Phytoplasma pyri
(pear decline)

Pictures

Top of page

Identity

Top of page

Preferred Scientific Name

• Phytoplasma pyri Seemüller & Schneider, 2004

Preferred Common Name

• pear decline

Other Scientific Names

• Candidatus Phytoplasma pyri Seemüller & Schneider, 2004
• pear decline phytoplasma Seemüller et al., 1994

International Common Names

• English: Parry's disease; peach yellow leaf roll; pear leaf curl; pear moria
• Spanish: decaimiento del peral

Local Common Names

• Croatia: ugibanje kruske
• Czechoslovakia (former): chradnuti hrusne
• France: dépérissement du poirier; flétrissement du poirier
• Germany: Birnenverfal
• Greece: parakmi achladias
• Hungary: kortepusztulas
• Italy: moria del pero
• Spain: decaimento del peral

English acronym

• PD

EPPO code

• PHYPPY (Phytoplasma pyri)

Taxonomic Tree

Top of page

• Domain: Bacteria
•     Phylum: Firmicutes
•         Class: Mollicutes
•             Order: Acholeplasmatales
•                 Family: Acholeplasmataceae
•                     Genus: Phytoplasma
•                         Species: Phytoplasma pyri

Notes on Taxonomy and Nomenclature

Top of page Pear decline is a disease constantly associated with the presence of phytoplasmas in the sieve tubes of diseased pear trees (Hibino and Schneider, 1970; Seemüller, 1976).

Phytoplasmas, formerly known as mycoplasma like organisms (=MLOs), are unusual, self-replicating bacteria, possessing very small genomes, lacking cell wall components and displaying genetic economy that requires a strict dependence on the host for nutrients and refuge. They are transmitted from diseased to healthy plants by phloem-feeding vectors such as leafhoppers or planthoppers. They are evolutionary descendants from the low G+C-containing, Gram-positive bacteria, and through chromosome reduction, represent the smallest self-replicating life forms. These prokaryotes belong to a monophyletic clade of organisms related to Mollicutes (ICSB, 1993, 1997). Their closest relatives are the genus Acholeplasma and Anaeroplasma (Davis et al., 1997; Weisburg et al., 1989). These relationships have been clearly stated by sequence analysis of conserved genes (Lim and Sears, 1992; Gundersen et al., 1994).

While the culturable Mollicutes are differentiated and classified on the basis of phenotypic and genotypic characteristics (ICSB, 1995), the phytoplasmas are characterized by serology and, mainly, by dot and Southern blot analyses, RFLP of PCR-amplified conserved DNA, and sequence analysis of conserved DNA (ICSB, 1993, 1997).

Twenty major groups of phytoplasmas have been distinguished (Seemüller et al., 1998). The apple proliferation group phytoplasmas have been reported only in Europe (as determined phytoplasmas) with the exception of the peach yellow leaf roll agent, which also occurs in the USA. The pear decline phytoplasma is one of the three phytoplasmas belonging to the apple proliferation group (=clade). The peach yellow leaf roll and pear decline phytoplasmas are closely related (Kirkpatrick et al., 1994; Kison et al., 1994).

Further information on the molecular classification of phytoplasmas belonging to the apple proliferation clade may be found in Seemüller et al. (1998).

In 2004 it was proposed to accommodate phytoplasmas within the novel genus 'Candidatus (Ca.) Phytoplasma', and pear decline as the species Candidatus Phytoplasma pyri (Seemüller and Schneider, 2004).

Distribution

Top of page Records from Austria, Belgium, Greece, Romania, Switzerland, former USSR (Németh, 1986), India and South Africa (Seemüller, 1990) are based on symptoms and may require further confirmation.

See also CABI/EPPO (1998, No. 269).

Distribution Table

Top 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

Hosts/Species Affected

Top of page Pear is the main host of pear decline phytoplasma. Pear cultivars known to be affected include:

Highly susceptible: Hardy Burré, Magness, Precocious and Williams (Németh, 1986); Max Red Barlett (Anon., 1997); Conference (Davies et al., 1992); Abate Fetel and Kaiser (Giunchedi et al., 1995).

Medium susceptibility: Comice, Concorde (Davies et al., 1992); Montecosa Precoz (Anon., 1997)

The phytoplasma can be graft transmitted to Pyronia veitchii, Pyrus amygdaliformis lobata, P. aromatica, P. betulifolia, P. calleriana, P. ussuriensis (Németh, 1986) and to Catharanthus roseus by dodder bridge and insect vector.

