RACHEL MELNICKANISSA POLEATEWICHDEPARTMENT OF PLANT PATHOLOGYPENN STATE UNIVERSITY
FIELD EVALUATION OF ENDOPHYTES FOR
MANAGEMENT OF WITCHES’ BROOM ON CACAO
Department of Plant Pathology
Previous work
INIAP station in Pichilingue Ecuador
Isolated endophytic bacteria from elite cacao trees escaping disease
Screened isolates at Penn State to determine which bacterial endophytes to study further
Growth chamber studies
Plants maintained in growth chambers
Detached leaf assays used to screen isolates
Colonized leaves challenged with pathogen
Ecuador field trials
Selected 4 bacterial isolates based on performance in growth chamber studies
Investigated foliar colonization of these bacteria on 5 genotypes of cacao in the field Susceptible (EE19 and IMC67) Tolerant (A2634 and A2126) High yielding and Resistant (CCN51)
Colonized foliage of small potted plants and placed under larger trees in May 2007
Bacterial Application
Colonization
TIME
Disease Challenge
Experimental System
Ecuador field trials
Disease challenge in Ecuador
Seedlings undergoing disease screening
Susceptible tree full of witches’ broom
Spores raining from infected
trees onto seedlings
Preliminary observations
Endophytic colonization occurred on all genotypes
Disease developed on seedlings Disease ratings are being taken monthly Preliminary data has been analyzed and
published in PDMR
Bacteria were re-applied to plants in November 2007, March 2008, and May 2008
Disease severity
One bacterial treatment has completely suppressed disease....as of March 2008
Bacterial Treatments
Control A2076 CCAT EET Cur3
AU
DP
C (
Dis
ease
Sev
erity
)
0
20
40
60
80
100
Disease severity
Tolerant genotypes have significantly less disease than susceptible genotypes
Cacao genotype
EET19 CCN51 A2634 A2126 IMC67
AU
DP
C (
Dis
ease
Sev
erity
)
0
20
40
60
80
100
Coupling tolerant genotypes with bacteria can reduce disease
Clone and Treatment Combinations
EE
T19
+ C
ontr
olE
ET
19 +
A20
76E
ET
19 +
CC
AT
EE
T19
+ E
ET
103h
tE
ET
19 +
CU
R3
CC
N51
+ C
ontr
olC
CN
51 +
A20
76C
CN
51 +
CC
AT
CC
N51
+EE
T10
3ht
CC
N51
+ C
UR
3A
2634
+ C
ontr
ol A
2634
+ A
2076
A26
34 +
CC
AT
A26
34 +
EE
T10
3ht
A26
34 +
CU
R3
A21
26 +
Con
trol
A21
26 +
A20
76A
2126
+ C
CA
TA
2126
+ E
ET
103h
tA
2126
+ C
UR
3IM
C67
+ C
ontr
olIM
C67
+ A
2076
IMC
67 +
CC
AT
IMC
67 +
EE
T10
3ht
IMC
67 +
CU
R3
AU
DP
C (
Dis
ease
Sev
erity
)
0
50
100
150
200
Future
Continuing INIAP trial…..Rachel is currently in Ecuador collecting data
Replicating field trial on the Nestle farm in Valencia, Los Rios, Ecuador
Inoculation of bacteria on established tree branches
Future
Molecular analysis (ARISA) of microbial populations to determine how application of biocontrol agents impacts native microbes
Molecular analysis (qPCR) of leaves to determine how endophytes affect plant defense pathways Real time PCR used to quantify mRNA to
determine the expression of genes in the plant
Related Projects
Management of postharvest disease on apple
Achieved 90% reduction in bitter rot severity in preliminary tests Adams county, PA
Experiment repeated in Bolivia Giovanna Plata at PRO-IMPA
Acknowledgements
USDA-ARS SPCLUSDA-ARS International
ProgramsPSU CAS Tag- Along ProgramPSU Plant Path. Travel AwardPSU Department of Plant
PathologyUSAID SANREM CRSP IPM CRSP
PSU Plant Path Paul Backman
USDA-ARS SPCL Bryan Bailey
Eric Rosenquist
INIAP Carmen Suarez
Danilo Vera
Karina Solis