Goss’s wilt: Get the facts!

Alison RobertsonCharlie Hurburgh

Lisa ShepherdCharlie Block

and Roger Elmore

21 July 2 August 25 August

Goss’s leaf blight disease progress

9 September

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

Usually first seen on top leaves

Q. What symptoms occur with Goss’s wilt?

May be seen in mid canopy

Q. What symptoms occur with Goss’s wilt?

Wavy, marginGreasy “Freckles”

Q. What symptoms occur with Goss’s wilt?

“Freckles”

Saprophytic fungi

Q. What symptoms occur with Goss’s wilt?

Q. Is there a kit to diagnose Goss’s wilt?

Clavibacter michiganensis subsp michiganensis

Cost:5 for $32.5025 for $120

5-10 minsImmunoStrip Test (Agdia®)

CAREFUL!!!!!

— False positives

example: Purple leaf sheath; other saprophytic bacteria on corn.

— Extremely sensitive

cross contamination between samples

Purple leaf sheath

Q. Is there a kit to diagnose Goss’s wilt?

ICM 2008

Q. Has a new race of Cmn evolved?

Race: a subgroup or biotype within a species

Usually distinguished from other races by virulencesymptom expressionor host rangebut not by morphology

(D’ Arcy et al. 2001)

ICM 2008

Q. Has a new race of Cmn evolved?

1a 1b 1c 1k 2 3a

3b 3c 4 5 6 7 8

1d C

Standardized soybean lines are used to identify races of P. sojae

ICM 2008

Q. Has a new race of Cmn evolved?

Rpp9 resistance to Southern rust fungus Puccinia polysora

Photo courtesy of B. Dolezal, Pioneer

ICM 2008

Q. Has a new race of Cmn evolved?

Ht1 resistance to Northern leaf blight fungusHelminthosporium turcicum

Race 1 Race 0

Photos courtesy of B. Dolezal, Pioneer

ICM 2008

Q. Has a new race of Cmn evolved?

― 131 strains of Cmn

• 1969 – 2009

• origin

ICM 2008

― 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)

Cmn bacteria ooze from residue; splash

dispersed

Bacteria overwinter in infested crop

residue and seed

Goss’s disease cycleSymptoms

Epiphytic infection

Infection

― Goss’s wilt bacterium survives for at least 10 xximonths in infested surface crop residue

― Survival is significantly reduced in buried residue

0” 4” 8”Leaves 80 0 0Stalks 75 30 40Cobs 63 5 0Pure culture 0 0 0

Goss’s Disease Index

(Schuster, 1975)

Q. How long does Cmn survive in corn residue?

Can Cmn survive longer?

Survival C. m. subsp. michiganensis on tomato

Buried infested residue: ~7 months

Surface infested residue: 2 years Gleason et al., 1991

What effect might corn stover removal have?

Percent corn residue and GLS disease severity

de Zareno and Lipps, 1993

More residue = greater disease

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)

Biddle et al, 1990

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

Inoculated field trialLeaves of plants inoculated at V3, V6 and VTSeed infection: 17.1 - 30.7%Seed transmission: none detected (N=12000 seed)

Biddle et al., 1990

Q. Was Goss’s wilt introduced on Cmn-infected seed?

Natural infection in fieldSeed naturally infected with Goss’s wilt Seed infection: 2 – 39%Seed transmission: 1 in 12864 seedlings.

- single case found in 29% seed lotShepherd, 1999 & 2011

― Several common weeds are secondary hosts of Cmn

i. Green foxtail

ii. Shattercane

iii. Sudangrass

iv. Eastern gamagrass

Q. Are there other hosts of Cmn?

Schuster, 1975

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

Q. Are there other hosts of Cmn?

— Several genes

— quantitatively inherited

— not complete, i.e. no immunity known

—either leaf blight or wilt

Q. Is there resistance to Cmn?

115 bu/acre yield difference

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

r=0.61 P=0.01

Robertson et al., 2011

Goss’s leaf blight severity and stalk rot

Variable <5% at R5 >5% at R5 P value

# rows 16.4(14.5-18.6)

16.9(15.3-17.9) 0.175

# kernels per row 31.9(29.2-34.6)

31.5(29.7-32.6) 0.286

Seed weight (g/1000)

402.4(327.8-472.0)

327.8(245.2-395.6) 0.0001

Robertson et al., 2011

Effect of Goss’s leaf blight on grain characteristics

Assessment <5% at R5 >5% at R5 P value

Test Weight @ 15% moisture (lb/bu)

57.0(55.2-60.3)

55.7(53.6-60.6) 0.049

Starch (%) 60.8(60.1-61.8)

61.3(60.7-62.1) 0.041

Protein, oil and density: NS

Robertson et al., 2011

Effect of Goss’s leaf blight on grain characteristics

r=-0.51 P=0.007

Robertson et al., 2011

8 hybrids

Goss’s leaf blight severity and seed size

r=-0.77 P=0.001

Robertson et al., 2011

2 hybrids

Goss’s leaf blight severity and seed size

r=-0.87 P<0.001

Robertson et al., 2011

2 hybrids

Goss’s leaf blight severity and estimated yield loss

Goss’s leaf blight severity and test weight

r = - 0.83 P=0.0002

Robertson et al., 2011

2 hybrids

Goss’s leaf blight severity and seed infectionGoss's

severity (%)Growth

stage Seed Infection Seed Transmission (positive/ tested)

1 R35 R55 R35 R55 R5

15 R320 R5.2520 R335 R5.75

100 R5.5100 ~R5

Goss’s leaf blight severity and seed infectionGoss's

severity (%)Growth

stage Seed Infection Seed Transmission (positive/ tested)

1 R3 0/2005 R55 R3 0/2005 R5 0/2005 R5 0/200

15 R3 0/20020 R5.2520 R3 0/20035 R5.75 0/145

100 R5.5 1/145100 ~R5 10/400

Goss’s leaf blight severity and seed infectionGoss's

severity (%)Growth

stage Seed Infection Seed Transmission (positive/ tested)

1 R3 0/2005 R5 0/7555 R3 0/2005 R5 0/2005 R5 0/200

15 R3 0/20020 R5.25 0/76820 R3 0/20035 R5.75 0/145 0/1154

100 R5.5 1/145 0/1233100 ~R5 10/400 0/760

Risk factors for Goss’s wilt and leaf blight

Susceptible hybrid

Continuous corn

Percent surface residue

Goss’s wilt in 2011

(Severe storms)

Management in 2012

Resistant hybrid

Rotation

Residue management

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