Host Plants and Other Plants Affected

Top of page

Growth Stages

Top of page Flowering stage, Fruiting stage, Vegetative growing stage

Symptoms

Top of page Symptomatology differs depending on the cultivars and rootstocks variety. In particular, the grade of resistance of rootstocks may explain the occurrence of slow and quick decline (Seemüller et al., 1986; Giunchedi et al., 1995, Pastore et al., 1997). Generally the first symptom is seen in autumn when the leaves of affected trees develop a premature red colour followed by early leaf fall. The second symptom is seen in the following spring when leaves remain small and pale, there being little or no shoot growth and no fruit production. Often, a necrotic line is visible in the inner part of the bark at the stock-scion union. The severity of the spring symptoms can vary from death or severe stunting to their complete absence. Westwood and Cameron (1978) suggested that if disease trees are not exposed to repeated infestations of psyllids the symptoms became milder after some dormant seasons. The disease needed repeated infection by the vectors especially in trees grafted on quince rootstocks.

A typical diagnostic symptom of pear decline is a dark phloem ring immediately below the graft union in bark sections from infected trees, visible by microscopic examination of stained transverse sections.

List of Symptoms/Signs

Top of page

Biology and Ecology

Top of page Pear decline can be transmitted by grafting, budding and chip budding. It is not perpetuated by the standard propagation practices when quince rootstocks are used even though several quince rootstocks selections showed a considerable variation in their suitability for overwintering of the pear decline agent (Seemüller et al., 1984a, b; Poggi Pollini et al., 1995a). Furthermore, it is not transmitted during the winter by scions as the phytoplasma remains in the root at that time because of the degeneration of sieve tubes in winter (Seemüller et al., 1986, 1989). Generally pear decline phytoplasma do not persist in quince rootstock during winter due to the resistance of these rootstocks to the phytoplasma.

The pear psyllids Cacopsylla pyricola, C. pyrisuga and C. pyri are the vectors of PD phytoplasma and they are mainly responsible for spreading the disease in the field (Jensen et al., 1964). The epidemiology of the disease is still poorly understood. A limiting factor in epidemiological studies has been the lack of techniques available to detect phytoplasma in the vector. Molecular diagnostic methods have been developed in order to detect phytoplasmas (Davies et al., 1995; Marzachì et al., 1998).

Vectors and Intermediate Hosts

Top of page

Diagnosis

Top of page Biological Assay

Positive identification requires transmission on a woody indicator (see Detection and Inspection Methods).

The transmission test performed by grafting root or stem scions onto P. communis cv. Precocious in the glasshouse produces symptoms at the end of the growing season (Seemüller, 1989).

Among several indicators evaluated under controlled conditions, Cydonia oblonga C 7-1 seems the most reliable for screening propagative material. It takes 40 days, after tongue graft transmission, instead of 2 years of field testing to produce symptoms due to the phytoplasma infection They consist of tufts of small leaves (rosette), leaf yellowing and distortion of the leaf blade. The only symptom observed on the other indicators is the presence of elongated petioles (Del Serrone et al., 1998).

The use of DAPI reagent (1,6 diamidino 2-phenylindole) to detect phytoplasmas in the sieve tubes of the phloem tissue under the bark of infected pear trees, can help to eliminate other abiotic causes such rootstocks-scion incompatibility, malnutrition, and winter injury that induce similar symptomatology (Seemüller, 1976).

Molecular Assay

DNA extraction

Midrib and main vein tissue (1 g) should be used from leaves collected in August-September, avoid any large necrotic areas. The enriched phytoplasmas procedure is then used to obtain DNA useful for PCR.

- Incubate the tissue in 6 ml of grinding buffer on ice for 10 min.
- Grind the tissue, then add 8 ml of fresh grinding buffer and grind once more.
- Centrifuge at 1100 g and 4°C for 10 min.
- Decant the supernatant then centrifuge at 14,600 g and 4°C for 25 min.
- Resuspend the pellet in 1.5 ml of warm (60°C) extraction buffer
- Incubate at 60°C for 30 min.
- Add to the lysate an equal volume of chloroform/isoamylalcohol (24:1, v/v).
- Precipitate the aqueous layer with two-third volume of -20°C isopropanol.
- Centrifuge at 15,000 g and 4°C.
- Wash the pellet with 70% ethanol.
- Dry under vacuum.
- Add 50 µg/ml RNAse at 37°C for 30 min.
- Extract with chloroform/isoamylalcohol (24:1, v/v), precipitate with ethanol, wash and dry pellet as described.

