The Role of ‘Clean’ Plants in Disease Management

S.J. Harper, WSU

There are over 70 grapevine infecting viruses and virus-like agents currently known.

• Some are specific to grapevines, many have a wide host range.

• New viruses are being reported every year.

CPCNW

Grapevines are ‘dirty’ plants

• Grapevine leaf roll - GLRaV-3 CPCNW

Grapevines are ‘dirty’ plants

• Red blotch - GRBaV CPCNW

Grapevines are ‘dirty’ plants

Grapevines are ‘dirty’ plants

• Pierce’s Disease - Xylella fastidiosa CPCNW

Grapevines are ‘dirty’ plants

Infection by virus-lie agents cause:

• Delayed ripening

• Smaller fruit size

• Changes in sugar content

• Yield losses

In short, infection reduces profit.

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Grapevines are ‘dirty’ plants

Control measures for virus-like pathogens are limited.

• Spray for vectors

• Remove infected plants

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Grapevines are ‘dirty’ plants

Pathogen control is expensive:

• Xylella fastidiosa control is estimated to cost California $104.3 million per year

• Up here in Washington, GLRaV-3 removal and replanting is estimated to cost $7754 per acre.

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Grapevines are ‘dirty’ plants

Where are the viruses coming from?

• Everywhere.

• No region has all 70+ pathogens present.

• But no region is 100% free of viruses either.

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Where are the viruses coming from?

Insect vectors can spread a pathogen within a vineyard or region.

• But the bugs have to get the virus from somewhere.

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Where are the viruses coming from?

People are far more efficient vectors of viruses than bugs.

• Movement of planting material between countries, states, nurseries, and growers.

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Where are the viruses coming from?

Propagating infected material is the #1 reason these pathogens persist.

• Self-propagation

• Propagation from ‘neighbors’

• ‘Suitcase’ imports

• Source of inoculum for bugs to spread.

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Where are the viruses coming from?

Effective pathogen control

= Breaking the cycle of

propagating infected material

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What are clean plants? CPCNW

‘Clean’ plants are propagative material that has:

• Been tested (repeatedly) for pathogens.

• Found to be free of economically important diseases.

What are clean plants? CPCNW

Testing by itself means very little.

• ‘Clean’ or ‘certified’ plants are the product of a process, or a chain-of-custody.

• This starts with the clean plant centers around the country, then nurseries.

The National Clean Plant Network CPCNW

The National Clean Plant Network CPCNW

The grapevine NCPN centers:

• UC Davis

• WSU Prosser

• Missouri State

• Cornell Univ.

• Florida A&M

CPCNW @ WSU Prosser

• The Clean Plant Center Northwest (CPCNW) is based at the WSU Irrigated Agriculture Research and Extension Center (IAREC) in Prosser, WA

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The clean plant process CPCNW

Introduction Domestic or International

Initial Virus Testing Is it infected? With what?

Cleanup Meristem Culture Thermotherapy

Secondary Testing Is it still infected?

Propagation Mother plants are stored at CPCs

Final Testing Virus free?

Released to the public

The clean plant process

Diagnostics:

• PCR testing

• HTS (NGS)

• Biological Indexing

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The clean plant process

• Meristem tissue culture CPCNW

The clean plant process

• Propagation in screen houses and foundation blocks.

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The clean plant process

• Budwood

• Green cuttings

• Mist propagated plants (MPPs)

• Tissue culture vials

• Plugs

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The clean plant process

Material moves from clean plant centers to nurseries.

• This is where the certification process starts

• Certification provides a standard for cleanliness.

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Certification is a process CPCNW

Washington certification standards: • Grapevine fanleaf virus • Grapevine leafroll-associated viruses • Grapevine virus A • Grapevine virus B • Grapevine rupestris stem pitting virus • Arabis mosaic virus • Tomato ringspot virus • Grapevine red blotch virus • Grapevine vein clearing virus • Xylella fastidiosa • Daktulosphaira vitifoliae (Grape phylloxera) • Planococcus ficus (Vine Mealybug).

Certification is a process CPCNW

• Levels of certified plants

G1

G2

G3

G4

Mother plant

Foundation

Registered Block

Certified

Clean Plant Centers

Nurseries

Certification is a process CPCNW

• General requirements for certification:

• Certified stock must be inspected and tested

• Nursery maintains records identifying the G1 sources of registered plants

• The nursery is responsible for trueness to type

Certification is a process CPCNW

• Nurseries must:

• Obtain material from a clean plant center

• Be able to trace each generation back to the original G1 plant

• Cooperate with state agencies for regular testing of G2/G3 blocks

Certification is a process CPCNW

• Once the plant, usually G3 or G4, reaches the end user, a grower, the plant is no longer certified

Where can I get certified plants? CPCNW

Washington

• Cloud Mountain Farm Center

• Inland Desert Inc.

• Sidhu & Sons dba Briggs Nursery, LLC.

• Ste. Michelle Wine Estates LTD.

• Terroir Nouveaux Nurseries, LLC.

Where can I get certified plants? CPCNW

Oregon

• Apical Vines Nursery • Bailey Nurseries • Brigadoon Vineyards • Cole Family Vineyards • Countryside Nursery • Cutting Edge Grapevines • Ethell Development Co. • King Estate Vineyards • Kraemer’s Nursery Inc.

• Melrose Vineyards • Meyer Nursery & Orchard • Northwoods Nursery • Plaisance Viticulture • St. Joseph Orchard • Sunset Knoll Vineyard • Weeks Berry Nursery

Myths about clean plants CPCNW

“All clean plants are the same”

• Just because material is ‘certified’ by the state of origin, doesn’t mean it will be accepted by your state’s nursery certification scheme.

• Standards differ greatly.

Myths about clean plants CPCNW

“The nursery was certified, so the plants are clean”

• Nurseries can maintain and sell both certified and normal plants.

• Confirm what you’re buying.

Myths about clean plants CPCNW

“If I plant clean plants, they’ll stay clean”

• Preventing reinfection is up to the grower.

• Have a comprehensive disease management strategy.

Integrated disease management CPCNW

Certified plant material:

• Reduces the spread of viruses and other systemic pathogens.

• Is part of an integrated management scheme.

Integrated disease management CPCNW

What else do you need to do?

• Screen vineyards regularly for virus-like diseases.

• Spray for vectors.

• Remove infected plants.

Integrated disease management CPCNW

This is a community effort to reduce disease pressure.

• Don’t mix certified and non-certified material.

• Encourage your neighbors to use clean planting stock.

Integrated disease management CPCNW

Clean Plants

Vector Control

Testing & Eradication