Studies on secondary metabolites associated with witches' broom disease, floral biology, and seed fermentation in cacao

Theobroma cacao L., a tree native to the Amazon, is cultivated in the tropics throughout the world for its seeds, used primarily for chocolate production. Cacao production is limited by several problems. Cocoa pod borer, an insect that burrows through pods, damages seeds, allowing contamination by toxigenic fungal species. Many fungal diseases infect cacao. Among them, Moniliophthora perniciosa, the causal agentof witches' broom disease, severely affects plantations throughout South America and the Caribbean. Cacao yields are further limited by the naturally low rates of fruit set. Moreover, disease tolerant varieties are usually self-incompatible low producers and do not give a superior chocolate flavor compared to some disease susceptible and selfcompatible genotypes with highly valued aroma compounds. During this project, problems associated with three main aspects of cacao were investigated: disease, production and processing. Studies on plant-endophyte-pathogen interactions allowed for the identification of new possible mechanisms of disease control; studies on cacao flower physiology indicated ways to improve pollination and therefore increase fruit set and crop yield; and investigations of the fermentation step of cacao processing permitted discovery of a method for maintaining higher levels of compounds valued by cacao manufacturers. Flavan-3-ol monomers and oligomers, purine alkaloids and salicylic acid, volatile organic compounds, polyketides and other phenolic compounds were among the determined bioactive compounds found in cacao, pathogens and endophytes, with influence on disease, production, and processing.Ph.D.Includes bibliographical references (p. 210-225)