Grinding Buffer

potassium phosphate 125 mM
ascorbic acid 30 mM
sucrose 10%
bovine serum albumin (BSA V) 0.15%
polyvinylpyrrolidone (PVP 15) 2%
pH 7.6

Extraction Buffer

Hexadecyltrimethyl-ammonium bromide (CTAB) 2%
NaCl 1.4 M
2-mercaptoethanol 0.2%
Ethylendiaminetetraacetic (EDTA) 20 mM
Tris- hydroxymethylaminomethane hydrochloride (Tris-HCl) 100 mM
pH 8.0

(Ahrens and Seemüller, 1992)

Polymerase Chain Reaction (PCR)

Several primers intended for diagnosis of phytoplasma diseases have been identified.


Molecular diagnosis of pear decline phytoplasma by direct PCR

Primer pair: f01/r01

Sequence:
5' - CGG AAA CTT TTA GTT TCA GT - 3'
5' - AAG TGC CCA ACT AAA TGA T - 3'

Amplified product size: ca 1100 bp

Phytoplasma: all phytoplasma isolates of AP group

Reference: Lorenz et al. (1995)

Primer pair: fPD/r01

Sequence:
5' - GAC CCG TAA GGT ATG CTG A - 3'
5' - AAG TGC CCA ACT AAA TGA T - 3'

Amplified product size: ca 1000 bp

Phytoplasma: all phytoplasma isolates of pome fruit subgroup of AP group (AP, PD)

Reference: Lorenz et al. (1995)

Primer pair: fPD/rPDS

Sequence:
5' - GAC CCG TAA GGT ATG CTG A - 3'
5' - CCC GGC CAT TAT TAA TTT TA - 3'

Amplified product size: ca 1400 bp

Phytoplasma: specific for pear decline phytoplasma

Reference: Lorenz et al. (1995)

Primer pair: fAT/rPRUS

Sequence:
5' - CAT CAT TTA GTT GGG CAC TT - 3'
5' - GCC CCA AGC CAT TAT TGA TT - 3'

Amplified product size: ca 500 bp

Phytoplasma: all phytoplasma isolates of PD and ESFY

Reference: Smart et al. (1996)

The pair fO1/rO1 and fPD/rO1 prime in the 16S rDNA sequence and are, respectively, AP group specific and pome fruit subgroup specific.

The pairs fAT/rPRUS and fPD/rPDS prime in the 16S/23S rDNA spacer region and are specific for PD and ESFY phytoplasmas, and PD phytoplasma only, respectively.

Molecular diagnosis of pear decline phytoplasma by nested PCR

Primer pair: R16F2/R2

Sequence:
5' - ACG ACT GCT AAG GAC TGG - 3' (153-168)
5' - TGA GGG GCG GTG TGT ACA AAC CCC G - 3' (1373-1397)

Amplified product size: ca 1200 bp

Phytoplasma: all phytoplasmas

Reference: Lee et al. (1995)

Primer pair: R16(X)F1/R1

Sequence:
5' - GAC CCG CAA GTA TGC TGA GAG ATG - 3' (197-221)
5' - CAA TCC GAA CTG AGA CTG T - 3' (1198-1297)

Amplified product size: ca 1100 bp

Phytoplasma: all phytoplasmas of AP group (AP, PD, ESFY)

Reference: Lee et al. (1995)

PCR products initially amplified by using the universal primer pair R16F2/R2 are diluted (1/40) with sterile deionized water and used as template DNA for a subsequent PCR with the pair R16(X)F1/R1 These pairs prime on the 16S rDNA sequence (Lee et al., 1995).

All these primer pairs work at different reaction mixtures and conditions.

