Genomics, transcriptomics, and beyond: The fifteen years of cacao’s witches’ broom disease genome project

Abstract

Cacao production in Brazil was severely affected by the outbreak of witches’ broom disease (WBD) in the late 1980s. WBD is caused by the basidiomycete fungus Moniliophthora perniciosa, a hemibiotrophic pathogen that displays an uncommonly long-lasting biotrophic stage during which the host cacao suffers intense morphologic alterations in the infected shoots, giving rise to “green brooms.” Two months after infection, the fungus becomes necrotrophic resulting in the necrosis and destruction of the infected tissues that turn into a “dry broom.” During the last 15 years, the knowledge of this devastating and intriguing disease has been growing due to initiatives such as the WBD genome project. By using genomics and transcriptomics as tools to obtain insights about this disease, the WBD project has been elucidating the biochemistry and physiology of both plant host and pathogen, paving the way for practical applications to combat the fungus. In this chapter we present an overview of progress in the understanding of M. perniciosa genetics and the molecular mechanisms governing WBD, provide a model for the M. perniciosa–cacao interaction, and point to new directions to fight this disease.