Frosty pod rot (moniliophthora roreri)

Abstract

The history of frosty pod rot is chronologed and divided conveniently into periods or eras to better reflect the state of knowledge of the disease at the time. During the first period (1917–1975), the causal agent was ascribed to a species of Monilia (Ascomycota), but knowledge of the life cycle-including the mechanics of dispersal and infection-was wanting. In the second period (1975–1987), details of the life cycle emerged which cast doubts on the phylogeny of the fungus: specifically, as a sophisticated hemibiotroph with two genetically and morphologically distinct nutritional phases-parasitic, monokaryotic; saprophytic, dikaryotic. This led to a critical examination of its morphology which showed that the fungus has a unique form of sporogenesis and a hyphal structure characteristic of the Basidiomycota. The new genus Moniliophthora was erected to accommodate this species, considered to be the asexual morph of an unknown basidiomycete. In the present molecular period, DNA sequencing has revealed that the pathogen is a sister species of the witches’ broom fungus (see Chap.​ 5) and both pertain to a unique clade within the Marasmiaceae. In addition, cytological evidence indicates that the purported conidia (mitospores) have a sexual function since meiotic events have been documented. The biology and evolution of the fungus is discussed, with particular reference to another variety occurring on wild Theobroma hosts in the forests of western Ecuador and Colombia. Finally, past and present disease management strategies are reviewed.