Mycorrhizal Fungi in Nursery Production: Facts & Fiction - ARS : Home

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


• 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.


• 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.


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


STAGE III

• Test inoculum products on a small scale using non-inoculated plants for comparison.

• Verify whether inoculation causes an increase in mycorrhizal colonization.


• 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

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