Hear an update on the latest research on Soybean Sudden Death Syndrome.

1. Soybean Sudden Death Syndrome:
Research Update
Leonor Leandro, Dept. Plant Pathology, ISU
Linda Kull, National Soybean Research Laboratory, IUCU
Crop Advantage Series 2011

2. Outline
• Overview of SDS symptoms and impact
• New knowledge about the pathogen
– Toxins and pathogenicity genes
• Conditions that favor SDS
– Moisture
– Microbial interactions
• Disease Management
– New genetics
– Cultural practices

3. SDS Leaf Symptoms
• Yellow and brown spots or streaks
between the veins
• Defoliation leaving petioles
attached to the stems

4. SDS Root Symptoms
• Reddish-brown to gray rot
in internal tap root tissue
• Poor lateral root growth
• Blue spore masses may be
visible on root surface

5. SDS distribution and yield loss in US (2006-2008)
IA
(1993)
AR
(1971)
Estimated yield
Loss (Mbu)
(Raw data provided by A. Wrather)

6. SDS in 2010 Yield loss estimate: 28 MBu

7. The SDS Pathogen
• Soilborne fungus
• Species: Fusarium virguliforme
• Produces sickle-shaped spores
that are blue in mass
• Produces round-shaped survival
spores called chlamydospores

8. SDS Disease Cycle
High soil moisture
Toxins moved
Symptoms
to leaves
develop
Plants die
Cool soil temperature
High moisture
Overwinters in
soil, plant Fungus
debris, and SCN colonizes
cysts Spores infect roots roots
of young plants

9. When do infections occur?
• Can occur as early as seed germination
• Older seedlings are more resistant
Seedling age
Root Rot Severity (AUDPC)
2500 at inoculation
2000 0 DAP
1500 3 DAP
1000 7 DAP
500 13 DAP
0
63
17 73
23 84
29
Temperature ( F)
Source: Gongora-Canul and Leandro, ISU

11. Why are older seedlings less susceptible to SDS?
Infected 3 days after Infected 14 days after
planting plating
Xylem
Cortex
Source: Gongora-Canul and Leandro, ISU

12. Approaches to Identify
Candidate Pathogenicity Genes
Madan Bhattacharyya, ISU
• Transcriptomic: Based differential
expression of genes in infected tissues vs.
mycelia and germinating spores.
• Proteomics: Proteome of the xylem sap of
infected soybean seedlings
• Metabolomics: Metabolites of diseased and
healthy soybean leaves
Source: Bhattacharyya, ISU

13. Detected transcripts for 97.5% of the14,845 F.
virguliforme genes . Less than 100 genes expressed
in infected tissues only
100%
90%
80%
70%
60% Not expressed
50%
Expressed
40%
30%
20%
10%
0%
Source: B. Sahu and M. Bhattacharyya, ISU

14. 25 of the gene transcripts detected only in the F.
virguliforme infected soybean roots are:
12 genes encode enzymatic functions 13 have unknown functions.
Elastinolytic metalloproteinase Mep Stress responsive A/B barrel domain protein
Monooxygenase FAD-binding protein FAD binding domain-containing protein
Pisatin demethylase MFS transporter
Pectate lyase FAD binding domain-containing protein
Hypothetical protein FOXB_14311
Serine protease inhibitor
Hypothetical protein FOXB_02038
Endo-1,4-beta-xylanase
Exopolygalacturonase Hypothetical protein FOXB_05665
Glycosyltransferase Hypothetical protein FOXB_10278
Hypothetical protein FOXB_09766
Lignostilbene dioxygenase
Hypothetical protein FOXB_10941
Gibberellin 3-beta hydroxylase
Predicted protein
Cellulase
Hypothetical protein FOXB_13583
Fungal cellulose binding domain
protein Hypothetical protein FOXB_09991
Hypothetical protein FOXB_10941
Source: B. Sahu and M. Bhattacharyya, ISU

15. Identification of fungal genes and pathways
involved in the development of SDS
Source: Fakhoury & Bond, SIUC
• Genes involved in early
events in pathogenesis –
Hydrolases (Fvsnf1,…)
• Genes facilitating the
colonization of host tissue –
Kinases (Fvfsr1, Fvpmk1,…)
• Genes involved in tolerance
of antimicrobial compounds
produced by the host
(Fvgrx2, Fvtrx1,…) S. Mansouri
15
Source: Fakhoury & Bond, SIUC

