Guest, D. 2007. Black pod: Diverse pathogens with a global impact on cocoa yield. Phytopathology 97:1650-1653. Pathogens of the Straminipile genus Phytophthora cause significant disease losses to global cocoa production. P. megakarya causes significant pod rot and losses due to canker in West Africa, whereas P. capsici and P. citrophthora cause pod rots in Central and South America. The global and highly damaging P. palmivora attacks all parts of the cocoa tree at all stages of the growing cycle. This pathogen causes 20 to 30% pod losses through black pod rot, and kills up to 10% of trees annually through stem cankers. P. palmivora has a complex disease cycle involving several sources of primary inoculum and several modes of dissemination of secondary inoculum. This results in explosive epidemics during favorable environmental conditions. The spread of regional pathogens must be prevented by effective quarantine barriers. Resistance to all these Phytophthora species is typically low in commercial cocoa genotypes. Disease losses can be reduced through integrated management practices that include pruning and shade management, leaf mulching, regular and complete harvesting, sanitation and pod case disposal, appropriate fertilizer application and targeted fungicide use. Packaging these options to improve uptake by smallholders presents a major challenge for the industry.

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Cacao Diseases: Important Threats to Chocolate Production Worldwide Black Pod: Diverse Pathogens with a Global Impact on Cocoa Yield

Leaf inoculation as an early screening test for cocoa (Theobroma cacao L.) resistance to Phytophthora black pod disease.

Traditional fermentations of the local Ecuadorian cocoa type Nacional, with its fine flavor, are carried out in boxes and on platforms for a short time A multiphasic approach, encompassing culture-dependent and -independent microbiological analyses of fermenting cocoa pulp-bean samples, metabolite target analyses of both cocoa pulp and beans, and sensory analysis of chocolates produced from the respective fermented dry beans, was applied for the investigation of the influence of these fermentation practices on the yeast and bacterial species diversity and community dynamics during cocoa bean fermentation A wide microbial species diversity was found during the first 3 days of all fermentations carried out The prevailing ethanol-producing yeast species were Pichia kudriavzevii and Pichia manshurica, followed by Saccharomyces cerevisiae Leuconostoc pseudomesenteroides (glucose and fructose fermenting), Fructobacillus tropaeoli-like (fructose fermenting), and Lactobacillus fermentum (citrate converting, mannitol producing) represented the main lactic acid bacterial species in the fermentations studied, resulting in intensive heterolactate metabolism of the pulp substrates Tatumella saanichensis and Tatumella punctata were among the members of the family Enterobacteriaceae present during the initial phase of the cocoa bean fermentations and could be responsible for the production of gluconic acid in some cases Also, a potential new yeast species was isolated, namely, Candida sorbosivorans-like Acetic acid bacteria, whose main representative was Acetobacter pasteurianus, generally appeared later during fermentation and oxidized ethanol to acetic acid However, acetic acid bacteria were not always present during the main course of the platform fermentations All of the data taken together indicated that short box and platform fermentation methods caused incomplete fermentation, which had a serious impact on the quality of the fermented dry cocoa beans

Species Diversity, Community Dynamics, and Metabolite Kinetics of the Microbiota Associated with Traditional Ecuadorian Spontaneous Cocoa Bean Fermentations

A linkage map of cacao based on codominant markers has been constructed by integrating 201 new simple sequence repeats (SSR) developed in this study with a number of isoenzymes, restriction fragment length polymorphisms (RFLP), microsatellite markers and resis- tance and defence gene analogs (Rgenes-RFLP) previ- ously mapped in cacao. A genomic library enriched for (GA)n and (CA)n was constructed, and 201 new mi- crosatellite loci were mapped on 135 individuals from the same mapping population used to establish the first reference maps. This progeny resulted from a cross between two heterozygous cacao clones: an Upper-Ama- zon Forastero (UPA 402) and a Trinitario (UF 676). The new map contains 465 markers (268 SSRs, 176 RFLPs, five isoenzymes and 16 Rgenes-RFLP) arranged in ten linkage groups corresponding to the haploid chromosome number of cacao. Its length is 782.8 cM, with an average interval distance between markers of 1.7 cM. The new microsatellite markers were distributed throughout all linkage groups of the map, but their distribution was not random. The length of the map established with only SSRs was 769.6 cM, representing 94.8% of the total map. The current level of genome coverage is approximately one microsatellite every 3 cM. This new reference map provides a set of useful markers that is transferable across different mapping populations and will allow the identi- fication and comparison of the most important regions involved in the variation of the traits of interest and the development of marker-assisted selection strategies.

