candidatus phytoplasma pruni candidatus phytoplasma pruni candidatus phytoplasma pruni is a species of phytoplasma in the class mollicutes, a class of bacteria distinguished by the absence of a cell wall. the specific epithet 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. candidatus phytoplasma pruni scientific classification domain: bacteria phylum: mycoplasmatota class: mollicutes order: acholeplasmatales family: acholeplasmataceae genus: candidatus phytoplasma species: ca. p. pruni binomial name candidatus phytoplasma prunidavis et al. 2013 synonyms peach western x phytoplasmapeach x disease phytoplasmapeach yellow leafroll phytoplasmawestern x disease phytoplasma like all phytoplasmas, candidatus phytoplasma pruni infects both plants and insects. potential plant hosts include peach, cherry, plum, and others. known insect hosts include various species of leafhoppers. 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: 'candidatus phytoplasma pruni' strain(s) associated disease 16sr group-subgroup px11ct1r, px11ct2, px92ct1, px92ct2, px92ct3, px92ct4, cx-95, wx95 peach x-disease 16sriii-a pr peach rosette 16sriii-a lp little peach 16sriii-a prs peach red suture 16sriii-a px11ct1r 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: 'candidatus phytoplasma pruni'-related strains strain associated disease 16sr group-subgroup cye (cye-c) clover yellow edge 16sriii-b pbt (pb) pecan bunchy top 16sriii-c gr1 goldenrod yellows 16sriii-d sp1 spirea stunt 16sriii-e mw1 milkweed yellows 16sriii-f vac (vacwb) vaccinium witches' broom 16sriii-f akpot7 potato purple top 16sriii-f wwb walnut witches' broom 16sriii-g poibi poinsettia branch inducing 16sriii-h vgyiii virginia grapevine yellows 16sriii-i 'candidatus phytoplasma pruni'-related strains strain associated disease 16sr group-subgroup chwbiii chayote witches' broom 16sriii-j slf strawberry leafy fruit 16sriii-k cfsd cassava frog skin disease 16sriii-l mt117 potato purple top 16sriii-m akpot6 potato purple top 16sriii-n danv dandelion virescence 16sriii-p brwb7 black raspberry witches' broom 16sriii-q chd sweet and sour cherry 16sriii-t cwl cirsium white leaf 16sriii-u passwb-br4 passion fruit witches' broom 16sriii-v 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-diseasecausal agentscandidatus phytoplasma prunihostsvarious prunus speciesvectorsvarious species of leafhoppers in family cicadellidaeeppo codephyppndistributionnorth america (canada, costa rica, united states) and south america (argentina) 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.