1. Sudden Death Syndrome of Soybean
Dr. Jason Bond, Plant Pathologist
Southern Illinois University

2. Sudden Death Syndrome Disease and Impact Pathogen Biology
Cultural Management
Host Resistance

3. Yield Losses – Northern US
Disease
3-year average
(bu in millions)
Soybean cyst nematode
122.4
Phytophthora rot
42.1
Seedling diseases
41.1
Sudden death syndrome
22.7
Charcoal rot
17.6
Brown spot
16.2
Brown stem rot
14.1
Anthracnose
11.3
Sclerotinia stem rot
10.0
Frogeye leaf spot
7.6
Fusarium root rot
Source: Allan Wrather, UM, Portageville, MO

4. Fusarium virguliforme (= F. solani f. sp. glycines)
Soilborne, root rotting fungus that colonizes tap root and crown
Produces a toxin(s)
Foliar symptoms generally start at R2 in field

5. Symptoms

6. Similar Foliar Symptoms
Stem Canker Phytophthora stem rot

7. Similar Foliar Symptoms
Brown Stem Rot
SDS

8. Spread of SDS
1993
2002
1997
2005?
2000
1993
1999
2004
1997
1986
2000
1984
1992
1986
1984
1997
1986
1971
1984
1984
1997
1997
1986

9. Rating Foliar Symptoms
Disease Incidence (DI) - % of plants in the plot showing leaf symptoms.
Disease Severity (DS) - Severity of diseased plants scored on a 1-9 scale.
Disease Index (DX) = (DI*DS)/9

10. DX

11. DX

12. DX

13. Impact on Yield
SDS is correlated to the yield potential provided by the environment
Popular misconception that SDS does not cause yield loss
Yield loss occurs when infection occurs early in a high yielding environment (adequate rainfall), and symptoms are expressed at or near flowering.

14. Impact on Yield

15. Environment SDS severity is increased with: Early planted fields
Compacted soil
High moisture, low soil temperature during vegetative growth
Cool period during flowering
Presence of soybean cyst nematode
Crop rotations – inconsistent

16. Impact of Planting Date
Disease Index (DX)
Date Rated

17. Impact of Planting Date 2009 – SDS Variety Trials
Valmeyer, IL planted 4/24
Havana, IL planted 4/26
Both fields have a history of SDS.

18. Impact of Planting Date 2009 – SDS Variety Trials
Carbondale, IL planted 5/20
Paris, IL planted 5/29
Both fields have a history of SDS, Carbondale was also infested with the pathogen.

19. Chemical Control Current fungicides do not limit SDS in the field
Some fungicides impact severity in greenhouse trials
Herbicides can reduce symptom severity in the field
Lactofen (X.B. Yang, Iowa State U.)
Experimental products
Generally, short lived reduction
Induced resistance, affecting toxin movement or expression, ?

20. Chemical Control
Could a product provide short-term protection to mirror that observed with delayed planting?
Seed Care trials with
Scott Cully, Syngenta R&D
- Havana and Valmeyer
- Fungicide/Nematicide trts.

21. Compacted Soils Vick et al. 2005. Canadian J. of Plant Path. 28:77-83.
Vick et al Plant Dis. 87:

22. Pathogen Research
Identification of fungal genes involved in the development of SDS
Karyotyping (Chromosomal organization)
SDS-SCN interaction
A. Fakhoury, Southern Illinois U.

23. Pathogen Research Generate REMI mutants
~800 mutants have been generated so far
Mutants screened for conidiation and growth pattern
Generate and collaborate to generate sequence material
Necessary in identifying targets for disruption
Expedite gene disruption
Permits genomic and comparative genomic studies (complements karyotyping, population studies…)

24. Tools Developed Optimize transformation system
Optimize site directed mutagenesis
A split-maker approach is being tested to disrupt genes
Several genes are being targeted at this point
Snf1, grx, fsr1 and several kinases
A GFP expressing strain of the pathogen was produced

25. Objectives
Identification of fungal genes involved in the development of SDS
Identification and characterization of pathways involved in virulence and pathogenesis
Detection of the karyotypic variation among F. virguliforme isolates

