1. Goss’s wilt: Get the facts!
Alison Robertson
Charlie Hurburgh
Lisa Shepherd
Charlie Block
and
Roger Elmore

2. Goss’s leaf blight disease progress
21 July
2 August
25 August
9 September

3. Q. Where was Goss’s wilt in Iowa in 2011?

4. Q. What symptoms occur with Goss’s wilt?
Usually first seen on top leaves

5. Q. What symptoms occur with Goss’s wilt?
May be seen in mid canopy

6. Q. What symptoms occur with Goss’s wilt?
Greasy “Freckles”
Wavy, margin

7. Q. What symptoms occur with Goss’s wilt?
Saprophytic fungi
“Freckles”

8. Q. Is there a kit to diagnose Goss’s wilt?
Clavibacter michiganensis subsp michiganensis
ImmunoStrip Test (Agdia®)
Cost:
5 for $32.50
25 for $120
5-10 mins

9. Q. Is there a kit to diagnose Goss’s wilt?
CAREFUL!!!!!
False positives
example: Purple leaf sheath; other saprophytic bacteria on corn.
Extremely sensitive
cross contamination between samples
Purple leaf sheath

10. Q. Has a new race of Cmn evolved?
Race: a subgroup or biotype within a species
Usually distinguished from other races by
virulence
symptom expression
or host range
but not by morphology
(D’ Arcy et al. 2001)
ICM 2008

11. Q. Has a new race of Cmn evolved?
Standardized soybean lines are used to identify races of P. sojae 1a 1b 1c 1k 2 3a 3b 3c 4 5 6 7 8 1d C
ICM 2008

12. Q. Has a new race of Cmn evolved?
Rpp9 resistance to Southern rust fungus Puccinia polysora
Photo courtesy of B. Dolezal, Pioneer
ICM 2008

13. Q. Has a new race of Cmn evolved?
Ht1 resistance to
Northern leaf blight fungus
Helminthosporium turcicum
Race 1
Race 0
Photos courtesy of B. Dolezal, Pioneer
ICM 2008

14. Q. Has a new race of Cmn evolved?
131 strains of Cmn
1969 – 2009
origin
ICM 2008

15. A: no correlation with strain, xxiorigin, history
Two groups: A and B
A: no correlation with strain, xxiorigin, history
B: all strains collected after 1999
13/69 strains = <20%
(Agrakova et al., 2011)
ICM 2008

16. Goss’s disease cycle Symptoms
Bacteria overwinter in infested crop residue and seed
Infection
Cmn bacteria ooze from residue; splash dispersed
Epiphytic infection

17. Q. How long does Cmn survive in corn residue?
Goss’s wilt bacterium survives for at least 10 xximonths in infested surface crop residue
Survival is significantly reduced in buried residue
Goss’s Disease Index 0” 4” 8”
Leaves 80
Stalks 75 30 40
Cobs 63 5
Pure culture
(Schuster, 1975)

18. Can Cmn survive longer?

19. Survival C. m. subsp. michiganensis on tomato
Buried infested residue: ~7 months
Surface infested residue: 2 years
Gleason et al., 1991

20. What effect might corn stover removal have?

21. Percent corn residue and GLS disease severity
de Zareno and Lipps, 1993
More residue = greater disease

22. What effect does manure have on survival of Cmn?
Population of C.m. subsp. sepedonicus on potato decreased as other microbes in cattle manure slurry increased
(Roozen and Vanvuurde 1991)
Composts amended with cattle or poultry manure reduced C. m. subsp. michiganensis of tomato (tomato canker) by 79 to 100%
Populations of C. m. subsp. michiganensis in composts declined to undetectable levels in 15 to 21 days
(Yogev et al, 2009)
Looking at potato tubers spreading ring rot of potato. Work done in Netherlands – no ring rot reported their. Pigs and cows eat tubers – if tubers are infected – could introduce.pathogen

23. Q. Was Goss’s wilt introduced on Cmn-infected seed?
Seedborne infection (seed infection): pathogen carried on or in a seed
Seed transmission: pathogen in or on seed infects developing seedlings
Biddle et al, 1990

