Model Crop(s) and DifferentialsModel Crop(s) and Differentials

B.D. Gossen, K. Sharma, & M.R. McDonald BDG – AAFC Saskatoon; KS, MRM – University of Guelph

Clubroot Summit, March 7, 2012Support: CRMI

�� Research questionsResearch questions

�� Does response in other Does response in other species predict species predict response in canola?response in canola?

�� Would use of model Would use of model crops be more effective crops be more effective than studies on canola?than studies on canola?

�� Do we need a new Do we need a new differential set for differential set for Canada?Canada?

Research questions

� Does response in other species predict response in canola? - Short answer – Yes!

� Would model crops be more effective than studies on canola?- limited space, e.g., containment, growth cabinets- limited space, e.g., containment, growth cabinets- with pathotypes that don’t occur in the region

� Need for a differential set for Canada?- Reaction of existing differential sets to Canadian collections is not consistent (Howard, Strelkov).- Seed of several differential lines is very scarce, and as a result, more valuable than gold.

Arabidopsis thaliana

Advantages- Small size, short lifecycle- Small, sequenced genome- Lots of mutants available- Widely used as a model for canola in genetic studies for canola in genetic studies and susceptible to clubroot

Disadvantage- Growth habit VERY different from canola and other Brassica crop spp.

N.B. Assessment underway.

Wisconsin Fast Plants (RCBC)Brassica crop species selected for:- Small stature- Short generation time (~1 month)

AdvantagesAdvantages- Consistent seed availability (expensive!)- Used in many studies of Brassicae spp.Disadvantage- Clubroot reaction not known.

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2008 2009 2010

Reaction of Fast Plants to Pathotype 6

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B. carinataB. juncea

B. napus

B. oleraceaB. rapa

45H21

46A76

MeiChoi

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Clubroot Reaction of Fast Plants to P6 in Field (mean) vs. Growth Room Trials

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Field trial

Growthroom trialA

AA

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a

r = 0.91; P < 0.0001

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B. carinata B. juncea B. rapa var.communis

B. rapa B. oleracea B. napus

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A

B

C d

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Pathotype 3

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B. carinata B. rapa var. communis Iberis amara B. oleracea

Incidence

DSI

B. carinata B. rapa var. communis Iberis amara B. oleracea

Pathotype 6

0

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B. carinata B. juncea B. rapa var.communis

B. rapa var.utilis

Iberisamara

B. rapa B. oleracea B. napus

Pathotype 5

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100a

y y

w

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v

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b

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Pathotype 2

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B. carina B. junc Pak choy F-cabb Candytuft B. rapa B. olera B. napus

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z y

vw

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B. rapa subsp. Chinensis var. communis (Pak choy) *P6

B. napus * P6 B. carinata * P6

B. rapa * P6 Iberis amara * P6

Results

Field trials

• B. carinata and B. juncea were highly susceptible, several lines of B. rapa were moderately susceptible, and B. napus and R. sativus were resistant.

• The response was consistent over years.

Growth room trials

• Response to pathotype 6 under controlled conditions was strongly correlated with those from the field.

• A strong interaction in response to the pathotypes was observed for several of the lines.

Focus on differentials

• Problem with canola – MTAs required, weak, slow germination, rapid turnover of lines/cultivars

• Vegetable Brassicas – Slow turnover of cultivars, no MTAs, consistent response to pathotype 6 under controlled conditions, strongly correlated with results from field trials. from field trials.

• Shanghai pak choy has potential as universally susceptible check – rapid germination, commercial line with no MTA, international access

• RCBC have potential – differential reaction, consistent seed availability, no turnover

Focus on differentials (cont’d)

• Need to include representatives of the newest resistance sources, to test for development of new races

• The reaction of genotypes of a range of other Brassica crop spp. are being examined to Brassica crop spp. are being examined to determine if any might be useful in a new set of Canadian differentials. Need to co-ordinate this with breeders and industry

• Questions : How urgent is the need to new differentials? Should we characterize differentials based on single-spore isolates? How do we co-ordinate these studies?