peach yellows phytoplasma (peach yellows)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Means of Movement and Dispersal
- Plant Trade
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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IdentityTop of page
Preferred Scientific Name
- peach yellows phytoplasma
Preferred Common Name
- peach yellows
Other Scientific Names
- peach yellows MLO
- peach yellows mycoplasma-like organism
- peach yellows virus
International Common Names
- English: little peach
- PHYP29 (Peach yellows phytoplasma)
Taxonomic TreeTop of page
- Domain: Bacteria
- Phylum: Firmicutes
- Class: Mollicutes
- Order: Acholeplasmatales
- Family: Acholeplasmataceae
- Genus: Phytoplasma
- Species: peach yellows phytoplasma
Notes on Taxonomy and NomenclatureTop of page 'Phytoplasma' is a trivial name intended to become the generic name of the plant-pathogenic nonhelical mollicutes (mycoplasmas). Within the phytoplasmas, several pathogens or clusters of pathogens can be distinguished which have been or will be delineated as species under the provisional status 'Candidatus' (Seemüller et al., 1998). One of these clusters is the X-disease phytoplasma group. From DNA hybridization and rDNA sequence analysis it is evident that the peach yellows agent is closely related to, but distinct from, the western X-disease phytoplasma (Kirkpatrick et al., 1990; Kirkpatrick, 1995). However, detailed work on the genetic relationship of the peach yellows agent to other phytoplasmas (including the X-disease pathogen) remains to be done.
DescriptionTop of page Electron microscopical examinations of peach yellows-affected plants showed wall-less bacterial structures, typical for phytoplasmas, in phloem sieve tubes (Jones et al., 1974).
DistributionTop of page According to CABI/EPPO (1998), yellows diseases of peaches have been recorded in Israel, Lebanon, Syria and possibly Turkey. Yellows diseases, either described as peach yellows or European peach yellows, have also been reported from France (Cornaggia and Devignes, 1986), southern Italy (Nicotina et al., 1994) and Spain (Sanchez-Capuchino et al., 1976). All these reports are of uncertain validity, and probably refer to the recently characterized European stone fruit yellows phytoplasma (Lorenz et al., 1994; Seemüller and Foster, 1995). Molecular identification methods (Smart et al., 1996; Lee et al., 1998) will be required to confirm any previously supposed record of peach yellows phytoplasma in the EPPO region.
Peach yellows phytoplasma was first described near Philadelphia in Pennsylvania as early as 1791. It is now found in the Atlantic Coastal States, the Appalachian States, from Massachusetts to the Carolinas, Michigan, Illinois, Indiana, Kentucky and Tennessee. According to Pine and Gilmer (1976) and Kirkpatrick (1995), it is not established west of the Mississippi river nor in southern states. However, there is a recent report of peach yellows in Texas (Texas A&M University, 1997).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.Last updated: 23 Apr 2020
Risk of IntroductionTop of page Peach yellows phytoplasma is an EPPO A1 quarantine pest (OEPP/EPPO, 1986). In the EPPO region, peach, the main host, has the greatest economic importance of all species of Prunus. There are probably susceptible European cultivars and, in any case, American cultivars are frequently introduced. Though the American vector does not occur in Europe, local insects might act as vectors. The fact that the disease has from time to time been intercepted provides a reminder of the real risk of introduction. Healthy planting material of Prunus should evidently be free from peach yellows phytoplasma. However, this pest is really a historical curiosity rather than an immediate danger, and much less important in practice than peach X-disease phytoplasma (EPPO/CABI, 1997).
Hosts/Species AffectedTop of page Peach and nectarine (Prunus persica) are the principal hosts of peach yellows phytoplasma. Almonds (P. dulcis) and apricots (P. armeniaca) are also infected. All species of Prunus, including the economically important European plum (P. domestica), Japanese plum (P. salicina), myrobalan (P. cerasifera) and others, which have been experimentally graft-inoculated proved to be susceptible. Peach yellows phytoplasma is symptomless in some cultivars of P. salicina such as Abundance, Chalco and Chabot and in myrobalan rootstocks (Pine and Gilmer, 1976). The phytoplasma has also been experimentally transmitted to Catharanthus roseus (periwinkle) via dodder (Cuscuta sp.) bridges (Jones et al., 1974).
