HAL presentation template

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DNA assays to manage risk of soilborne disease
in potatoes
Alan McKay, Robin Harding, Nigel Crump, Tonya
Wiechel, Kathy Ophel Keller
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Objective
Reduce losses from soilborne diseases
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Most decisions to reduce risk of soilborne
diseases have to be made before planting
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Detecting pathogens before planting

• DNA assays can detect a wide range of pathogens
• SARDI uses this technology to deliver
• Research tools
• PreDicta B to grain growers
• APRP project is developing similar service for
  potato growers

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PreDicta B testing service

• Cereals
• Cereal cyst nematode
• Take-all
• Rhizoctonia solani AG8
• Crown rot
• Pratylenchus neglectus
• Pratylenchus thornei
• Peas
• Blackspot of peas

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Potato pathogen targets

• Potatoes
• Black dot
• Powdery scab
• Rhizoctonia solani AG2.1
• Rhizoctonia solani AG2.2
• Rhizoctonia solani AG3
• Common scab
• Meloidogyne fallax
• Others

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Basis

• DNA assays quantifies pathogen levels in soil not
  disease.

Pathogen
Disease
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Powdery scab spore balls (Spongospora
subterranea) added to soil and DNA levels
detected.


Rob Harding, SARDI
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Pre-sowing soil DNA levels (Colletotrichum
coccodes) and harvest tuber black dot incidence.
eastern SA, 2007-09
Black dot incidence ()
pg DNA C. coccodes DNA/g soil
Robin Harding, 2009
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Take-all and soil Ggt
NZ Wheat crops 2003
Bithell, McKay Cromey
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paddocks with TAIgt30
Bithell, McKay Cromey
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Sampling
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Powdery Scab pathogen DNA
EM38 Map
DNA level
Rob Harding, SARDI
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Sampling-Management Units
Approx 0.5ha
Approx 0.1ha
Approx 1.5ha
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Whats required for a testing service

• Risk categories for the tests Below detection,
  Low, Medium, High
• Sampling strategy
• Management options for each risk category
• Summarise role of environment on disease risk
• Manual training course consultants / growers.

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New project objectives (anticipated)

• Develop Manual - International links
• Work with grower groups

• Shortlist tests
• Black dot
• Powdery scab
• Rhizoctonia solani AG2.1
• Rhizoctonia solani AG2.2
• Rhizoctonia solani AG3
• Common scab
• Meloidogyne fallax
• Others

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APRP DNA Probes Team

• SARDI
• Kathy Ophel Keller
• Robin Harding
• Trevor Wicks
• Barbara Hall
• Herdina
• Alan McKay
• CSIRO
• Diana Hartley

• DPI VIC
• Tonya Wiechel
• Nigel Crump
• NZPFR
• Richard Falloon
• Farhat Shah
• PPIAC
• Paul Frost
• Dave Antrobus
• SA Potato Growers (Black Dot)

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Field pre-plant Spongospora soil DNA level and
powdery scab incidence SA/Vic 2007-08
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Pot bioassay Rhizoctonia AG3 DNA levels and
incidence of Black Scurf on daughter tubers
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Putative Pre-plant DNA Thresholds

• Powdery scab (800-1000 pg/g soil)
• Common scab (200 pg/g soil)
• Rhizoctonia
• AG 2-1 (1000 pg/g soil)
• AG-3 (100 pg/g soil)

Based on bioassay results and limited field
observation