Field evaluation of endophytes for management of Witches’ broom on cacao Rachel Melnick Anissa poleatewich Department of Plant pathology Penn State university 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 Experimental System Disease Challenge TIME Bacterial Application Colonization

Ecuador field trials Colonizing experiment

Disease challenge in Ecuador Susceptible tree full of witches’ broom Spores raining from infected trees onto seedlings Seedlings undergoing disease screening

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

Disease severity Tolerant genotypes have significantly less disease than susceptible genotypes A2634 statistically significantly reduced disease. A2634 & A2126 are nacional cocoa and tolerant. EET19 susceptible control. CCN51 widely planted genotypes due to high yield, but did no SIGNIFICANT disease reduction

Coupling tolerant genotypes with bacteria can reduce disease

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 ARISA – automatic ribosomal intergenic spacer analysis qPCR – Quantitative PCR. Real time PCR used to quantify mRNA to determine the expression leaves of genes in the plant

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 PSU Plant Path USDA-ARS SPCL 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