Host Plants and Other Plants AffectedTop of page
Growth StagesTop of page Flowering stage, Fruiting stage, Vegetative growing stage
SymptomsTop of page Leaf buds, even those that should normally remain dormant, develop prematurely. The leaves are yellowed and dwarfed, and the tree forms spindly branched shoots. In an advanced stage of disease, the shoot tips die back. Fruits mature several days to 3 weeks before healthy fruits and may be larger than normal. They are of poor quality, usually with a bitter taste. Severely affected trees die within 2-3 years but survival for 6 years or longer is possible (Pine and Gilmer, 1976; Kirkpatrick, 1995).
The disease caused by the little peach strain is slightly different. At the beginning of the growing season, the foliage is greener and proliferation of leaves on short side branches gives the tree a bushy appearance. The leaves become chlorotic during the season. The symptoms are first seen on one branch, or part of the tree, then spread to the whole tree. Fruits ripen up to 3 weeks later than healthy fruits and are small and insipid. The pits are small and the kernels either underdeveloped or fail to germinate (Pine and Gilmer, 1976).
List of Symptoms/SignsTop of page
|Fruit / abnormal patterns|
|Fruit / discoloration|
|Fruit / reduced size|
|Leaves / abnormal colours|
|Leaves / abnormal forms|
|Leaves / leaves rolled or folded|
|Leaves / yellowed or dead|
|Stems / dieback|
|Stems / witches broom|
|Whole plant / dwarfing|
|Whole plant / early senescence|
|Whole plant / plant dead; dieback|
Biology and EcologyTop of page The pathogen is restricted to phloem sieve tubes and is transmitted by a phloem-feeding leafhopper and grafting. Infection is persistent.
Means of Movement and DispersalTop of page The phytoplasma is transmitted by the leafhopper Macropsis trimaculata (Kunkel, 1933). It has an incubation period of 1-3 years in trees in the orchard, or less than 60 days in the glasshouse. In the vector, the mean incubation period is 16 days (Pine and Gilmer, 1976).
The capacity of the vector, Macropsis trimaculata, to disperse the phytoplasma is only local. The pathogen is most likely to be spread internationally in infected planting and propagation material or possibly in vectors carried on plants.
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Bark||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Flowers/Inflorescences/Cones/Calyx||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Fruits (inc. pods)||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Leaves||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Roots||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Seedlings/Micropropagated plants||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Stems (above ground)/Shoots/Trunks/Branches||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Plant parts not known to carry the pest in trade/transport|
|Growing medium accompanying plants|
ImpactTop of page Peach yellows was responsible for serious losses in the USA in the nineteenth century, when it was the object of classic research by Erwin Smith and of some of the first legislative measures against a plant disease (Michigan Yellows Law of 1875) (Ainsworth, 1981). Severe outbreaks continued into the early twentieth century, but the disease has now practically disappeared, largely because of effective control measures. Pine and Gilmer (1976) note that, in the past, peach yellows tended to follow a cyclical pattern in large peach-growing areas.
DiagnosisTop of page The disease can be indexed on an appropriate peach indicator such as seedling GF305 or cv. Elberta. Scion grafting and chipping should be preferred for budding. In the glasshouse, symptoms appear within 3 months from inoculation whereas in the field the test plants have to be observed for up to 4 years. An EPPO phytosanitary procedure for fruit tree phytoplasmas gives details (OEPP/EPPO, 1994).
A rapid method to detect phytoplasma infections is the DAPI (diamidino-2-phenylindole) fluorescence test. In this procedure, microtome sections are stained with DAPI and examined by epifluorescence microscopy (Seemüller, 1976).