16. Disruption of Fvfsr1 in F. virguliforme affects
the aggressiveness of the pathogen
A
Control WT ΔFvfsr1
B
10 8 5
9 7
Mean(Amount of DNA in ng)
4
8
7 C 6
D 3
Forest
Foliar ratings (ds)
Foliar ratings (ds)
6 5 2
5 4
1
4 3
Variety
0
3 2 5
2
1
1
Mean(Amount of DNA in ng)
4
0 0
3
Spencer
-1 -1
Control F14 Mont-1 Each Pair Control F14 Mont-1 Each Pair 2
Student's t Student's t
1
Treatments 0.05 Treatments 0.05
0
Spencer (Susceptible soybean Forest (Resistant soybean
Mont-1 Control F14
T reatments
cultivar) cultivar )
F. virguliforme level in infected soybean
(Mont-1 (WT), F14 (ΔFvfsr1) and control roots of wild type (Mont-1), ΔFvfsr1
(no fungus) four weeks after planting (F14) and control (no fungus)
16
Source: Fakhoury & Bond,Bond, SIUC
Fakhoury & SIUC

17. Favorable Conditions for SDS
• High soil moisture
• Cool temperatures
• Soil compaction
• Plant stress - SCN

18. Does high soil moisture favor SDS?
• SDS epidemic years are usually wetter, especially in June
SDS Total Precipitation (inches)
Year Incidence Apr May Jun Jul Aug
2007 Low 4.3 5.3 3.5 3.1 9.1
2008 High 5.6 5.5 8.9 5.5 1.7
2010 Very high 3.8 4.6 10.3 8.1 4.5
2011 Low 3.0 4.5 4.9 3.5 1.7
Mean High 4.3 4.9 8.7 6.9 4.5
Mean Low 3.4 5.9 4.1 3.3 5.1
Mean 30-year 3.0 4.1 4.6 3.8 3.8
Source: Robertson, Mueller, and Leandro, ISU

19. When is soil moisture most important?
Irrigation field trial, Ames, 2011
50
46.2 bu/ac
SDS Severity (%)
40
V5-R6
30 50.2
R1-R6
20 R3-R6
10 55
No irrigation
47.6
0
Susceptible Resistant
Soybean Variety
Source: Leandro, ISU

20. Are cool seasons more favorable for SDS?
• SDS epidemic years are generally cooler
• No consistent trend for cool temperatures at planting
SDS Soil Temperature oC (F)
Incidence Apr May Jun Jul Aug
High SDS 9.0 16.1 21.1 24.7 24.1
(48.2) (61) (70) (76.4) (75.4)
Low SDS 11.1 17.4 23.3 26.9 25.1
(51.8) (63.3) (73.9) (80.4) (77.2)
30-year 9.8 16.3 22.1 25.1 24.1
(49.6) (61.3) (71.8) (77.2) (75.4)
Source: Robertson, Mueller, and Leandro, ISU

21. Do other soil microbes interact with SDS?
• Soybean Cyst Nematode (SCN)
• SDS appears earlier and is
more severe with SCN
• Pathogens may spread
together

22. What soil factors lead to SDS hotspots?
Fakhoury and Bond (SIU), Malvick (UMN), Leandro (ISU)
• No differences between hotspots and healthy
spots:
– Soil abiotic properties (N, P, K, org. matter, texture, etc)
– SCN density
• Differences found in microbial populations
– F. virguliforme density in soil
– Diversity of fungal communities
– Diversity of nematode communities
Source: Fakhoury (SIU)

23. What soil factors lead to SDS hotspots?
Cultured independent approaches-PCR DGGE (IL)
DGGE was used to screen for polymorphism in
Soil samples banding patterns between samples:
 Fungal ITS DGGE fingerprint for IL soil
Isolate DNA
DGGE Species
Identification
by sequencing
Source: Fakhoury, SIU

24. Soybean Resistance to SDS
• Controlled by many genes
• Quantitative/partial resistance
– No soybean variety is immune to SDS
• Two independent resistance mechanisms
– Root resistance / foliar resistance

