Rachel Melnick Anissa poleatewich Department of Plant pathology Penn State university

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Rachel MelnickAnissa poleatewichDepartment of
Plant pathologyPenn State university
Field evaluation of endophytes for management of
Witches broom on cacao
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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

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Growth chamber studies

• Plants maintained in growth chambers
• Detached leaf assays used to screen isolates
• Colonized leaves challenged with pathogen

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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

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Experimental System
Disease Challenge
TIME
Bacterial Application
Colonization
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Ecuador field trials
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Disease challenge in Ecuador
Susceptible tree full of witches broom
Spores raining from infected trees onto seedlings
Seedlings undergoing disease screening
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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

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Disease severity

• One bacterial treatment has completely suppressed
  disease....as of March 2008

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Disease severity

• Tolerant genotypes have significantly less
  disease than susceptible genotypes

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Coupling tolerant genotypes with bacteria can
reduce disease
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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

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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

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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

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Acknowledgements

• PSU Plant Path
• Paul Backman
• USDA-ARS SPCL
• Bryan Bailey
• Eric Rosenquist
• INIAP
• Carmen Suarez
• Danilo Vera
• Karina Solis

USDA-ARS SPCL USDA-ARS International Programs PSU
CAS Tag- Along Program PSU Plant Path. Travel
Award PSU Department of Plant Pathology USAID
SANREM CRSP IPM CRSP