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Mycorrhizal Fungi in Nursery Production:
Facts & Fiction
Mycorrhizal Fungi in Nursery Production:
Facts & Fiction
Carolyn ScagelUSDA-ARS-Horticultural Crops Research Laboratory
Corvallis, OR
What Are Mycorrhizae?• Partnership between
roots and fungi• Plant Fungi : Sugars
and other substances• Fungi Plant:
nutrients, water, hormones Carbohydrates
Water
Nutrients
Nut
rient
s
Wat
er
What Are Mycorrhizae?• Fiction:
All plants need mycorrhizae
• Facts:1. Almost all plants are capable of forming mycorrhizae.
2. Some plants do not naturally form mycorrhizae.
3. Plants can potentially grow & survive without the fungus.
4. The fungus is often completely dependent on the plant .
What Do Mycorrhizae Look Like?
• Several types of mycorrhizal associations:– Arbuscular mycorrhizae (AM)– Ectomycorrhizae– Ericoid mycorrhizae– Arbutoid mycorrhizae– Orchid mycorrhizae– Monotropoid– Ectendomycorrhizae
Arbuscular Mycorrhizae (AM)• Growth within root
cortical cells
• Vesicles, arbuscules
• External hyphae
• Most angiosperms, some gymnosperms (Taxus, Sequoia, Thuja, Chamaecypris), mosses, ferns
Ectomycorrhizae• Growth between root
cortex cells – Hartig Net
• Sheath on root surface
• External hyphae
• Betulaceae, Fagaceae, Pinaceae, Salicaceae, Myrtaceae
Ericoid Mycorrhizae• Growth within root
cortical cells
• Hyphal coils
• External hyphae
• Ericaceae, Emptetraceae, Epacridaceae.
Arbutoid Mycorrhizae• Growth within and
between root cells
• Sheath on root surface
• External hyphae
• Ericales genera including Arbutus, Pyrola, Arctostaphylos
Ecological Perspective
Read, 1984
Vegetation Heathland Conifer Forest Hardwood Forest Grassland
Nitrate
Ammonium
Organic
Form ofNitrogen
MycorrhizalType
Decreasing latitude or altitude
Ericoid
Ecto
Arbuscular
Grape Roots
Large Blueberry Roots
Small Blueberry Roots AMF Hyphae
1 cm = 10,000 µm
What Do Mycorrhizae Look Like?
• Fiction:You can tell a plant is mycorrhizal by looking at it.
• Facts:1. The only way to confirm whether a plant is colonized by
AM or ericoid fungi is by a microscope or DNA analysis.
2. Most ecto and arbutoid mycorrhizae can be seen on roots; however some do not produce a mantle that is visible without using microscope.
3. If inoculation effects plant growth do not assume the plant is mycorrhizal; other organisms or components of the inoculum may cause a plant response without colonization.
Why Are Mycorrhizae Important?•Nutrition
–Increase nutrient use efficiency–Decrease run off and leaching–Improved Water Quality
•Disease–Suppression of pathogens–Increase plant health–Decrease pesticide use
•Drought and Salinity–Increase efficiency of water use–Decrease crop loss–Increase acreage of farm land
•Soil Quality– Improve soil structure & stability–Decrease erosion & topsoil loss–Enhance nutrient retention
•Efficiency & Profitability– Improve root growth & survival–Decrease production time–Enhance marketability
•Product Quality–Alter phytochemical attributes– Increase flowering–Enhance nutritional value
Nutrient & Water UptakeRoot
Hyphae
• Hyphae extend out from roots into soil
• 50 to 100 times more reserves available to a mycorrhizal plant than a non-mycorrhizal plant
Root
Hyphae
Growth: Big Plant vs Little Plant
MYC
NM
MYCNM
Little plants may not be representative of normal production practices
Growth & Culture
None InoculatedHigh P
P-deficient leaf
None InoculatedLow P
Benefits sometimes are masked by cultural conditions
None Myc #1 Myc #2
Benefits sometimes are only seen belowground
Growth: Hidden
Fertilizer Uptake & Run-off
0
100
200
300
400
500
600
0 10 20 30 40 50 60 70 80 90Time After Planting (Days)
Con
duct
ivity
(mS)
. IN - NONE IN - MYC
OR - NONE OR - MYC
Response can depend fertility and type of fertilizerFrom Scagel, 2005
Drought & Salt Tolerance
Salt: Low High High LowNon-inoculated Inoculated
Inoculated Non-inoculated
