Managing sclerotinia stem rot in canola Canola Research Summit Winnipeg, MB April 12-13, 2011 H.R. Kutcher, F. Dokken-Bouchard, T.K. Turkington, W.G.D. Fernando, P. Bullock, D.L. McLaren, S. Boyetchko, L. Buchwaldt, D. Hegedus and I. Parkin
Sclerotinia stem rot strategies • Foliar fungicides are a very important strategy for sclerotinia stem rot control • Decision support systems – often including climatic components • Rotation • Fertility/ Lodging • Field scouting & record keeping • Tolerance/ resistance
Sclerotinia stem rot of canola
Melfort, 1998 60 50 40 31% 33%
30 20 10 0 Sclerotinia incidence (%)
Yield (bu/ac)
Unsprayed Ronilan Benlate
Melfort, 1999 35 30 25 Unsprayed Ronilan Benlate
20 15 10 5 0 Sclerotinia incidence (%)
Yield (bu/ac)
Seeding date study, Melfort ~1999
Seeding rate LSD = NS
% stem rot incidence
22
21
20
20
20 18 18 16 14 12 2.8
5.1
7.3
Seeding Rate (Kg/ha) A98013
Seeding date study, Melfort ~1999
9.5
Sclerotinia incidence (%)
Effect of rotation on sclerotinia incidence 10 8 6 4 2 0 1
2
3
4
5
Years Years since previous canola crop Years since previous sclerotinia-susceptible crop From Report on 1997 Western Canada Canola Disease Survey, R.A.A. Morrall et al.
Effect of rotation on sclerotinia incidence 35
D is e a s e In c i d e n c e (% )
30 25 20 sclerotinia
15
blackleg 10 5 0 1
2
3
4
Frequency of canola in rotation (yrs)
5
From Report on 1997 Western Canada Canola Disease Survey, R.A.A. Morrall et al.
McLaren
Turkington Kutcher
Sclerotinia incidence (%)
Effect of nitrogen fertilizer on sclerotinia incidence in western Canada 25 20 15 10 5 0 0-20
21-40
41-60
61-80
81-100
>100
Nitrogen (lbs/acre) Argentine
Polish
From Report on 1997 Western Canada Canola Disease Survey, R.A.A. Morrall et al.
Fertility rate and % sclerotinia stem rot incidence % stem rot incidence
30
Sig. linear increase
27
25 19
20 15
13
10 5 50%
A98013
100%
150%
Fertilizer Rate
From Report on 1997 Western Canada Canola Disease Survey, R.A.A. Morrall et al.
Scouting • Pathogen identification: what is out there and how will it be influenced by crop management, crop development and weather? Pre-spray scouting (to determine benefit of fungicide)
• Past experience: what diseases occur regularly and particularly last year Swathing time scouting (to collect information for future decisions)
Bloom staging guides
Fungicides available for sclerotinia stem rot control in canola Group 2 – risk of developing resistance: medium to high Rovral Flo iprodione Group 3 – risk of developing resistance: medium Proline 480 SC prothioconazole Group 7 – risk of developing resistance: medium Lance boscalid Group 11 – risk of developing resistance: high Quadris azoxystrobin Groups 9 &12 – risk of developing resistance: medium & low - medium Astound Cyprodinil & fludioxonil Unclassified – bio-fungicide Contans WG Coniothyrium minitans Serenade Max/ASO Bacillus subtilis
Improved assessment of canola petal infestation • Graduate student (M.Sc. – U of A) Drs. T.K. Turkington, S. Strelkov, H.R. Kutcher, B.D. Gossen, D.L. McLaren, F. Dokken-Bouchard, K. Rashid and V. Bisht • Develop a qPCR detection method for S. sclerotiorum present on infested petals/flowers • Determine the relationship between the quantity of S. sclerotiorum DNA, agar plate petal infestation assessments, and stem rot incidence/severity • Correlate qPCR detection, agar plate assessements and weather-based forecasts with final disease incidence/severity • Successful deployment of qPCR in private seed testing labs for commercial use
Weather Based Assessment of Sclerotinia Stem Rot Risk in Canola • MSc student, Ms Reanne Pernerowski Drs. Paul Bullock and Dilantha Fernando • Develop a means of predicting sclerotinia stem rot based on weather conditions, allowing more accurate fungicide application timing • Use standard weather conditions to accurately model sclerotinia incidence/ severity among varying crop densities through the use of a microclimate model • Compare disease incidence under standard weather conditions vs. conditions of continual moisture supply (misting) • Monitor the dispersal of spores within a canola field containing various crop densities and from a neighboring wheat field
