''Candidatus'' Phytoplasma pruni is a species of phytoplasma in the class Mollicutes, a class of bacteria distinguished by the absence of a

cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...

. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

pruni means "living on ''Prunus''", emphasizing the fact that the phytoplasma is a parasite of various '' Prunus'' species, otherwise known as stone fruits. 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,

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 nam ...

plum A plum is a fruit of some species in ''Prunus'' subg. ''Prunus'.'' Dried plums are called prunes. History Plums may have been one of the first fruits domesticated by humans. Three of the most abundantly cultivated species are not found i ...

, and others. Known insect hosts include various species of

leafhopper A leafhopper is the common name for any species from the family Cicadellidae. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or trees. Their hind legs are modified for jumping, and a ...

s. Since the pathogen 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

External links

* Mollicutes Bacterial tree pathogens and diseases Bacterial plant pathogens and diseases Ornamental plant pathogens and diseases Candidatus taxa {{plant-disease-stub