Inoculation with arbuscular mycorrhizal fungi (AMF) may improve plant performance at disturbed sites, but inoculation may also suppress root colonization by native AMF and decrease the diversity of the root-colonizing AMF community. This has been shown for the roots of directly inoculated plants, but little is known about the stability of inoculation effects, and to which degree the inoculant and the inoculation-induced changes in AMF community composition spread into newly emerging seedlings that were not in direct contact with the introduced propagules. We addressed this topic in a greenhouse experiment based on the soil and native AMF community of a post-mining site. Plants were cultivated in compartmented pots with substrate containing the native AMF community, where AMF extraradical mycelium radiating from directly inoculated plants was allowed to inoculate neighboring plants. The abundances of the inoculated isolate and of native AMF taxa were monitored in the roots of the directly inoculated plants and the neighboring plants by quantitative real-time PCR. As expected, inoculation suppressed root colonization of the directly inoculated plants by other AMF taxa of the native AMF community and also by native genotypes of the same species as used for inoculation. In the neighboring plants, high abundance of the inoculant and the suppression of native AMF were maintained. Thus, we demonstrate that inoculation effects on native AMF propagate into plants that were not in direct contact with the introduced inoculum, and are therefore likely to persist at the site of inoculation.

• MeSH
• Genotype MeSH
• Plant Roots microbiology   MeSH
• Mycelium growth & development   MeSH
• Mycorrhizae growth & development   MeSH
• Soil MeSH
• Plants microbiology   MeSH
• Seedlings microbiology   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Soil MeSH

Communities of arbuscular mycorrhizal fungi (AMF) are crucial for promoting plant productivity in most terrestrial systems, including anthropogenically managed ecosystems. Application of AMF inocula has therefore become a widespread practice. It is, however, pertinent to understand the mechanisms that govern AMF community composition and their performance in order to design successful manipulations. Here we assess whether the composition and plant growth-promotional effects of a synthetic AMF community can be altered by inoculum additions of the isolates forming the community. This was determined by following the effects of three AMF isolates, each inoculated in two propagule densities into a preestablished AMF community. Fungal abundance in roots and plant growth were evaluated in three sequential harvests. We found a transient positive response in AMF abundance to the intraspecific inoculation only in the competitively weakest isolate. The other two isolates responded negatively to intra- and interspecific inoculations, and in some cases plant growth was also reduced. Our results suggest that increasing the AMF density may lead to increased competition among fungi and a trade-off with their ability to promote plant productivity. This is a key ecological aspect to consider when introducing AMF into soils.

• MeSH
• DNA, Fungal chemistry   genetics   MeSH
• Fungi classification   genetics   growth & development   MeSH
• Plant Roots microbiology   MeSH
• Molecular Sequence Data MeSH
• Mycorrhizae classification   genetics   growth & development   MeSH
• Colony Count, Microbial MeSH
• Sequence Analysis, DNA MeSH
• Biota * MeSH
• Plant Development MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Fungal MeSH

During the last decade, the application of arbuscular mycorrhizal fungi (AMF) as bioenhancers has increased significantly. However, until now, it has been difficult to verify the inoculation success in terms of fungal symbiont establishment in roots of inoculated plants because specific fungal strains could not be detected within colonized roots. Using mitochondrial large subunit ribosomal DNA, we show that Rhizophagus irregularis (formerly known as Glomus intraradices) isolate BEG140 consists of two different haplotypes. We developed nested PCR assays to specifically trace each of the two haplotypes in the roots of Phalaris arundinacea from a field experiment in a spoil bank of a former coal mine, where BEG140 was used as inoculant. We revealed that despite the relatively high diversity of native R. irregularis strains, R. irregularis BEG140 survived and proliferated successfully in the field experiment and was found significantly more often in the inoculated than control plots. This work is the first one to show tracing of an inoculated AMF isolate in the roots of target plants and to verify its survival and propagation in the field. These results will have implications for basic research on the ecology of AMF at the intraspecific level as well as for commercial users of mycorrhizal inoculation.

• MeSH
• DNA, Fungal genetics   MeSH
• Phylogeny MeSH
• Genetic Markers MeSH
• Glomeromycota genetics   isolation & purification   physiology   MeSH
• Haplotypes MeSH
• Plant Roots microbiology   MeSH
• DNA, Mitochondrial genetics   MeSH
• Mitochondria genetics   MeSH
• Molecular Sequence Data MeSH
• Mycorrhizae genetics   isolation & purification   physiology   MeSH
• Phalaris microbiology   physiology   MeSH
• Polymerase Chain Reaction methods   MeSH
• Soil Microbiology MeSH
• DNA, Ribosomal genetics   MeSH
• Base Sequence MeSH
• Sequence Analysis, DNA MeSH
• Sequence Alignment MeSH
• Symbiosis MeSH
• Coal Mining MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Czech Republic MeSH
• Names of Substances
• DNA, Fungal MeSH
• Genetic Markers MeSH
• DNA, Mitochondrial MeSH
• DNA, Ribosomal MeSH