Bacterial antagonists against Sclerotinia sclerotiorum on canola • 10 bacterial strains suppress: – Mycelial growth, ascospore germination/viability & sclerotial formation • Broad spectrum activity – (Rhizoctonia solani, Phoma lingam, Alternaria brassicae, Phytophthora infestans)
Incorporation of bacterial metabolites into agar
S. Boyetchko – AAFC, Saskatoon
Dr. Fernando’s Biological Control Program • Identification of key genes in biocontrol (mainly genes controlling antibiotic production) from Pseudomonas chlororaphis strain PA23 against Sclerotinia. • Novel regulatory gene identified in biocontrol from strain PA23 (patented). • In-vivo gene expression of bacterial biocontrol genes under different environmental conditions to enhance biocontrol activity of Pseudomonas chlororaphis strain PA23. PA-23
Sclerotinia Sclerotinia
Phenazine (one of the Antibiotics defused in to medium)
Pseudomonas chlororaphis PA-23
Research to utilize sclerotinia resistance in newly identified B. napus germplasm for cultivar improvement Lone Buchwaldt, Dwayne Hegedus and Isobel Parkin AAFC, Saskatoon Research Centre
A break through in sclerotinia resistance screening has enabled identification of new resistant germplasm, development of molecular markers and identification of B. napus defense genes
1. Screening resembles natural infection of stems
2. Agar plugs with mycelium are attached to the stem with Parafilm
3. Lesion growth is measured over three weeks
4. Example of a resistant and a susceptible line
New B. napus lines were identified with high level of sclerotinia resistance. Figure 1 shows lines sorted from resistant to susceptible in six geographical regions. 125
125 AUDPC
Figure 1.
% soft + collapsed lesions 100
75
75
Zhongyou 821 50
50
25
25
% soft + collapsed lesions
AUDPC
100
PAK54 PAK93 0
0
China
E-Europe W-Europe
Pakistan
Japan
South Korea
Zhongyou 821 from China was the first resistant B. napus we used for development of molecular markers linked to resistance (in collaboration with four canola breeding companies). PAK54 and PAK93 from Pakistan are currently being utilized for marker development (SaskCanola - DIAP) Additional funding is needed to exploit resistance sources from Japan and South Korea.
Results obtained with Zhongyou 821 Molecular markers (A1a - C9b) linked to nine QTLs for sclerotinia resistance were identified (Fig.2). Three QTLs contributed 30 - 40% to resistance and are suitable for marker-assisted-selection in canola breeding. Defense genes up-regulated in during sclerotinia infection have been identified (Fig. 3). Lectin and O-methyl transferase were tentatively mapped to resistance QTLs (Fig. 2). Development of gene specific markers for O-methyl transferase and other genes is in progress. Selected defense genes have been cloned and B. napus transformation is in progress. Fig. 2 A1
A2
A3
A4
A5
A6
A7 A6a
A1a
A8
A9
A10
Fig. 3. Defense genes up-regulated in Zhongyou 821 140
A7a
O-mt trans A6b
A1b
120
A7b
BN24464
Lectins
BN25790 BN15489
A3a
A7c
Lectin
A7d
A1d
C1
C2
C3
BN18917 BN20514
A3b
Lectin
F o ld e x p re s s io n
A1c
100
C4
C5
C6
C7
C8
C9
BN18865 BN26461
80
BN23610 BN13257 BN24404 BN20039
60
BN18437 BN14638
O-methyl transferase
40
BN26419 BN23990 BN22522 BN25570
C3a
Lectin C3b
C6a
O-mt trans C6b
regions with complete or partial homology
BN14979
20
BN26461
C9a
BN11472
C9b
BN22148 0 6hpi
12hpi
24hpi
48hpi
72hpi
Hours after inoculation
A unique opportunity exists to make progress in the breeding of canola cultivars with sclerotinia resistance. Additional funding will be used for development of molecular markers linked to resistance in lines from Japan and South Korea, and for identification of specific defense genes as we are currently doing in Zhongyou 821.
Summary • Sclerotinia stem rot of canola is extremely variable in occurrence and severity from year-to-year, region-to-region and field-tofield. • Foliar fungicides remain the main control strategy. Tools that provide guidance to growers for fungicide application exist, and research to refine these tools continues. • Resistant/ tolerant varieties are available and efforts continue to improve varietal resistance, in both the public and private sectors.
