Options of partners improve carbon for phosphorus trade in the arbuscular mycorrhizal mutualism

Argüello, Alicia; O’Brien, Michael J.; Heijden, Marcel G. A. van der; Wiemken, Andres; Schmid, Bernhard; Niklaus, Pascal A.

doi:10.1111/ele.12601

Cited by 68 publications

(56 citation statements)

References 32 publications

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“…For instance, Argüello et al . () found that diversity of AMF promotes cooperation between plants and AMF. However, promoting diversity and inoculum density of AMF may trade‐off their ability to stimulate plant productivity in some instances.…”

Section: Fungal Genotypementioning

confidence: 99%

Little evidence that farmers should consider abundance or diversity of arbuscular mycorrhizal fungi when managing crops

2018

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Contents Summary 1092 I. Introduction 1093 II. Investigating activity of AMF in agroecosystems 1093 III. Crop benefit from AMF: agronomic and mycorrhizal literature differ 1094 IV. Flawed methodology leads to benefits of mycorrhizas being overstated 1094 V. Rigorous methodology suggests low colonisation by AMF can sometimes reduce crop yield 1095 VI. Predicting when mycorrhizas matter for crop yield 1096 VII. Crop genotype 1099 VIII. Fungal genotype 1100 IX. Complex interactions between the mycorrhizal fungal and soil microbial communities 1102 X. Phosphorus-efficient agroecosystems 1102 XI. Conclusions 1103 Acknowledgements 1104 References 1104 SUMMARY: Arbuscular mycorrhizal fungi (AMF) are ubiquitous in agroecosystems and often stated to be critical for crop yield and agroecosystem sustainability. However, should farmers modify management to enhance the abundance and diversity of AMF? We address this question with a focus on field experiments that manipulated colonisation by indigenous AMF and report crop yield, or investigated community structure and diversity of AMF. We find that the literature presents an overly optimistic view of the importance of AMF in crop yield due, in part, to flawed methodology in field experiments. A small body of rigorous research only sometimes reports a positive impact of high colonisation on crop yield, even under phosphorus limitation. We suggest that studies vary due to the interaction of environment and genotype (crop and mycorrhizal fungal). We also find that the literature can be overly pessimistic about the impact of some common agricultural practices on mycorrhizal fungal communities and that interactions between AMF and soil microbes are complex and poorly understood. We provide a template for future field experiments and a list of research priorities, including phosphorus-efficient agroecosystems. However, we conclude that management of AMF by farmers will not be warranted until benefits are demonstrated at the field scale under prescribed agronomic management.

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Section: Fungal Genotypementioning

confidence: 99%

Little evidence that farmers should consider abundance or diversity of arbuscular mycorrhizal fungi when managing crops

2018

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“…In general, the extent to which one partner or the other is in control remains unclear, particularly in natural, diverse AMF communities, although recent evidence suggests that it is beneficial for a tree to maintain a diversity of fungal symbionts throughout its lifetime (Arguello et al . ).…”

Section: Discussionmentioning

confidence: 97%

Exploring the symbiont diversity of ancient western redcedars: arbuscular mycorrhizal fungi of long‐lived hosts

2017

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Arbuscular mycorrhizal fungi (AMF) are globally distributed, monophyletic root symbionts with ancient origins. Their contribution to carbon cycling and nutrient dynamics is ecologically important, given their obligate association with over 70% of vascular plant species. Current understanding of AMF species richness and community structure is based primarily on studies of grasses, herbs and agricultural crops, typically in disturbed environments. Few studies have considered AMF interactions with long-lived woody perennial species in undisturbed ecosystems. Here we examined AMF communities associated with roots and soils of young, mature and old western redcedar (Thuja plicata) at two sites in the old-growth temperate rainforests of British Columbia. Due to the unique biology of AMF, community richness and structure were assessed using a conservative, clade-based approach. We found 91 AMF OTUs across all samples, with significantly greater AMF richness in the southern site, but no differences in richness along the host chronosequence at either site. All host age classes harboured AMF communities that were overdispersed (more different to each other than expected by chance), with young tree communities most resembling old tree communities. A comparison with similar clade richness data obtained from the literature indicates that western redcedar AMF communities are as rich as those of grasses, tropical trees and palms. Our examination of undisturbed temperate old-growth rainforests suggests that priority effects, rather than succession, are an important aspect of AMF community assembly in this ecosystem.

