''Moniliophthora perniciosa'' (previously ''Crinipellis perniciosa'') is a
fungus
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...
that causes "
witches' broom disease" (WBD) of the cocoa tree
''T. cacao''.
This pathogen is currently limited to South America, Panama and the Caribbean, and is perhaps one of the best-known cocoa diseases, thought to have co-evolved with cocoa in its centre of origin (first recorded in the Brazilian
Amazon
Amazon most often refers to:
* Amazons, a tribe of female warriors in Greek mythology
* Amazon rainforest, a rainforest covering most of the Amazon basin
* Amazon River, in South America
* Amazon (company), an American multinational technolog ...
in 1785).
This fungus is
hemibiotroph Hemibiotrophs are the spectrum of plant pathogens, including bacteria, oomycete and a group of plant pathogenic fungi that keep its host alive while establishing itself within the host tissue, taking up the nutrients with brief biotrophic-like pha ...
, with two characteristic phases: biotrophic (expanding and infecting, on living tissue) and saprotrophic (producing
basidiospore
A basidiospore is a reproductive spore produced by Basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are ...
s, on necrotic tissue). The biotrophic stage, and what triggers its switch to a saprotrophic stage, are still not understood.
Hosts and symptoms
''Moniliophthora perniciosa'' can infect a number of hosts. Generally, ''M. perniciosa'' infects tropical host plants, and host plants in the Upper Amazon River basin on the eastern side of the Andes.
''M. perniciosa'' is now known to comprise four different biotypes (C, S, L and H), each infecting different (and unrelated) host plants. The economically important C-biotype infects species of ''Theobroma'' and ''Herrania'' (family
Malvaceae
Malvaceae, or the mallows, is a family of flowering plants estimated to contain 244 genera with 4225 known species. Well-known members of economic importance include okra, cotton, cacao and durian. There are also some genera containing familia ...
).
A second biotype (L-biotype) was found on liana vines in Ecuador; subsequently the host was identified as ''Arrabidaea verrucosa'' (
Bignoniaceae
Bignoniaceae is a family of flowering plants in the order Lamiales commonly known as the bignonias or trumpetvines.Vernon H. Heywood, Richard K. Brummitt, Ole Seberg, and Alastair Culham. ''Flowering Plant Families of the World''. Firefly Book ...
) but witches' broom symptoms have not been observed on this host.
The S-biotype, reported only from Brazil caused witches' broom symptoms on hosts within the family
Solanaceae
The Solanaceae , or nightshades, are a family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spices, weeds, and or ...
, including ''Solanum rugosum''; . Under experimental conditions, this biotype is also able to cause witches' broom symptoms on tomato, aubergine, potato, pepper and potato. Most recently discovered is the H-biotype, which infects ''
Heteropterys
''Heteropterys'' is a genus in the Malpighiaceae, a family (biology), family of about 75 genera of flowering plants in the order Malpighiales. ''Heteropterys'' comprises over 140 species of woody vines, shrubs, and small trees found in the New Wo ...
acutifolia'' (
Malpighiaceae
Malpighiaceae is a family of flowering plants in the order Malpighiales. It comprises about 73 genera and 1315 species, all of which are native to the tropics and subtropics. About 80% of the genera and 90% of the species occur in the New Wor ...
) but this has been reclassified as a separate species, ''Moniliophthora brasiliensis''. Recent phylogenetic analysis of field-collected basidiomes and cultures suggests that other biotypes may also exist.
Investigation of the breeding biology of these various biotypes found that those causing disease symptoms (C,S) are non-outcrossing (primary
homothallic), wherein a single