25. Is there foliar resistance to pathogen toxins?
• Tested with pathogen culture filtrate assay
Source: Leandro, ISU

26. Some soybean lines have resistance to toxins
Source: Leandro, ISU

27. Identification of soybean resistance genes
using VIGS
Whitham, Hill, Leandro (ISU); Radwan, Clough (UIUC)
30
Inoculate with a LSD=9.6 3C12-1
virus vector 25
containing gene 3D7-1
SDS severity (%)
of interest 20 3D10-1
Radwan, UIUC 3F5-5
15
Jar-1
10 b
Coi-1
b b
5 b H-92
Expose plants to b b
b
F. virguliforme 0
Mock-V2
culture filtrates
Radwan, UIUC

28. Can we expect better resistance in the future?
• Yes.
• Breeders are searching
for new sources of SDS
resistance
• Incorporating
resistance genes into
earlier MG

29. Germ release AR10SDS MGI (early)
AR10SDS: Ripley x IA1008- Ripley MG IV; IA1008 MG I
Line DI DI SCN IDC Yield
Field Gh
HGT7 HGT 2.5.7 bu/a
R3 R1
AR10SDS 2 1 R NR 2-4 51
IA1008 3-4 52
MN 1606 10 2
Suscept. 20 10
Silvia Cianzio, ISU

30. Germ release AR11SDS MG II
AR11SDS: Ripley x IA2036 - Ripley MGIV, IA2036 MGII
Line DI DI SCN IDC Yield
Field Gh
HGT7 HGT bu/a
R3 2.5.7
R1
AR11 SDS 0 R LR 2-3 58
Dwight 1 R MR 3 59
SDS Res. 5
SDS Susc. 15
Silvia Cianzio, ISU

31. New populations for developing resistant lines
Population Susceptible Resistant # Sub- # of
ID parent parent popul. RIL
Screened:
SDS, SCN, and
AX19286 A95- LS94-3207** 11 391 molecular
684043* screening
AX19287 A95-684043 LS98-0582** 10 435
AX19286 (A95-
AX19288 A95-684043 LS99-2235** 1 392
684043 X LS94-
3207):
AX19289 IA1006*** LS94-3207 4 446
o 20 highly SDS
resistant (3
AX19290 IA1006 LS98-0582 3 471 protocols)
o 15 also are
AX19291 IA1006 LS99-2235 1 85 highly resistant
to SCN
AX19294 IA2050 LS94-3207 8 461
*- SCN resistant ; ** - SDS resistant ; ***- BSR resistant
Cianzio and Bhattacharyya, ISU

32. Does tillage help reduce SDS?
Year, Foliar Root Yield
tillage AUDPC colonization (%) (Kg/ha)
2000
Disk 47 a 49 a 2850 b
No-till 39 a 48 a 2973 b
Chisel 24 b 61 b 3258 a
2001
Disk 149 b 61 b 3324 a
No-till 329 a 67 a 3081 b
Chisel 185 b 71 a 3244 a
Vick et al. (2006)

33. Effects of planting date and tillage
***
NS
NS
*** *** NS
Wrather et al, 1995

34. Effects of planting date and tillage
***
NS
NS
*** *** NS
Wrather et al, 1995

35. Effects of planting date and tillage
***
NS
NS
*** *** NS
Wrather et al, 1995

36. Should planting be delayed to manage SDS?
• No! Delayed planting can risk yield potential
• Plant fields with history of SDS last
Planting Date
Crop Advantage Series 2010 Palle Pedersen, ISU

37. Do seed treatments work against SDS?
• No
• Commercially available seed treatments are
currently not effective
• New products are being tested

38. How about rotation with other crops?
• Previous research is inconclusive
• Current research at ISU shows promise
M. Liebman, L. Leandro, A. Robertson, C. Chase, D. Mueller
3-year rotation / 2-year rotation
Photo courtesy of L. Miller

39. Crop rotation study (ISU, 2010)
SDS Incidence SDS Severity
100 A 100 A
K287RR K287RR
80
SDS incidence (%)
SDS Severity (%)
80 K2918
K2918
60
B
60
a B
40 40
a
20 20 b b
b B b B
0 0
S2 S3 S4 S2 S3 S4
Rotation Treatments YIELD (Bu/Acre)
S2 corn-soybean Rotation K-287RR K-2918
S3 corn-soybean-oat/red clover S2 42 22
S4 corn-soybean-oat/alfalfa - alfalfa
S3 54 55
S4 55 53
Leandro, Liebman, Robertson, M
r, Chase, ISU

40. Funding sources

41. Questions?