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