Primer pairs: fO1/rO1; fPD/rO1; fPD/rPDS

Reaction mixture: final volume: 40 µl
template: 50-100 ng
Primers: 250 nM
Buffer: 1x
dNTPs: 100 µM
Enzyme: 0.20- 1 Unit/reaction
Reaction conditions: 30 cycles
95°C for 30 s denaturation
55°C for 75 s annealing
72°C for 90 s extension

Primer pair: fAT/rPRUS

Reaction mixture: final volume: 30 µl
template: 50 ng
Primers: 0.5 µM
Buffer:1x
dNTPs: 150 µM
Enzyme: 1 Unit/reaction
Reaction conditions: 30 cycles
94°C for 60 s denaturation
55°C for 60 s annealing
72°C for 120 s extension

Primer pairs: R16F2/R2; R16(X)F2/R2

Reaction mixture: final volume: 50 µl
template: 20 ng
Primers: 0.4-1 µM
Buffer: 1x
dNTPs: 200 µM
Enzyme:1 Unit/reaction
Reaction conditions: 94°C for 120 s predenaturation step
35 cycles
94°C for 60 s denaturation
50°C for 120 s annealing
70°C for 180 s extension
72°C for 600s elongation

Restriction Fragment Length Polymorphism analysis (RFLP)

The use of PCR amplification of the 16S rDNA to differentiate phytoplasmas belonging to the same group is difficult due to the high similarity of their sequences so that it is necessary to digest the amplification products by restriction endonucleases.

Molecular characterization of PD phytoplasma with RFLP analysis of amplified products obtained with different primer pairs

Primer pair: f01/r01; fPD/r01
Endonuclease: Sfc I
Phytoplasma: PD
Reference: Lorenz et al. (1995)

Primer pair: R16F2/R2+R16(X)F2/R2
Endonuclease: Rsa I
Phytoplasma: PD
Reference: Lee et al. (1995)

Primer pair: FAT/rPRUS
Endonuclease: Alu I
Phytoplasma: PD
Reference: Poggi Pollini et al. (1995b)


PCR-ELISA

DNA amplification:
use the primer pair: fP1/rP7

P1 5' - AAG AGT TTG ATC CTG GCT CAG GAT T- 3'
P7 5' - CGT CCT TCA TCG GCT CTT-3'

This pair amplify both 16SrRNA gene and the spacer region between 16S rRNA and 23S rRNA

Reaction mixture: final volume: 30 µl
template: 50 ng
Primers: 0.5 µM
Buffer: 1x
dNTPs: 150 µM
Enzyme: 1 Unit/reaction
Reaction conditions: 30 cycles
94°C for 60 s denaturation
56°C for 60 s annealing
72°C for 120 s extension
72°C for 60 s elongation

(Smart et al., 1996).

Products obtained with the fP1/rP7 primers labelled with digoxigenin during the amplification process are hybridized after denaturation with the rPDS probe. This specific capture probe complementary to the inner part of the amplification product was biotinilated in the 5' position. The hybridization product (20 pmoles + 20µl of amplified product made up to 220 µl with hybridization solution) is incubated in an ELISA plate previously coated with streptoavidin. The test is performed according to Boehringer Mannheim manufacturing instructions following the protocol of Poggi Pollini et al. (1997). This technique is highly specific and sensitive.

Requirements for positive molecular diagnosis:

- Water instead of template DNA must be considered and added to reaction mixture for controls in PCR experiments.

- In case of negative result, it is recommended the use of universal primers to check the presence of phytoplasmas other than the pear decline phytoplasma. Suggested universal primers are: fU5/RU3 (Lorenz et al., 1995); F2n/R2 (Lee et al., 1995); and P1/Tint (Smart et al., 1996).

Then use PCR, with other group- or species-specific primers, and RFLP analysis for differentiation (Lorenz et al., 1995; Smart et al., 1996).

- Use DNA of reference strains, belonging to the same and to other groups, in all molecular diagnostic methods.

Detection and Inspection

Top of page Pear decline is routinely detected by visual observation (see Symptoms) and by field testing on Pyrus communis Doyenné du Comice; using three replicates for 2 years (OEPP/EPPO, 1991/1992).

For laboratory diagnosis, at least five samples per plant should be randomly collected for phytoplasma diagnosis in order to avoid false negatives caused by the low titre and erratic distribution of phytoplasmas in the phloem of the plant. Samples, consisting of leaves, petioles, shoots and canes, should be collected at the end of August. The use of fresh material is recommended in diagnostic assays. If this is not possible, tissue should be stored at -20°C. (See Diagnostic Methods.)

Similarities to Other Species/Conditions

Top of page Criteria that can be used to differentiate pear decline phytoplasma from other phytoplasmas and the related Mollicutes include: full-length sequence of 16S rDNA; 16S/23S spacer region sequence; RFLP of PCR-amplified ribosomal DNA products; RFLP patterns of non-ribosomal DNA (Southern analysis).