Benefits sometimes only detectable plants are exposed to stress
Root Disease & Pests
Benefits may be indirectly due to other organisms enhanced in soil around the roots of a mycorrhizal plant
Soil Aggregation
Miller & Jastrow, 1992
Importance during in-field production and landscape however difficult to measure
Root Growth• Rate limiting step in
production of cuttings and tissue culture plants
• Correlated with plant survival after transplanting
• Implications to production efficiency and costs
InoculatedNon-inoculated
Benefit Depends on Goal
0
2
46
8
10
1214
16
18
0 20 40 60 80 100Percent Rooting (%)
Prim
ary
Roo
ts (#
)
NoneHormoneAMFHormone+AMF
From Scagel, 2001
Benefit Depends on Fungus
0
50
100
150
200
250
300
350
400
450
0 20 40 60 80 100Percent Rooting (%)
Roo
t Len
gth
(cm
)
None H OG H+OG
HE1 H+HE1 HE2 H+HE2
From Scagel, 2004
Benefit Changes with Time
0
50
100
150
200
250
1989 1990 1991
Roo
t Gro
wth
(g)
Control H M H+M
Spring Planting
1 year after planting
2 years after planting
From Scagel, 1999
Benefit Changes with Time & Goal
0
20
40
60
80
100
120
1989 1990 1991
Surv
ival
(%)
Control H M H+MFall Survival
From Scagel, 1999
Benefit change with culture and plant development
0
10
20
30
40
50
60
70
80
No SoilTreatment
SoilPasteurization
Stem
Em
erge
nce
(d)
.
No AMF AMF
0
20
40
60
80
100
120
2001 2002
Flow
er E
mer
genc
e (d
)
.
No AMF AMF
-15
-9
Zephyranthes spp. Brodiaea laxa+10
-12
From Scagel, 2004
Benefit Expressed as Quality
0123456789
10
2001 2002
Cor
ms
(#/p
lant
)
.
No AMF AMF
0
5
10
15
20
25
30
2001 2002
Flow
er (
#/pl
ant)
.
No AMF AMF
Sparaxis spp.
+1
+3 Sparaxis
+7
+9
From Scagel, 2004
Benefits?• If plants have mycorrhizae, benefits can vary
with:– the plant and fungal species in the association– the environmental and cultural factors present
during production or in the landscape.
• In many cases, the benefits of mycorrhizae are not recognizable unless:– non-mycorrhizal plants are used for comparisons– comparisons are made based on product quality
or performance of the product
Why Are Mycorrhizae Important?
• Fiction:Mycorrhizae will solve all my production problems
• Facts:1. Proof of benefit by research does not necessarily
translate in all production systems or landscape situations.
2. Benefits derived from mycorrhizae will depend on production goals or objectives.
3. Benefits may not be greater than costs. Evaluate the cost and benefit of using mycorrhizal fungi just like any other potential change in production practices.
Do I Need To Inoculate?
YesDo I have MYC?
No
Is MYC low?
No
Yes
Specific MYC?
No
Yes
Yes
Inoculate
Is your goal
MYC?
Yes
NoValue added
benefit?
Do I Have Mycorrhizae?
Bog Age (Years)0 5 10 15 20 25 30 35 40
Myc
orrh
izal
Col
oniz
atio
n(%
of r
oots
with
myc
orrh
izal
str
uctu
res)
0
20
40
60
80
100
120
Scagel 2002
Inoculation Trials
0
5
10
15
20
25
30
35
40
45
3/15/00 7/28/01 12/10/02 4/23/04
Roo
t Col
oniz
atio
n (%
)
Non-inoculatedInoculated
Bog 4 - Youngest Bog
0
5
10
15
20
25
30
35
40
45
3/15/00 7/28/01 12/10/02 4/23/04
Roo
t Col
oniz
atio
n (%
)
Non-inoculatedInoculated
Bog 1 - Oldest Bog
Inoculation response dependant on age.Inoculation can increase colonization…but levels are still not
very high
Scagel 2003
Is Colonization Low?
0
20
40
60
80
100
120
140
MAR MAY SEP OCT NOV
Col
oniz
atio
n In
tens
ity (%
Roo
ts)
Control
Inoculated
'MISTY'
0
20
40
60
80
100
120
140
MAR MAY SEP OCT NOV
Col
oniz
atio
n Fr
eque
ncy
(% P
lant
s)
Control
Inoculated
'MISTY'
Natural colonization can occur but natural fungi may not be retained
From Scagel, Wagner, Winiarski, 2005
I Want Specific Fungi
0
5
10
15
20
25
MAR MAY SEP OCT NOV
Col
oniz
atio
n In
tens
ity (%
Roo
ts) Control
Inoculated
'RUBEL'
0
5
10
15
20
25
MAR MAY SEP OCT NOV
Col
oniz
atio
n In
tens
ity (%
Roo
ts) Control
Inoculated'BLUECROP'
Colonization can change with time and cultivar –Host/fungus specificity?
