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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.
60
80
100
Dis
ease
sev
erity
inde
x
2008 2009 2010
Reaction of Fast Plants to Pathotype 6
0
20
40
B. carinataB. juncea
B. napus
B. oleraceaB. rapa
45H21
46A76
MeiChoi
Dis
ease
sev
erity
inde
x
Clubroot Reaction of Fast Plants to P6 in Field (mean) vs. Growth Room Trials
80
100
Dis
ease
sev
erity
inde
x
Field trial
Growthroom trialA
AA
Aa
a
b
a
r = 0.91; P < 0.0001
0
20
40
60
80
B. carinata B. juncea B. rapa var.communis
B. rapa B. oleracea B. napus
Dis
ease
sev
erity
inde
x
A
B
C d
c
b
Pathotype 3
0
25
50
75
100
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
25
50
75
100
B. carinata B. juncea B. rapa var.communis
B. rapa var.utilis
Iberisamara
B. rapa B. oleracea B. napus
Pathotype 5
0
25
50
75
100a
y y
w
x
v
c
b
c
a
az
ww
c
d
Pathotype 2
0
25
50
75
100
B. carina B. junc Pak choy F-cabb Candytuft B. rapa B. olera B. napus
b
z y
vw
x
w
c
de
aa
dvw
v ve
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?