Widely distributed variation in tolerance to Phytophthora palmivora in four genetic groups of cacao

Andrew S. Fister, Mariela E. Leandro-Muñoz, Dapeng Zhang, James H. Marden, Peter Tiffin, Claude dePamphilis, Siela Maximova, Mark J. Guiltinan

Research output: Contribution to journalArticlepeer-review

Abstract

The tropical tree Theobroma cacao is the source of chocolate, and its seeds are a major export from many producing countries in Central and South America, Africa, and Asia. Every year, 30–40% of pre-harvest yield is lost due to disease damage. Host plant resistance is the most efficient and environmentally friendly approach for disease management. Historically, cacao germplasm resources have been underutilized in efforts to introduce novel sources of disease tolerance into breeding programs. Maintenance of cacao germplasm also relies on clonally propagated live collections, as cacao seeds do not exhibit dormancy and cannot be stored for more than a few weeks. In this study, we use a 90 SNP array to verify genetic identity of a set of clones in the International Cocoa Collection at CATIE, Costa Rica, and assign the clones into known genetic groups. We also used a detached leaf inoculation technique to measure the susceptibility of 60 genotypes to Phytophthora palmivora, a major cacao pathogen with global importance. We identified 24 genotypes with disease tolerance statistically similar to a standard tolerant variety (SCA6) and another 24 which performed similarly to a standard susceptible variety (ICS1). Our results indicate that each of the four included genetic groups show variability for quantitative resistance to P. palmivora. These results provide a foundation for future genomic and transcriptomic analysis of disease tolerance and susceptibility in the field at CATIE and provide guidelines for breeders searching for novel sources of tolerance that can be introduced into breeding programs.

Original languageEnglish (US)
Article number1
JournalTree Genetics and Genomes
Volume16
Issue number1
DOIs
StatePublished - Feb 1 2020

Bibliographical note

Funding Information:
Thank you to Lena Sheaffer and Melanie Perryman for assistance in project management and transportation of samples. Thank you to Wilbert Phillips-Mora for advice on the use of the IC3 collection. This work was supported by The Pennsylvania State University College of Agricultural Sciences, the Huck Institutes of the Life Sciences, the Penn State Endowed Program in Molecular Biology of Cacao, NSF Plant Genome Research Award 1546863 and by the USDA National Institute of Food and Agriculture, Federal Appropriations under Project PEN04569 and Accession number 1003147.

Funding Information:
Thank you to Lena Sheaffer and Melanie Perryman for assistance in project management and transportation of samples. Thank you to Wilbert Phillips-Mora for advice on the use of the IC3 collection.?This work was supported by The Pennsylvania State University College of Agricultural Sciences, the Huck Institutes of the Life Sciences, the Penn State Endowed Program in Molecular Biology of Cacao, NSF Plant Genome Research Award 1546863 and by the USDA National Institute of Food and Agriculture, Federal Appropriations under Project PEN04569 and Accession number 1003147.

Keywords

  • Genetics
  • Phytophthora
  • Resistance
  • Theobroma cacao

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