Prevention and Control

Top 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.

As a preventive measure, the use of healthy propagation material is a prerequisite. Intensive control of weeds and insect vectors in the orchards is also essential. The use of antibiotics (Nyland and Moller, 1973) can select resistant bacterial populations. Resistant rootstocks are the most efficient way to control the disease (Seemüller, 1990).

References

Top of page

===, 1978. Data sheets on quarantine organisms. Set 1. Bulletin, Organisation Europeenne et Mediterraneenne pour la Protection des Plantes, 8(2).

Avinet L, Llácer G, 1995. Detection of phytoplasmas in fruit trees by polymerase chain reaction (PCR) in Spain. Acta Horticulturae, 386:480-483.

CABI, EPPO, 1998. Pear decline phytoplasma. [Distribution map]. Distribution Maps of Plant Diseases, October (Edition 1). Wallingford, UK: CAB International, Map 769.

CABI/EPPO, 1998. Distribution maps of quarantine pests for Europe (edited by Smith IM, Charles LMF). Wallingford, UK: CAB International, xviii + 768 pp.

CABI/EPPO, 2013. Candidatus Phytoplasma pyri. [Distribution map]. Distribution Maps of Plant Diseases, No.October. Wallingford, UK: CABI, Map 769 (Edition 2).

Choueiri E, Salar P, Jreijiri F, El-Zammar S, Danet JL, Foissac X, 2007. First report and characterization of pear decline phytoplasma on pear in Lebanon. Journal of Plant Pathology, 89(Suppl.3):S75. http://www.agr.unipi.it/sipav/jpp/index.html

Davies DL, Barbara DJ, Clark MF, 1995. The detection of MLOs associated with pear decline in pear trees and pear psyllids by polymerase chain reaction. Acta Horticulturae, No. 386:484-488; 4 ref.

Davies DL, Guise CM, Clark MF, Adams AN, 1992. Parry's disease of pears is similar to pear decline and is associated with mycoplasma-like organisms transmitted by Cacopsylla pyricola. Plant Pathology, 41(2):195-203

Davis RE, Dally EL, Gundersen DE, Lee IngMing, Habili N, 1997. "Candidatus phytoplasma australiense", a new phytoplasma taxon associated with Australian grapevine yellows. International Journal of Systematic Bacteriology, 47(2):262-269; 45 ref.

Del Serrone P, Barrale R, Liberatore A, Bianchi E, Barba M, 1998. Cydonia oblonga C 7-1: a reliable biological indicator for pear decline disease. Journal of Plant Pathology, 80(3):256.

EPPO, 2011. EPPO Reporting Service. EPPO Reporting Service. Paris, France: EPPO. http://archives.eppo.org/EPPOReporting/Reporting_Archives.htm

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

EPPO/CABI, 1996b. Pear decline phytoplasma. In: Quarantine pests for Europe. 2nd edn. Wallingford, UK: 1048-1052.

Facundo, R., Quiroga, N., Méndez, P., Zamorano, A., Fiore, N., 2017. First report of 'Candidatus phytoplasma pyri' on pear in Chile., Plant Disease, 101(5):830 http://apsjournals.apsnet.org/loi/pdis

Firrao G, Gobbi E, Locci R, 1994. Rapid diagnosis of apple proliferation mycoplasma-like organism using a polymerase chain reaction procedure. Plant Pathology, 43(4):669-674

Gazel M, Serçe ÇU, Çaglayan K, Öztürk H, 2007. . http://www.bulletinofinsectology.org/

Giunchedi L, Poggi Pollini C, Bissani R, Babini AR, Vicchi V, 1995. Etiology of a pear decline disease in Italy and susceptibility of pear variety and rootstock to phytoplasma-associated pear decline. Acta Horticulturae, No. 386:489-495; 5 ref.

Giunchedi L, Pollini CP, Biondi S, Babini AR, 1994. PCR detection of MLOs in quick decline-affected pear trees in Italy. Annals of Applied Biology, 124(2):399-403

Gundersen DE, Lee IM, Rehner SA, Davis RE, Kingsbury DT, 1994. Phylogeny of mycoplasmalike organisms (Phytoplasmas): a basis for their classification. Journal of Bacteriology, 176(17):5244-5254

Hibino H, Schneide, 1970. Mycoplasma bodies in sieve tubes of pear trees affected with pear decline. Phytopathology, 60:499-501.

