outcome of the relationship may vary along a continuum from mutualism to parasitism depending on biotic and abiotic factors, [5][6][7] the symbiont identity, 7 and the AM colonization frequency in the roots. 8 Typically, plants are colonized by multiple fungal species 9 and the same fungus can simultaneously colonize different plants. Given that plants and their mycorrhizal symbionts can detect and preferentially reward the most beneficial partner, 10 and that the sexes in dioecious species usually differ in resource needs and allocation patterns, 1,2 it is logical to predict that the sexes in dioecious plants could differ in the cost-benefit of this symbiosis.…”

Effects of different management practices on arbuscular mycorrhizal fungal diversity in maize fields by a molecular approach

“…The universal eukaryotic primer NS31 (Simon et al 1992) was used as the forward primer for the first primer set. A mixture of three different primers (AMmix) was used as the reverse primer-AM1 (Helgason et al 1998), AM2 and AM3 (Santos-González et al 2007) primers-designed to amplify ∼550-bp fragments of partial SSU rDNA. The second primer set (28G1-28G2) was designed to amplify a ∼600-bp fragment of partial LSU rDNA (da Silva et al 2006).…”