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“…Because the commercial AMF mix that we used was purported to consist of four AMF species, the different effects of AMF availability on herbivore performance may be a function of differential colonization by AMF species under medium and high AMF availability. AMF species vary in their relative trading of nutrients (Lendenmann et al, 2011;Thonar et al, 2014;Argüello et al, 2016) and effects on plant phenotype (Gehring and Bennett, 2009;Bennett et al, 2013) which can alter herbivore performance (Roger et al, 2013;. However, cloning and sequencing of the AMF mix, and roots from milkweed plants grown under the same experimental conditions, with AMF-specific primers (Krüger et al, 2009) demonstrated that the AMF mix consisted only of F. mosseae (details in Supplementary Material).…”

Section: Discussionmentioning

confidence: 99%

Mycorrhizae Alter Toxin Sequestration and Performance of Two Specialist Herbivores

Meier

Hunter

2018

Front. Ecol. Evol.

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Multitrophic species interactions are shaped by both top-down and bottom-up factors. Belowground symbionts of plants, such as arbuscular mycorrhizal fungi (AMF), can alter the strength of these forces by altering plant phenotype. For example, AMF-mediated changes in foliar toxin and nutrient concentrations may influence herbivore growth and fecundity. In addition, many specialist herbivores sequester toxins from their host plants to resist natural enemies, and the extent of sequestration varies with host plant secondary chemistry. Therefore, by altering plant phenotype, AMF may affect both herbivore performance and their resistance to natural enemies. We examined how inoculation of plants with AMF influences toxin sequestration and performance of two specialist herbivores feeding upon four milkweed species (Asclepias incarnata, A. curassavica, A. latifolia, A. syriaca). We raised aphids (Aphis nerii) and caterpillars (Danaus plexippus) on plants for 6 days in a fully factorial manipulation of milkweed species and level of AMF inoculation (zero, medium, and high). We then assessed aphid and caterpillar sequestration of toxins (cardenolides) and performance, and measured defensive and nutritive traits of control plants. Aphids and caterpillars sequestered higher concentrations of cardenolides from plants inoculated with AMF across all milkweed species. Aphid per capita growth rates and aphid body mass varied non-linearly with increasing AMF inoculum availability; across all milkweed species, aphids had the lowest performance under medium levels of AMF availability and highest performance under high AMF availability. In contrast, caterpillar survival varied strongly with AMF availability in a plant species-specific manner, and caterpillar growth was unaffected by AMF. Inoculation with AMF increased foliar cardenolide concentrations consistently among milkweed species, but altered aboveground biomasses and foliar phosphorous concentrations in a plant species-specific fashion. Increased herbivore sequestration of cardenolides followed AMF-mediated increases in foliar cardenolide concentrations. Aphid performance declined with increasing foliar cardenolide concentrations, while caterpillar survival increased with aboveground biomass. Our findings suggest that by altering plant phenotype, the availability of AMF in soil has the potential to influence both top-down (via sequestration) and bottom up (via plant defense and nutrition) forces that operate on herbivores.

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Options of partners improve carbon for phosphorus trade in the arbuscular mycorrhizal mutualism

Cited by 68 publications

References 32 publications

Little evidence that farmers should consider abundance or diversity of arbuscular mycorrhizal fungi when managing crops

Little evidence that farmers should consider abundance or diversity of arbuscular mycorrhizal fungi when managing crops

Exploring the symbiont diversity of ancient western redcedars: arbuscular mycorrhizal fungi of long‐lived hosts

Mycorrhizae Alter Toxin Sequestration and Performance of Two Specialist Herbivores

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