Athelia rolfsii is a corticioid fungus

Corticioid fungi

The corticioid fungi are a group of fungi in the Basidiomycota typically having effused, smooth basidiocarps that are formed on the undersides of dead attached or fallen branches. They are sometimes colloquially called crust fungi or patch fungi...

 in the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Atheliaceae

Atheliaceae

The Atheliaceae are a family of fungi in the monotypic order Atheliales. Both the order and the family were described by W. Jülich in 1981. According to a 2008 estimate, the family contains 22 genera and 106 species.-Genera:*Amphinema...

. It is a facultative

Facultative

Facultative means "optional" or "discretionary" , used mainly in biology in phrases such as:* Facultative anaerobe, an organism that can use oxygen but also has anaerobic methods of energy production...

 plant pathogen and is the causal agent of "southern blight" disease in crops.

Taxonomy

The species was first described in 1911 by Italian mycologist Pier Andrea Saccardo

Pier Andrea Saccardo

Pier Andrea Saccardo was an Italian botanist and mycologist.- Life :...

, based on specimens sent to him by Peter Henry Rolfs

Peter Henry Rolfs

Peter Henry Rolfs was a prominent Florida agronomist in the early twentieth century. He directed the Florida Agriculture Experiment Station from 1905 to 1920, and from 1915 to 1920 served as the Dean of the College of Agriculture at the University of Florida...

 who considered the unnamed fungus to be the cause of tomato

Tomato

The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...

 blight

Blight

Blight refers to a specific symptom affecting plants in response to infection by a pathogenic organism. It is simply a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. Accordingly, many diseases that primarily exhibit this...

 in Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

. The specimens sent to Saccardo were sterile, consisting of hyphae and sclerotia. He placed the species in the old form genus Sclerotium

Typhula

Typhula is a genus of clavarioid fungi in the order Agaricales. Species of Typhula are saprotrophic, mostly decomposing leaves, twigs, and herbaceous material. Basidiocarps are club-shaped or narrowly cylindrical and are simple , often arising from sclerotia. The anamorphic genus Sclerotium is a...

, naming it Sclerotium rolfsii. It is, however, not a species of Sclerotium in the strict sense.

In 1932, Mario Curzi discovered that the teleomorph (spore-bearing state) was a corticioid fungus

Corticioid fungi

The corticioid fungi are a group of fungi in the Basidiomycota typically having effused, smooth basidiocarps that are formed on the undersides of dead attached or fallen branches. They are sometimes colloquially called crust fungi or patch fungi...

 and accordingly placed the species in the form genus Corticium

Corticium

Corticium is a genus of crust fungi in the family Corticiaceae. According to a 2008 estimate, the genus contains 25 widely distributed species.-Species:*Corticium appalachiense*Corticium auberianum*Corticium boreoroseum...

. With a move to a more natural classification of fungi, Corticium rolfsii was transferred to Athelia

Athelia (fungus)

Athelia is a genus of corticioid fungi in the family Amylocorticiaceae. Some species are facultative parasites of plants and of lichens. The widespread genus contains 28 species....

in 1978.

Description

The fungus produces effused basidiocarps (fruit bodies) that are smooth and white. Microscopically, they consist of ribbon-like hyphae with clamp connection

Clamp connection

A clamp connection is a structure formed by growing hyphal cells of certain fungi. It is created to ensure each septum, or segment of hypha separated by crossed walls, receives a set of differing nuclei, which are obtained through mating of hyphae of differing sexual types...

s. Basidia are club-shaped, bearing four smooth, ellipsoid basidiospores, measuring 4-7 by 3-5 μm. Small, brownish sclerotia (hyphal propagules) are also formed, arising from the hyphae.

Southern Blight

Athelia rolfsii occurs in soil as a saprotroph, but can also attack living plants. It has an almost indiscriminate host range, but its capacity to form sclerotia (propagules that remain in the soil) means that it particularly attacks seasonal crops. It mostly occurs in warm soils (above 15°C) and can be a serious pest of vegetables in tropical and subtropical regions (including Florida, where it was first recognized), causing "southern blight".

External links

• Index Fungorum
• "Kudzu of the Fungal World" at NC State University