Hibino H., Kaloostran G. H., Scheneider H., 1971. Mycoplasma-like bodies in the pear psylla vector of pear decline. Virology 43, 34-40.

Hunter DM, Svircev AM, Kaviani M, Michelutti R, Wang L, Thompson D, 2010. First report of pear decline caused by 'Candidatus Phytoplasma pyri' in Ontario, Canada. Plant Disease, 94(5):634. http://apsjournals.apsnet.org/loi/pdis

IPPC, 2016. Information on Pest Status in the Republic of Lithuania in 2015. IPPC Official Pest Report, No. LTU-01/2. Rome, Italy: FAO. https://www.ippc.int/

Jarausch W, Saillard C, Dosba F, Bové J-M, 1994. Differentiation of mycoplasmalike organisms (MLOs) in European fruit trees by PCR using specific primers derived from the sequence of a chromosomal fragment of the apple proliferation MLO. Applied and Applied Environmental Microbiology, 60(8):2916-2923.

Jensen DD, Greggs WH, Gonzales CQ, Schneider H, 1964. Pear decline virus transmission by pear psylla. Phytopathology, 54:1346.

Khalifa MB, Marrakchi M, Fakhfakh H, 2007. Candidatus Phytoplasma pyri infections in pear orchards in Tunisia. Journal of Plant Pathology, 89(2):269-272. http://www.agr.unipi.it/sipav/jpp/index.html

Kirkpatrick BC, Smart C, Gardener S, Gao J-L, Ahrens U, MSurer R, Schneider B, Daire X, 1994. Phylogenetic relationship of plant pathogenic MLOs established by 16S/23S rDNA spacer sequences. IOM Letters, 3:228-229.

Kison H, Schneider B, Seemuller E, 1994. Restriction fragment length polymorphisms within the apple proliferation mycoplasmalike organism. Journal of Phytopathology, 141(4):395-401

Kucerová J, Karesová R, Navrátil M, Válová P, 2007. . http://www.bulletinofinsectology.org/

Kucerová J, Talácko L, Lauterer P, Navrátil M, Fialová R, 2007. . http://www.bulletinofinsectology.org/

Lee IM, Bertaccini A, Vibio M, Gundersen DE, 1995. Detection of multiple phytoplasmas in perennial fruit trees with decline symptoms in Italy. Phytopathology, 85(6):728-735

Lee IM, Hammond RW, Davis RE, Gundersen DE, 1993. Universal amplification and analysis of pathogen 16S rDNA for classification and identification of mycoplasmalike organisms. Phytopathology, 83(8):834-842

Lim PO, Sears BB, 1992. Evolutionary relationships of a plant-pathogenic mycoplasmalike organism and Acholeplasma laidlawii deduced from two ribosomal protein gene sequences. Journal of Bacteriology, 174(8):2606-2611

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

Lorenz KH, Schneider B, Ahrens U, Seemuller E, 1995. Detection of the apple proliferation and pear decline phytoplasmas by PCR amplification of ribosomal and nonribosomal DNA. Phytopathology, 85(7):771-776

Marcone C, Ragozzino A, Seemnller E, 1996. Association of phytoplasmas with the decline of European hazel in southern Italy. Plant Pathology, 45(5):857-863; 25 ref.

Marcone C, Ragozzino A, Seemnller E, 1996. European stone fruit yellows phytoplasma as the cause of peach vein enlargement and other yellows and decline diseases of stone fruits in southern Italy. Journal of Phytopathology, 144(11-12):559-564; 26 ref.

Marzach C, Veratti F, Bosco D, 1998. Direct PCR detection of phytoplasmas in experimentally infected insects. Annals of Applied Biology, 133:45-54.

Myrta A, Martini M, Susuri L, Susuri HSh, Carraro L, 2006. First report of apple proliferation and pear decline phytoplasmas in Kosovo. Journal of Plant Pathology, 88(1):125. http://www.agr.unipi.it/sipav/jpp/index.html

Németh M, 1986. Virus, Mycoplasma and Rickettsia Diseases of Fruit Trees. Lancaster, Boston, USA/Dordrecht, Netherlands: M. Nijhoff Publishers, 841 pp.

