Life without antibiotics: understanding flower biology in the ...

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.

Why biological control?
• Replace antibiotics
• Complement other approaches
• Advantage of multiplication
and spread

Diagram of apple flower
Stigma
Style
Anther
Petal
Hypanthium
Filament
Sepal
Ovary
Ovule

Apple stigma

Stigma

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)

Flower stigma age and bacterial colonization
0 4
Days
8

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

Hypanthium

Hypanthium
A
B
C
D

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)

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

Survey of natural microbial populations
on ‘Gala’ flowers

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

Crab apple
laboratory
model

Screening
microorganisms
for potential use
in biological control

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

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

Proposed future strategies
I. Bacterial biocontrol
II. Yeast biocontrol
III. Integrated management

I. Bacterial biocontrol

Microencapsulation to improve
survival and dispersal
Collaborators: K. Kim & H. Choi, Univ. Illinois
200 µm

Exploit metabolites

Exploit bacteriophages
Collaborator: A. Svircev, AAFC, Ontario
Phage + carrier
Carrier
bacterium is
Pantoea
agglomerans

II. Yeast biocontrol
• Hypanthium screening
• Assess osmotolerance
• pH consideration

III. Integrated management
• Complementary biocontrol
• Agents with antibiotic-like activity
(e.g., AMPs)
• Plant resistance inducers