West Coast Nut September 2019

MYCORRHIZAL FUNGI
HAVE BENEFITS IN AGRICULTURE
Mycorrhizal fungi and plants have a mutually
beneficial relationship.
By CECILIA PARSONS | Associate Editor
Cover crop in alley. Photo courtesy of Cecilia Parsons.
RESEARCHERS WHO ARE EXPLORING THIS
relationship are finding that mycorrhizal fungi are a vital
part of ecosystem health around the world—not only in
less intensively managed ecosystems but in agricultural landscapes
as well.
Mycorrhizal Fungi
Mycorrhizal fungi colonize the root system of a host plant to
form a symbiotic relationship and assist with water and nutrient
acquisition. In return, the plant provides the fungus with energy
in the form of carbohydrates, or sugars. In addition, these
microscopic fungi may also play an important role in minimizing
the impacts of stress and disease on plant hosts.
Mycorrhizae exist as microscopic threads called hyphae and,
when bunched together in a mass, form a net-like structure
called mycelium that continues to grow and explore the soil. The
mycelium of a single mycorrhizae can extend out to connect
multiple plants or connect with other mycorrhizae to form a
huge underground web called a common mycorrhizal network.
As these networks extend throughout the soil, they start to play
a role in supporting important agricultural services related to
soil structural maintenance, water dynamics, nutrient cycling,
and disease suppression.
Fungal Hyphae
Plant roots can gain access to soil water and nutrients via
associations with mycorrhizal fungi through direct links
between root and fungal cells. Roots need to be in direct
contact with soil to access water and nutrients and, in some
cases, can be restricted because of compacted soil conditions.
Fungal hyphae, which are much smaller than plant roots, can
improve access to soil nutrients and water for plants by exploring
more extensively throughout the soil profile and obtaining
nutrients and water from smaller soil aggregates. In fact, plants
with mycorrhizal colonization have 50-100 times more nutrient
reserves available than a non-colonized plant. Fungi also
decompose more complex organic compounds that are then
made available in simpler forms to other soil organisms, such
as microbes, that perform additional services. Mycorrhizal
fungi thus play an invaluable role in supporting plant health
and growth, both of which are essential to agricultural
productivity.
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Impacts to Soil Health
Although mycorrhizal fungi play an important role in both
maintaining soil structure and improving plant health and
growth, agricultural activities—including tillage, nutrient
applications, fumigants, and anaerobic soil conditions—can
significantly impact overall soil health and the fungal communities
that rely on good soil conditions. This ultimately impacts
the fungal community’s ability to provide the services with
which crops rely on. Given that most crops can form associations
with mycorrhizal fungi and that there are many benefits
of interest for agricultural productions, it is imperative that we
better understand how to create soil environments that support
fungal communities and services.
As the importance of microbial communities, including
fungi, have become an increasingly popular topic in agriculture,
focus has turned to how management of our soils and crops
impacts the soil ecosystem and, subsequently, the capacity
for the soil to provide ecological and production benefits.
University of California, Davis, plant sciences researchers
Continued on Page 22
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West Coast Nut September 2019