''Synchytrium'' is a large

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of plant pathogens within the phylum

Chytridiomycota Chytridiomycota are a division of zoosporic organisms in the kingdom Fungi, informally known as chytrids. The name is derived from the Ancient Greek ('), meaning "little pot", describing the structure containing unreleased zoöspores. Chytrids ...

. Species are commonly known as false rust or wart disease. Approximately 200

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

are described,Karling, J.S. 1964. ''Synchytrium''.Academic Press: New York. and all are obligate parasites of

angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

s, or

mosses Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and horn ...

.Sparrow FK. 1960. Aquatic Phycomycetes. The University of Michigan Press:Ann Arbor. 2nd edition Early species were mistakenly classified among the higher fungi (

Ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...

Basidiomycota 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, Basi ...

) because of their superficial similarity to the

rust fungi 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 ...

Anton de Bary Heinrich Anton de Bary (26 January 183119 January 1888) was a German surgeon, botanist, microbiologist, and mycologist (fungal systematics and physiology). He is considered a founding father of plant pathology (phytopathology) as well as the fou ...

and Mikhail S. Woronin recognized the true nature of these fungi and established the penus to accommodate ''Synchytrium taraxaci'', which grows on

dandelions ''Taraxacum'' () is a large genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus is native to Eurasia and Nor ...

, and ''S. succisae'', which grows on ''

Succisa pratensis ''Succisa pratensis'', also known as devil's-bit or devil's-bit scabious, is a flowering plant in the honeysuckle family Caprifoliaceae. It differs from other similar species in that it has four-lobed flowers, whereas small scabious and field s ...

''. ''Synchytrium taraxaci'' is the type of the genus. The genus has been divided into 6 subgenera based on differences in life cycles.

Morphology

Members of ''Synchytrium'' are endobiotic, holocarpic, and inoperculate. This means ''Synchytrium'' species grow inside of the host cell (endobiotic), produce structures other than a

zoosporangium A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or m ...

(holocarpic), and do not release

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or mo ...

s through a lid-like structure (inoperculate).Alexopoulos CJ, Mims CW, Blackwell M. 1996. Introductory Mycology. 4th edition.John Wiley & Sons, Inc. Zoospores of other members of

typically give rise to one zoosorangium or a polycentric thallus capable of producing many zoosporangia. In ''Synchytrium'', the zoospore nucleus divides many times with each daughter nucleus giving rise to a zoosporangium. This produces a cluster of clonal zoosporangia, often enveloped with a membrane. This cluster is called a sorus. The zoospore can give rise to the sorus directly or it can act as a prosorus. The difference is demonstrated in the life cycle, which is discussed below.

Life cycle

Most species share the same initial developmental stages. The released zoospores swim until they find a suitable host and will occasionally use amoeboid movement to better orient themselves to a host plant

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...

. After the zoospore attaches to a host cell, a narrow germ tube forms and penetrates the host cell, which is usually an

epidermal cell The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water relea ...

. An exception to this is ''S. minutum''; it uses the

stomata In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...

to enter the host plant and penetrate a sub-epidermal cell. After penetration, the zoospore

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...

flows into the host cell. The ''Synchytrium''

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucle ...

travels toward the host cell nucleus and becomes enveloped in host cytoplasm. After this point, differences arise among ''Synchytrium'' species. Species fall into one of two broad categories: short cycled and long cycled. Short cycled species follow one of two lines of development: sori, sporangia, zoospore or resting spore, sori, zoospore. Long cycled species follow a general pathway of prosori/sori, sporangia, zoospore,

resting spore A resting spore is a resistant cell, used to survive adverse environmental conditions. Resting spore is a term commonly applied to both diatoms and fungi. In fungi A resting spore can be a spore created by fungi which is thickly encysted (has a ...

, prosori/sori, sporangia, zoospore. The nuances in life cycles are used to delineate the subgenera.

Microsynchytrium

Species in this subgenus are long cycled and begin as a

uninucleate {{Short pages monitor