More sensitive than biological tests and DAPI fluorescence microscopy is PCR. Template DNA is extracted from petioles, midribs or fruit peduncles tissue according to Ahrens and Seemüller (1992). Phloem scrapings, obtained as described by Ahrens and Seemüller (1994), is often a better source of sample DNA than leaf or root DNA. PCR is carried out using X-disease group-specific primer pair P1/WXint (Smart et al., 1996). For nested PCR assays, universal phytoplasma primers R16F2/R2 are used for initial amplification and X-disease group-specific primers R16(III)F2/R2 for reamplification reactions (Lee et al., 1994). Peach yellows-specific primers are not available, and methods to distinguish the peach yellows agent from other X-disease group members by rDNA RFLP analysis of the amplification products is untested.
Detection and InspectionTop of page Detection of peach yellows by visual inspection of shipped nursery plants and budwood is difficult.
Similarities to Other Species/ConditionsTop of page Symptomatically, peach yellows shows similarities to little peach disease and peach red suture. Based on symptom similarities and the fact that both pathogens are transmitted by the same leafhopper vector (Macropsis trimaculata), the agent of little peach disease is considered to be a strain of the peach yellows phytoplasma (Kunkel, 1933; Pine and Gilmer, 1976). In contrast, attempts to transmit peach red suture with this leafhopper have failed (Larsen and Waterworth, 1995). Information on the genetic relatedness of these three pathogens is missing.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.Infected trees should be destroyed and, if necessary, the vector Macropsis trimaculata should be controlled by insecticidal applications. Because Japanese plum (P. salicina) is susceptible to infection and is the preferred host of M. trimaculata, plum trees in the vicinity of peach orchards should be carefully monitored and removed if they test positive for the pathogen (Kirkpatrick, 1995). Healthy planting material should be used. In this respect, peach yellows was one of the first 'virus-like' diseases to be treated by thermotherapy - dormant trees treated for 10 minutes at 50°C and buds for 3-4 minutes at 50°C (Kunkel, 1936).
EPPO recommends (OEPP/EPPO, 1990) that Prunus planting material should come from a field inspected for disease during the growing season. Any vegetative material shipped from infested countries, should be subject to an official certification scheme, with particular emphasis on preventing re-infection of healthy material by airborne vectors. The EPPO certification scheme for fruit trees (OEPP/EPPO, 1992), though intended to be used primarily within the EPPO region, provides a suitable model.
ReferencesTop of page
Cornaggia D; Desvignes JC, 1986. Peach yellows. Study of the factors improving its detection in the greenhouse. Acta Horticulturae, 193:337-343.
EPPO, 1990. Specific quarantine requirements. EPPO Technical Documents, No. 1008. Paris, France: European and Mediterranean Plant Protection Organization.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Jones AL; Hooper GR; Rosenberger DA; Chevalier J, 1974. Mycoplasmalike bodies associated with peach and periwinkle exhibiting symptoms of peach yellows. Phytopathology, 64:1154-1156.
Kirkpatrick BC, 1995. Peach yellows. In: Ogawa JM, Zehr EI, Bird GW, Ritchie DF, Uriu K, Uyemoto JK, eds. Compendium of stone fruit diseases. St. Paul, MN, USA: American Phytopathological Society, 57.
Kirkpatrick BC; Fisher GA; Fraser JD; Purcell AH, 1990. Epidemiological and phylogenetic studies on western X-disease mycoplasma-like organisms. Recent advances in mycoplasmology. Proceedings of the 7th congress of the International Organization for Mycoplasmology, Baden near Vienna, 1988. [edited by Stanek, G.; Cassell, G.H.; Tully, J.G.; Whitcomb, R.F.] Stuttgart, Germany; Gustav Fischer Verlag, 288-297
Kunkel LO, 1933. Insect transmission of peach yellows. Contributions of the Boyce Thompson Institute, 1:19-28.
Kunkel LO, 1936. Heat treatment for the cure of peach yellows and other virus diseases of peach. Phytopathology, 26:809-830.
Larsen HJ; Waterworth HE, 1995. Peach red suture. In: Ogawa JM, Zehr EI, Bird GW, Ritchie DF, Uriu K, Uyemoto JK, eds. Compendium of stone fruit diseases. St. Paul, MN, USA: American Phytopathological Society, 55-56.