From Scagel, Wagner, Winiarski, 2005
Cultivar x Fungus Interaction
0
5
10
15
20
25
30
Bluecrop Blueray Darrow Earliblue GeorgiaGem
Patriot Spartan
Roo
t Col
oniz
atio
n (%
)
.
NoneO. griseumH. ericaeP. ericae
Certain cultivars more responsive to specific fungi.
Scagel, 2005
Cultivar x Fungus Interaction
0
20
40
60
80
100
120
BC (>3gen) EB (>2gen) PA (>2gen) GG (>1gen)
Leaf
Bio
mas
s (g
)
Non-Inoculated Inoculated
~27%
~36%
~92%
Breeding selection processes may decrease responsiveness to fungi
From Scagel, 2005
Culture x Fungus Interaction
0
5
10
15
20
25
30
35
None O. griseum H. ericae P. ericaeInoculation Treatment
Roo
t Col
oniz
atio
n (%
)
.
InorganicOrganicCertain fungi more sensitive to fertilizer type.
Scagel, 2005
Inoculation?
To become mycorrhizal plants require:
•Viable inoculum available to roots
•Inoculum compatible with host type
•Environmental and cultural conditions suitable for colonization
Do I Need To Inoculate?• Fiction:
Plants are mycorrhizal if they have been inoculated and are ‘naturally’ mycorrhizal if they have been grown in soil.
• Facts:1. Application of inoculum or growing plants in soil does not
guarantee mycorrhizae formation.
2. If mycorrhizae formation is a production goal, then process and quality control measures need to be in place to evaluate the success of practices used to achieve colonization.
When Do I Manipulate Mycorrhizae?
‘Applied’ Mycorrhizal Fungi Inoculum
Hormones
CuttingRooted Cutting,
TC Plantlet, Seedling
FinishedPlant
Environment and Culture (light, heat, nutrients, moisture, soil, media, fungicides, pesticides, etc.)
‘Natural’ Mycorrhizal Colonization
Established Plant
Propagator Retailer ConsumerGrower
When Do I Manipulate Mycorrhizae?
• There are several opportunities during different stages of production. Timing depends on goal and culture.
• Benefits of having mycorrhizae are cumulative and may not be visible during production.
• Early mycorrhizae formation improves ability to capture benefits of the association.
When Do I Manipulate Mycorrhizae?
• Fiction:Once plants have mycorrhizae they retain them and the benefits from mycorrhizae that occur in the nursery will occur in the landscape
• Facts:1. Changes in the environment and culture that occur
during different stages of production can alter mycorrhizal status of the plant.
2. Mycorrhizal fungi that perform well during early states of production may not be the best fungi during later stages of production or in the landscape.
How Do I Use Mycorrhizal Fungi?
STAGE I
• Determine the specific goals or objectives for using mycorrhizal fungi in your production system
• Evaluate current mycorrhizal status of crop under current production conditions
• Work with commercial suppliers, extension personnel, or other people familiar with mycorrhizal fungi to determine whether cultural manipulation can improve mycorrhizal status or whether inoculation is needed.
How Do I Use Mycorrhizal Fungi?
STAGE II
• If inoculation is needed, assess different products and determine host plant/fungus types required.
• Aspects of inoculum products include:– Purpose of product and how to use it– Content with species names, etc.– Guarantee of pathogen free content– Mycorrhizal effectiveness in a standard test– Maximum dilution of content– How to store inoculum– Recommended date of use
How Do I Use Mycorrhizal Fungi?
STAGE III
• Test inoculum products on a small scale using non-inoculated plants for comparison.
• Verify whether inoculation causes an increase in mycorrhizal colonization.
How Do I Use Mycorrhizal Fungi?
• Fiction:Inoculation with mycorrhizal fungi does not effect plants
• Facts:1. Inoculation does not guarantee colonization. If you
inoculate always verify colonization success.
2. If inoculation results in colonization, plants are influenced by the association; however – the effect may not meet specific goals of inoculation; or– other production practices may mask potential benefit
If your goal is to produce a mycorrhizal plant, then learning how to grow the fungus is as important and
knowing how to grow the plantMYCORRHIZAE = FUNGUS + ROOT