24. Q. Was Goss’s wilt introduced on Cmn-infected seed?
Inoculated field trial
Leaves of plants inoculated at V3, V6 and VT
Seed infection: %
Seed transmission: none detected (N=12000 seed)
Biddle et al., 1990
Natural infection in field
Seed naturally infected with Goss’s wilt
Seed infection: 2 – 39%
Seed transmission: 1 in seedlings.
- single case found in 29% seed lot
Shepherd, 1999 & 2011
Biddle et al, 1990

25. Q. Are there other hosts of Cmn?
Several common weeds are secondary hosts of Cmn
Green foxtail
Shattercane
Sudangrass
Eastern gamagrass
Schuster, 1975

26. Q. Are there other hosts of Cmn?
Other susceptible hosts: sugarcane –atypical symptoms
Resistant to infection:
Oats
Barley
Wheat
Bromegrass
Orchardgrass
Crabgrass
Barnyard grass
Proso millet
Yellow foxtail
Johnson grass
Sugarbeet
cabbage
Chrysanthemum
Poinsettia
Tomato
Petunia
Potato
Schuster, 1975

27. Q. Is there resistance to Cmn?
Several genes
quantitatively inherited
not complete, i.e. no immunity known
either leaf blight or wilt
115 bu/acre yield difference

28. Effect of Goss’s leaf blight on grain characteristics
9 fields
7 in Central IA; 2 in SW Iowa
8 hybrids from 3 major seed companies
2 to 11 locations per field
Goss’s leaf blight severity at R3 or R5
Stalk rot severity prior to harvest
20 ears hand harvested per location

29. Goss’s leaf blight severity and stalk rot
r=0.61 P=0.01
Robertson et al., 2011

30. Effect of Goss’s leaf blight on grain characteristics
Variable
<5% at R5
>5% at R5
P value
# rows
16.4
( )
16.9
( )
0.175
# kernels per row
31.9
( )
31.5
( )
0.286
Seed weight (g/1000)
402.4
( )
327.8
( )
0.0001
Robertson et al., 2011

31. Effect of Goss’s leaf blight on grain characteristics
Assessment
<5% at R5
>5% at R5
P value
Test 15% moisture (lb/bu)
57.0
( )
55.7
( )
0.049
Starch (%)
60.8
( )
61.3
( )
0.041
Protein, oil and density: NS
Robertson et al., 2011

32. Goss’s leaf blight severity and seed size
r= P=0.007
8 hybrids
8 hybrids
Robertson et al., 2011

33. Goss’s leaf blight severity and seed size
r= P=0.001
2 hybrids
These two hybrids are very closely related – one is RR and one is triple stack but they both have the same background genetics
Robertson et al., 2011

34. Goss’s leaf blight severity and estimated yield loss
2 hybrids
r= P<0.001
Note – I also dropped the 100% severity from this – then r = 0.66 P=0.02
Robertson et al., 2011

35. Goss’s leaf blight severity and test weight
2 hybrids
r = P=0.0002
Robertson et al., 2011

36. Seed Transmission (positive/ tested)
Goss’s leaf blight severity and seed infection
Goss's severity (%)
Growth stage
Seed Infection
Seed Transmission (positive/ tested) 1 R3 5 R5 15 20
R5.25 35
R5.75
100
R5.5
~R5

37. Seed Transmission (positive/ tested)
Goss’s leaf blight severity and seed infection
Goss's severity (%)
Growth stage
Seed Infection
Seed Transmission (positive/ tested) 1 R3
0/200 5 R5 15 20
R5.25 35
R5.75
0/145
100
R5.5
1/145
~R5
10/400

38. Seed Transmission (positive/ tested)
Goss’s leaf blight severity and seed infection
Goss's severity (%)
Growth stage
Seed Infection
Seed Transmission (positive/ tested) 1 R3
0/200 5 R5
0/755 15 20
R5.25
0/768 35
R5.75
0/145
0/1154
100
R5.5
1/145
0/1233
~R5
10/400
0/760

39. Risk factors for Goss’s wilt and leaf blight Percent surface residue
Susceptible hybrid
Continuous corn
Percent surface residue
Goss’s wilt in 2011
(Severe storms)

40. Management in 2012
Resistant hybrid
Rotation
Residue management

41. Thanks for attending!
What questions do you have?