Lee IM; Gundersen DE; Hammond RW; Davis RE, 1994. Use of mycoplasmalike organism (MLO) group-specific oligonucleotide primers for nested-PCR assays to detect mixed-MLO infections in a single host plant. Phytopathology, 84(6):559-566
Lee IngMing; Gundersen-Rindal DE; Davis RE; Bartoszyk IM, 1998. Revised classification scheme of phytoplasmas based on RFLP analyses of 16S rRNA and ribosomal protein gene sequences. International Journal of Systematic Bacteriology, 48(4):1153-1169; 145 ref.
Lorenz KH; Dosba F; Poggi-Pollini C; Llacer G; Seemnller E, 1994. Phytoplasma diseases of Prunus species in Europe are caused by genetically similar organisms. Zeitschrift fur Pflanzenkrankheiten und Pflanzenschutz, 101(6):567-575
OEPP/EPPO, 1992. Certification schemes. Virus-free and virus-tested material of fruit trees and rootstocks. Bulletin OEPP/EPPO Bulletin, 21:267-278; 22:253-284.
OEPP/EPPO, 1994. MLOs in fruit trees and grapevine. Quarantine procedures No. 57. Bulletin OEPP/EPPO Bulletin, 24:339-342.
Pine TS; Gilmer RM, 1976. Peach yellows. In: Gilmer RM, Moore JD, Nyland G, Welsh MF, Pine TS, eds. Virus Diseases and Noninfectious Disorders of Stone Fruits in North America. USDA Agricultural Handbook No. 437. Washington, D.C.: United State Department of Agriculture, 91-95.
Sanchez-Capuchino JA; Llacer G; Casanova R; Forner JB; Bono R, 1976. Epidemiological studies on fruit tree mycoplasma diseases in the eastern region of Spain. Acta Horticulturae 67:129-131.
Schneider B; Seemüller E; Smart CD; Kirkpatrick BC, 1995. Phylogenetic classification of plant pathogenic mycoplasma-like organisms or phytoplasmas. In: Razin S, Tully JG, eds. Molecular and Diagnostic Procedures in Mycoplasmology, Vol. I. San Diego, CA, USA: Academic Press, 369-380.
Seemnller E; Foster JA, 1995. European stone fruit yellows. In: Ogawa JM, Zehr EI, Bird GW, Ritchie DF, Uriu K, Uyemoto JK, eds. Compendium of stone fruit diseases. St. Paul, MN, USA: American Phytopathological Society, 59-60.
Seemnller E; Marcone C; Lauer U; Ragozzino A; G÷schl M, 1998. Current status of molecular classification of the phytoplasmas. Journal of Plant Pathology, 80:3-26.
Seemüller E, 1976. Investigations to demonstrate mycoplasmalike organisms in diseased plants by fluorescence microscopy. Acta Horticulturae, 67:109-111.
Smart CD; Schneider B; Blomquist CL; Guerra LJ; Harrison NA; Ahrens U; Lorenz KH; Seemller E; Kirkpatrick BC, 1996. Phytoplasma-specific PCR primers based on sequences of the 16S-23S rRNA spacer region. Applied and Environmental Microbiology, 62(8):2988-2993; 33 ref.
Smith IM; McNamara DG; Scott PR; Holderness M, 1997. Quarantine pests for Europe. Second Edition. Data sheets on quarantine pests for the European Union and for the European and Mediterranean Plant Protection Organization. Quarantine pests for Europe. Second Edition. Data sheets on quarantine pests for the European Union and for the European and Mediterranean Plant Protection Organization., Ed. 2:vii + 1425 pp.; many ref.
Texas A&M University, 1997. Texas Plant Disease Handbook. World Wide Web page at http://cygnus.tamu.edu/texlab/tpdh.
CABI, Undated. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI
Pine TS, Gilmer RM, 1976. Peach yellows. In: Virus Diseases and Noninfectious Disorders of Stone Fruits in North America. USDA Agricultural Handbook No. 437, [ed. by Gilmer RM, Moore JD, Nyland G, Welsh MF, Pine TS]. Washington, D.C. United State Department of Agriculture. 91-95.
Distribution MapsTop of page
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