''Candidatus'' Phytoplasma pruni is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

phytoplasma Phytoplasmas are obligate intracellular parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission. Phytoplasmas were discovered in 1967 by Japanese scientists who termed them mycoplasma-li ...

in the

class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...

Mollicutes Mollicutes is a class of bacteria distinguished by the absence of a cell wall and its peptidoglycan. The word "Mollicutes" is derived from the Latin ' (meaning "soft" or "pliable"), and ' (meaning "skin"). Individuals are very small, typically on ...

, a class of

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

distinguished by the absence of a

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

pruni means "living on ''Prunus''", emphasizing the fact that the phytoplasma is a

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

of various ''

Prunus ''Prunus'' is a genus of flowering plant, flowering trees and shrubs from the family (biology), family Rosaceae. The genus includes plums, cherries, peaches, nectarines, apricots and almonds (collectively Drupe, stonefruit). The genus has a cosm ...

'' species, otherwise known as

stone fruit In botany, a drupe (or stone fruit) is a type of fruit in which an outer fleshy part (exocarp, or skin, and mesocarp, or flesh) surrounds a single shell (the ''pip'' (UK), ''pit'' (US), ''stone'', or ''pyrena'') of hardened endocarp with a seed ...

s. The phytoplasma is commonly called the X-disease phytoplasma. Like all phytoplasmas, ''Candidatus'' Phytoplasma pruni infects both plants and insects. Potential plant hosts include

peach The peach (''Prunus persica'') is a deciduous tree first domesticated and Agriculture, cultivated in China. It bears edible juicy fruits with various characteristics, most called peaches and the glossy-skinned, non-fuzzy varieties called necta ...

cherry A cherry is the fruit of many plants of the genus ''Prunus'', and is a fleshy drupe (stone fruit). Commercial cherries are obtained from cultivars of several species, such as the sweet '' Prunus avium'' and the sour '' Prunus cerasus''. The na ...

plum A plum is a fruit of some species in Prunus subg. Prunus, ''Prunus'' subg. ''Prunus'.'' Dried plums are often called prunes, though in the United States they may be labeled as 'dried plums', especially during the 21st century. Plums are ...

, and others. Known insect hosts include various species of

leafhopper Leafhopper is the common name for any species from the family (biology), family Cicadellidae: based on the type genus ''Cicadella''. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or ...

s. Since the

pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...

can not live outside of host cells, it must be transmitted to a new plant host by an infected leafhopper.

Taxonomy

The name Candidatus'' Phytoplasma pruni' was informally suggested by the International Research Program for Comparative Mycoplasmology in 2004, but the taxon was not formally described until 2013. It belongs to the X-disease group (16Sr group III), subgroup A (16SrIII-A), the most studied subgroup of 16SrIII. This subgroup of phytoplasma is associated with a number of diseases: PX11CT1^R is the reference strain for Candidatus'' Phytoplasma pruni'.

Related strains

Certain strains of phytoplasmas related to Candidatus'' Phytoplasma pruni' are associated with diseases of various plant species, including blueberry, clover, goldenrod, milkweed, spirea, pecan, poinsettia, potato, and walnut. These strains are classified in other subgroups of group III as follows:

A Candidatus'' Phytoplasma pruni'-related strain in subgroup 16SrIII-F has also been implicated as the cause of a greening disorder of ''Trillium grandiflorum'' and other ''Trillium'' species.

X-disease

X-disease was first discovered in California in 1931, where it was described as cherry buckskin. In 1933, the disease was found on peach in Connecticut, where it was called "X disease of peach" due to its unknown cause and mysterious nature. For many years, X-disease of peach was believed to be caused by a virus that was carried by insect vectors from nearby forests to peach orchards. In 1971, X-disease was found to be associated with mycoplasma-like organisms (now called phytoplasmas). X-disease is an infectious disease of stone fruits (''Prunus'' spp.). The disease is caused by ''Candidatus'' Phytoplasma pruni, a strain of phytoplasma belonging to 16Sr group III, the X-disease group of phytoplasmas.

Hosts

Historically, X-disease has been a major limiting factor in peach production in the United States. In addition to peach (''Prunus persica''), other species of the genus ''Prunus'' are susceptible to infection by the X-disease pathogen, including ''Prunus americana'' (wild American plum), ''Prunus armeniaca'' (apricot), ''Prunus avium'' (cherry), ''Prunus besseyi'' (Bessey cherry), ''Prunus cerasus'' (cherry), ''Prunus domestica'' (European plum), ''Prunus dulcis'' (almond), ''Prunus japonica'' (Chinese bush-cherry), ''Prunus munsoniana'' (wildgoose plum), ''Prunus persica'' var. ''nectarina'' (nectarine), ''Prunus salicina'' (Japanese plum), and ''Prunus virginiana'' (wild chokecherry).

Vectors

X-disease is transmitted by various species of leafhoppers in family Cicadellidae, including ''Colladonas clitellarius'', ''C. montanus'', ''C. geminatus'', ''Euscelidius variegatus'', ''Fieberiella florii'', ''Graphocephala confluens'', ''Gyponana lamina'', ''Keonella confluens'', ''Norvellina seminuda'', ''Osbornellus borealis'', ''Paraphlepsius irroratus'', and ''Scaphytopius delongi''.

Distribution

X-disease is present in North America (Canada, Costa Rica, United States) and South America (Argentina). It is localized in Canada (British Columbia, New Brunswick, Ontario) and widespread in the United States (California, Colorado, Connecticut, Massachusetts, Michigan, Missouri, Nebraska, New York, North Dakota, Oregon, Pennsylvania, Utah, Virginia, Washington). The disease may also be present in Asia (India, Japan), Europe (Poland), and additional U.S. states.

References

{{Taxonbar, from= Q63348866 Mollicutes Bacterial tree pathogens and diseases Bacterial plant pathogens and diseases Ornamental plant pathogens and diseases Candidatus taxa