26. Karyotypic Variation Among Isolates
F. virguliforme has 11 chromosomes
We estimate the size of the genome at ~ 33 Mbp
Tested isolates exhibited polymorphism (differences) in terms of the sizes of their chromosomes
This polymorphism may be linked to the varying levels of aggressiveness exhibited by different isolates of the pathogen
GTBM is Germ tube burst method. It is another way to visualize chromosomes
Mapping in the pathogen
Polymorphism? What does it mean
Stress the fact that this is our data
Chromosomes of each of the F. virguliforme isolates, Iowa07, Carmi07, Mont-1, ARC07, AF06 and Vick07 were separated by PFGE. A combination of two different electrophoresis conditions were optimized and used to separate and resolve fungal chromosomes. The size and number of the separated chromosomes were determined based on the assumption that there is a linear relationship between chromosome size and migration distance on the gel. PFGE performed under conditions optimized for the separation of small to medium size chromosomes revealed five bands for each isolate ranging in size between Mbp. Two of these bands, with estimated sizes of 1.6 and 2.2 Mbp, were present in all the isolates included in this study (FIG. 1). One band, with an estimated size of 0.8Mbp and two bands with estimated sizes of 1.2 and 1.3 Mbp were resolved in isolates Vick07, Carmi07, ARC07 and AF06. Three bands ranging in size between Mbp were resolved exclusively in the isolates Mont1 and Iowa07.
Under conditions optimized for the separation of large chromosomes, four chromosomes in the size range Mbp were observed for all isolates in this study (FIG. 2). PFGE data for all chromosomes identified is compiled in FIG 3. PFGE revealed that F. virguliforme isolates have nine chromosomes and an estimated genome size of Mbp.
Nectria 40 Mbp
Soybean 1.1–1.15 Gb
Human 750 Mbp
SCN 100Mbp
GTBM

27. SDS interactions with SCN
Synergistic –
Roy et al., greenhouse
McLean and Lawrence, greenhouse
Rupe et al., 1991, field trials
Hershman et al., 1990, field trials
Xing and Westphal, 2006, microplots
Additive
Gao et al., greenhouse

28. Distribution of SCN
Source: G. Tylka, ISU

29. SDS and SCN

30. SDS and SCN
SCN juvenile and mycelium of F. virguliforme

31. Could Other Nematodes Be Involved?
SDS
Root knot nematode
M. incognita

32. Greenhouse trial
 Soybean cultivars were selected that differed for resistance to SCN, RKN, or SDS
Each cultivar was challenged with the GFP- expressing virulent Fv transformant, the GFP- expressing avirulent Fv transformant, or several nematode/fungus co-inoculations
The experiment consisted of 36 treatments replicated 5 times

33. Cultivar
H. glycines
M. incognita
F. virguliforme
Forrest R
P94M50 S
Spencer
GH3983 LS

34. H. glycines M. incognita F. virguliforme R S
Avirulent Fv
Avirulent Fv + SCN
Cultivar
H. glycines
M. incognita
F. virguliforme
Forrest R
P94M50 S
Spencer
GH3983 LS

35. H. glycines M. incognita F. virguliforme R S
Avirulent Fv
Avirulent Fv + SCN
Cultivar
H. glycines
M. incognita
F. virguliforme
Forrest R
P94M50 S
Spencer
GH3983 LS

36. Host Resistance Quantitative resistance Controlled by multiple genes
Difficult to test in the field

37. Host Resistance Mapped genes from PI 567374 in greenhouse.
Genes on linkage group D2 and I.
Mapped genes from Ripley in field with SSR markers using field data.
Genes on linkage group D2 and L.
Genes have been confirmed and are conducting marker-assisted backcrossing
B. Diers
B. Diers and M. Schmidt
B. Diers

38. Evaluating Resistance to SDS
Illinois Soybean Association
SDS Commercial Variety Trial
USDA Uniform and Regional Trials
North Central Soybean Research Program
NC Regional Trial

39. Success equals ?
A successful trial has a mean DX of at least 15 – 20 in susceptible check varieties.

40. Factors That Insure Success
Field with history of SDS and/or inoculation when needed
Early planting
Irrigation
Disease evaluation at R6
Appropriate check varieties
for the maturity group
A good rating scale

41. SDS Variety Trials Over 1,800 varieties (includes Public Lines) MG 1-5
Six locations overall
3-4 for each MG
Over 16,000 plots
Results distributed via , Websites, Mail, Popular press, Companies

42. Variety Performance in 2009
Relative DX
Rating
Percentage of Entries MG MG
0-20
Res. 6 5
21-40
Mod. Res. 17
41-60
Mod. Susc. 23 32
61+
Susc. 54 46

43. Greenhouse Assays Benefits/Limitations More art than science
Agreement with known field reactions
Hashmi obtained correlation of .80
Collaborative university trials – Several blind trial competitions yielded correlations
Hashmi et al Plant Health Progress doi: /PHP RS.

44. Waterbath Method

45. Tray Method
Pictures – R. Bowen, UIUC

46. Pictures – R. Bowen, Univ. of Illinois
1 –Typical plant, showing no symptoms.
3 – Leaf with obvious, inter-veinal chlorosis
Pictures – R. Bowen, Univ. of Illinois

47. Pictures – R. Bowen, UIUC

48. Wish List Resistant commercial varieties and public germplasm
Chemical treatments – seed, foliar, in-furrow
Factors that contribute to severe disease
Increased resolution and consistency in field trials
More efficient greenhouse/laboratory screening assays

49. Summary

50. Questions?
Jason P. Bond