''Hemileia vastatrix'' is a multicellular

basidiomycete Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Bas ...

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 ...

of the order

Pucciniales Rusts are plant diseases caused by pathogenic fungi of the order Pucciniales (previously known as Uredinales). An estimated 168 rust genera and approximately 7,000 species, more than half of which belong to the genus ''Puccinia'', are currently a ...

(previously also known as Uredinales) that causes coffee leaf rust (CLR), a disease affecting the

coffee plant ''Coffea'' is a genus of flowering plants in the family Rubiaceae. ''Coffea'' species are shrubs or small trees native to tropical and southern Africa and tropical Asia. The seeds of some species, called coffee beans, are used to flavor variou ...

. Coffee serves as the obligate host of coffee rust, that is, the rust must have access to and come into physical contact with coffee (''

Coffea ''Coffea'' is a genus of flowering plants in the family Rubiaceae. ''Coffea'' species are shrubs or small trees native to tropical and southern Africa and tropical Asia. The seeds of some species, called coffee beans, are used to flavor vario ...

sp.'') in order to survive. CLR is one of the most economically important diseases of coffee, worldwide. Previous epidemics have destroyed coffee production of entire countries. In more recent history, an epidemic in Central America in 2012 reduced the region's coffee output by 16%. The primary pathological mechanism of the fungus is a reduction in the plant's ability to derive energy through photosynthesis by covering the leafs with fungus spores and/or causing leaves to drop from the plant. The reduction in photosynthetic ability (plant's metabolism) results in a reduction in quantity and quality of flower and fruit production, which ultimately reduces the beverage quality.

Appearance

The

mycelium Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates ...

with

uredinia {{Short pages monitor