Flower Biology and

Biologically-based

Integrated Fire Blight

Management

Dr. Larry Pusey

USDA-ARS, Wenatchee, WA

WSHA Annual Meeting, Dec. 6, 2011

Notes on slides can be viewed by holding the cursor over the

icon in the upper left corner.

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Why biological control?

• Replace antibiotics

• Complement other approaches

• Advantage of multiplication

and spread

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Diagram of apple flower

Stigma

Style

Anther

Petal

Hypanthium

Filament

Sepal

Ovary

Ovule

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Apple stigma

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Stigma

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Erwinia amylovora (Ea)

on flower stigma

14

12

10

8

CFU per day

(x 100,000)

6

4

2

0

0 4 8 12 16 20 24 28 32 36 40 44

Temperature (°C)

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Flower stigma age and bacterial colonization

0 4

Days

8

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Ea and beneficial bacteria on ‘Gala’ stigmas

8

related to flower age

Ea

Log CFU

6

4

A506

E325

2

0 2 4 6 8 10 12 14

Day

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Hypanthium

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Hypanthium

A

B

C

D

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Water relations and Ea in hypanthium

Nectar

Sugar (%)

Population

(Log CFU)

Disease (%)

60

40

20

0

80 85 90 95 100

RH (%)

7

6

5

4

3

-8 -6 -4 -2 0

Nectar Ψ w

(MPa)

100

80

60

40

20

0

-3 -2 -1

Ovary Ψw

(MPa)

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Growth of microbial strains

in synthetic nectar (25% sugar)

7

6

5

4

Yeasts

Erwinia

Pantoea

Bacillus

Pseudomonas

3

2

1

0

E583

Ea153

E19

87-80

87-66

87--70

PD494

88-38

E6

C106

C9-1

F257

E325

Eh252

F468

87-167

E300

E873

F207

F143

F113

A506

F516

E326

E198

F395

F224

F301

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Survey of natural microbial populations

on ‘Gala’ flowers

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Bacteria and yeast genera on apple flowers

Bacteria

Acinetobacter

Actinobacterium

Aeromicrobium

Arthrobacter

Bacillus

Cellulomonas

Clavibacter

Curtobacterium

Erwinia

Kocuria

Microbacterium

Micrococcus

Pantoea

Paenibacillus

Pectobacterium

Pseudomonas

Ralstonia

Rhodococcus

Rhizobium

Stenotrophomonas

Variovorax

Yeasts

(or yeast-like)

Aureobasidum

Cryptococcus

Pichia

Rhodotorula

Starmerella

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Crab apple

laboratory

model

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Screening

microorganisms

for potential use

in biological control

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Bacteria and yeast genera on apple flowers

Bacteria

Acinetobacter

Actinobacterium

Aeromicrobium

Arthrobacter

Bacillus

Cellulomonas

Clavibacter

Curtobacterium

Erwinia

Kocuria

Microbacterium

Micrococcus

Pantoea (1)

Paenibacillus

Pectobacterium

Pseudomonas (2)

Ralstonia

Rhodococcus

Rhizobium

Stenotrophomonas

Variovorax

Yeasts

(or yeast-like)

Aureobasidum (2)

Cryptococcus (1)

Pichia

Rhodotorula

Starmerella

*Red indicates highest

ranked groups in

screening assays

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Adaptability of bacteria and yeasts

on flower tissues

Bacteria

• Stigma

• Young flowers

Yeasts

• Hypanthium

• Old flowers

Practical implication

• Bacterial biocontrol agents should be applied

beginning in early bloom

• Application of yeasts may be delayed

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Proposed future strategies

I. Bacterial biocontrol

II. Yeast biocontrol

III. Integrated management

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I. Bacterial biocontrol

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Microencapsulation to improve

survival and dispersal

Collaborators: K. Kim & H. Choi, Univ. Illinois

200 µm

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Exploit metabolites

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Exploit bacteriophages

Collaborator: A. Svircev, AAFC, Ontario

Phage + carrier

Carrier

bacterium is

Pantoea

agglomerans

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II. Yeast biocontrol

• Hypanthium screening

• Assess osmotolerance

• pH consideration

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III. Integrated management

• Complementary biocontrol

• Agents with antibiotic-like activity

(e.g., AMPs)

• Plant resistance inducers