A new cacao linkage map based on codominant markers: development and integration of 201 new microsatellite markers

Pathogens of the Straminipile genus Phytophthora cause significant disease losses to global cocoa production. P. megakarya causes significant pod rot and losses due to canker in West Afric...

https://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO-97-12-1650

Black pod: diverse pathogens with a global impact on cocoa yield.

Phytophthora palmivora causes pod rot, a serious disease on cocoa widespread throughout the producing regions. In order to ascertain the genetic determination of cocoa resistance to P. palmivora, a...

Genetic mapping of resistance factors to Phytophthora palmivora in cocoa.

Cocoa pod rot, caused by different Phytophthora species, is rife in all production zones. Phytophthora spp. control is therefore a major challenge for world cocoa cultivation, and selection of resistant material is a priority research theme for many producing countries. Various genetic trials have been set up over many years in zones affected by the disease. In Cameroon, a 6x6 diallel mating design was set up to study heritability of the resistance trait. Field observations led to the classification of parents according to their ability to transmit resistance to their progenies. These field measurements were long and laborious, so a resistance test based on artificial leaf inoculations was developed. This article studies the correspondence between results obtained with the test and observations of rot rates in the field. There was a significant genetic correlation between pod rot rate in the field and leaf test data, so using this resistance test could shorten cocoa tree selection cycles.

Validity of a leaf inoculation test to assess the resistance to Phytophthora megakarya in a cocoa (Theobroma cacao L.) diallel mating design

Diversity of Phytophthora megakarya in Central and West Africa revealed by isozyme and RAPD markers

https://www.worldcocoafoundation.org/wp-content/uploads/files_mf/nyasse2007.pdf

Integrated management of Phytophthora diseases on cocoa (Theobroma cacao L): Impact of plant breeding on pod rot incidence

La pourriture des cabosses de cacaoyer est responsable de pres de 30% des pertes de la production mondiale de cacao. Cette maladie est due a diverses especes du genre Phytophthora. L'espece la plus dommageable, P. megakarya, envahit actuellement la Cote d'Ivoire, premier pays producteur. Face a cette menace, un projet de recherche sur les bases genetiques de la resistance des cacaoyers aux maladies a Phytophthora a reuni des equipes de chercheurs du Cirad, en France, de l'irad, au Cameroun, du Cnra, en Cote d'Ivoire et du Cru, a Trinidad. Ces recherches ont recu l'appui financier des chocolatiers europeens a travers l'association Caobisco. Cet ouvrage de synthese presente les resultats acquis lors des travaux conduits dans le cadre du projet. Il a pour principal objectif de mettre a la disposition de la communaute internationale les connaissances et les outils utilisables pour la selection de cacaoyers plus resistants a Phytophthora. Improvement of cocoa tree resistance to Phytophthora diseases fait le point sur la diversite du pathogene, les connaissances epidemiologiques, les parametres genetiques de la resistance observee en champ, les aspects pratiques de la selection. La pertinence de differents tests d'evaluation a partir d'inoculations artificielles et l'utilisation des marqueurs moleculaires dans la selection de materiel resistant sont largement abordees. (Resume d'auteur)

Denis Despréaux

Papers

Genetic mapping of resistance factors to Phytophthora palmivora in cocoa.

Validity of a leaf inoculation test to assess the resistance to Phytophthora megakarya in a cocoa (Theobroma cacao L.) diallel mating design

Diversity of Phytophthora megakarya in Central and West Africa revealed by isozyme and RAPD markers

Integrated management of Phytophthora diseases on cocoa (Theobroma cacao L): Impact of plant breeding on pod rot incidence

Improvement of cocoa tree resistance to Phytophthora diseases