Alliaria Petiolata and Mycorrhiza

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Introduction

Electron micrograph of the Ebola Zaire virus. This was the first photo ever taken of the virus, on 10/13/1976. By Dr. F.A. Murphy, now at U.C. Davis, then at the CDC.

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There is strong evidence that plant–soil community feedback play a major role in plant species coexistence [1]. Soil microbial communities have been shown to rapidly change in response to plant identity [2;3;4]. These microbial community compositions can have strong direct effects on the outcome of plant–plant interactions [5,6]. The invasive plant, Alliaria petiolata (Bieb.) Cavara & Grande, has been shown to effect microbial communities and thus effect plant to plant interactions.

Invasive Plants

Invasive species can and do effect soil microbial communities. These interactions in areas of low diversity can be classified as competitive dominance, inhibition and positive feedback [1]. Monotypical stands formed by invasive species sometimes have symbiotic relationships novel to the invaded areas. These novel mutualisms could increase the competitiveness and niche-space of invasive species [7], a form of the ‘empty niche’ hypothesis [8]. The ‘degraded mutualist hypothesis’ proposes that some invasive plants will inhibit native symbiotic communities, indirectly reducing native plant fitness [9; 10].

Microbial Species

At least 80% of the world's plants form mycorrhizal assocations [32]. Arbuscular mycorrhizal fungi (AMF), phylum Glomermycota, and ectomycorrhizal fungi (EMF), phylums Basidiomycota, Ascomycota, Zygomycota are soil mutualists with resident plant roots acting as an extension of the root system. Mycorrhizal associations lead to protection of the plant from soil pathogens [33] and an enhanced tolerance to drought [34].

Allelopathy

Allelopathy is the suppression of germination or growth of neighboring plants by the release of toxic secondary chemical compounds. These secondary metabolites are leached, exuded or volatilized into the environment from the plant [11] and may act as act as novel weapons to suppress mycorrhizal fungi [12; 13; 14; 15], inhibit germination [16;17; 18; 19] and decrease survival of native mycorrhizal plants [13].

Alliaria petiolata

For at least two decades, garlic mustard (Alliaria petiolata (Bieb.) Cavara & Grande) a European biennial herb, has been a serious invader of natural areas and woodland communities of North America [20; 21]. Garlic mustard seeds germinate in early spring, and remain as an evergreen basal rosette during the first year; densities of up to up to 5,080 seedlings per square meter have been recorded [22; 23) During the second year, rosettes bolt between mid-April and mid-May and may occur in densities as high as 303 plants per square meter [22]. The flowers begin anthesis in early spring, set seed in June, and senesce by mid-late July [22; 23). Seeds germinate after a period of at least 14 weeks of cold stratification at temperatures from 1 degree Celsius (°C) to 10°C [24]. In the first spring following production, 70% of seeds germinate but may remain viable for up to 10 years [24; 25].

Alliaria petiolata Allelopathy

Alliaria petiolata has been shown to inhibit plant growth and mycorrizal fungi. This effect is most likely due to secondary metabolities exudated by this plant. Glucosinolates, alliarinosides, flavoinoid glycosides and cyanide all have been shown to be part of the suite of chemicals produced by this plant, with glucosinolates being more present in belowground tissues [17; 26; 27]. Interestingly, compounds from glucosinolates predominately degrade to the secondary metabolites, allyl isothiocyanate and benzl isothiocyanate, both shown to be inhibitory to fungi [28].

Effects on Mycorrizha

There is growing interest in invasion ecology as to the effect of invasive plants species on mycorrhizae in soil and how these invasive plants can affect native plants and diversity of mycorrhiza [29]. Native tree species Acer saccharum, Acer rubra and Fraxinus americana all showed less colonization of roots by AMF in soil and slower growth in soil with a history of Alliaria petiolata suggesting the methods of suppresses is microbially-mediated [10]. Extracts inhibited the growth of EMF and led to changes in EMF communities in invaded soils, with strongest inhibition within 10 cm of patches [14]. Other studies have shown while no effect was seen on total root length colonization on herbaceous plants with Alliaria petiolata presence, there was some effect of Alliaria presence on mycorrizal community structure with the plant Maianthemum racemosum (29). Understanding if and how the mycorrhizal association influences plant invasion may be a key aspect of the ecology and management of invasive plant species, as well as the conservation biology of native habitats [30]. Further study of volatiles released by garlic and their effect on mycorrhizal associations is needed [17].

Niche

Describe the physical, chemical, or spatial characteristics of the niche where we might find this interaction, using as many sections/subsections as you require. Look at other topics available in MicrobeWiki. Create links where relevant.

Microbial processes

What microbial processes are important for this microbial interaction? Does this microbial interaction have some ecosystem-level effects? Does this interaction affect the environment in any way? Describe critical microbial processes or activities that are important in this interaction, adding sections/subsections as needed. Look at other topics in MicrobeWiki. Are some of these processes already described? Create links where relevant.

Key Microorganisms

What specific kinds of microbes are typically involved in this interaction? Or associated with important processes? Describe key groups (genera, species) of microbes that we find in this environment, and any special adaptations they may have evolved to survive in this environment. List examples of specific microbes that represent key groups or are associated with important processes found in this environment. Add sections/subsections as needed. Look at other microbe listings in MicrobeWiki. Are some of the groups of microbes from your environment already described? Create links to other MicrobeWiki pages where possible.

Current Research

Enter summaries of recent research here--at least three required

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by <your name>, a student of Angela Kent at the University of Illinois at Urbana-Champaign.