Nyland G, Moller WJ, 1973. Control of pear decline with a tetracycline. Plant Disease Reporter, 57(8):634-637

OEPP/EPPO, 1991/1992. Certification schemes. Virus-free or virus-tested fruit trees and rootstocks. Bulletin OEPP/EPPO Bulletin, 21:267-278; 22:253-284.

Pastore M, Lee I-M, Vibio M, Santonastaso M, La Cara F, Bertaccini A, 1997. Pear decline infection of three pear varieties grafted on different rootstocks in Southern Italy. In: Proceedings of the XVIIth International Symposium on virus and virus like diseases of temperate fruit crops. June 23-27, Bethseda, Maryland, USA, 98-99.

Poggi Pollini C, Bissani R, Giunchedi L, 1995. Overwintering of pear decline agent in some quince rootstocks. Acta Horticulturae, No. 386:496-499; 10 ref.

Pollini CP, Bissani R, Giunchedi L, Vindimian E, 1995. Occurrence of phytoplasma infection in European plums (Prunus domestica). Journal of Phytopathology, 143(11-12):701-703; 19 ref.

Pollini CP, Giunchedi L, Bissani R, 1997. Immunoenzymatic detection of PCR products for the identification of phytoplasmas in plants. Journal of Phytopathology, 145(8/9):371-374; 14 ref.

Refatti E, 1967. Pear decline and moria. Technical Communication of Commonwealth Bureau Horticultural Plantation Crops, 30(1): 108a-108h.

Sabaté J, Laviña A, Batlle A, 2014. First report of 'Candidatus Phytoplasma pyri' causing peach yellow leaf roll (PYLR) in Spain. Plant Disease, 98(7):989-990. http://apsjournals.apsnet.org/loi/pdis

Salehi M, Izadpanah K, Taghavi SM, Rahimian H, 2008. Characterization of a phytoplasma associated with pear decline in Iran. Journal of Phytopathology, 156(7/8):493-495. http://www3.interscience.wiley.com/cgi-bin/fulltext/120174270/HTMLSTART

Schneider B, Ahrens U, Kirkpatrick BC, Seemüller E, 1993. Classification of plant-pathogenic mycoplasma-like organisms using restriction-site analysis of PCR-amplified 16S rDNA. Journal of General Microbiology, 139(3):519-527

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.

Seemuller E, Kunze L, Schaper U, 1984. Colonization behaviour of MLO, and symptom expression of proliferation-diseased apple trees and decline-diseased pear trees over a period of several years. Zeitschrift fur Pflanzenkrankheiten und Pflanzenschutz, 91(5):525-532

Seemuller E, Schaper U, Kunze L, 1986. Effect of pear decline on pear trees on 'Quince A' and Pyrus communis seedling rootstocks. Zeitschrift fur Pflanzenkrankheiten und Pflanzenschutz, 93(1):44-50

Seemüller E, 1976. Demonstration of mycoplasma-like organisms in the phloem of trees with pear decline or proliferation symptoms by fluorescence microscopy. Phytopatholigische Zeitschrift, 85:368-372.

Seemüller E, 1990. Pear decline. In: Virus and virus-like diseases of pome fruits and simulating non-infectious disorders; Fridlund PR, ed. Washington State University, Co-operative Extension, Special Publication N° SP0003. Washington State University, Pullman, USA.. American Phytopathological Society, St. Paul, Minnesota, USA.

Seemüller E, Schaper U, Zimbelmann F, 1984. Seasonal variation in the colonisation patterns of mycoplasma-like organisms associated with apple proliferation and pear decline. Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz, 91:371-382.

Seemüller E, Schneider B, 2004. ’Candidatus Phytoplasma mali’, ’Candidatus Phytoplasma pyri’ and ’Candidatus Phytoplasma prunorum’, the causal agents of apple proliferation, pear decline and European stone fruit yellows, respectively. International Journal of Systematic and Evolutionary Microbiology, 54(4):1217-1266.

Seemüller E, Schneider B, Maürer R, Ahrens U, Daire X, Kison H, Lorenz KH, Firrao G, Avinent L, Sears BB, Stackebrandt E, 1994. Phylogenetic classification of phytopathogenic mollicutes by sequence analysis of 16S ribosomal DNA. International Journal of Systematic Bacteriology, 44(3):440-446

Serrone P del, Starza Sla, Krystai L, Kolber M, Barba M, 1998. Occurrence of apple proliferation and pear decline phytoplasmas in diseased pear trees in Hungary. Journal of Plant Pathology, 80(1):53-58; 14 ref.

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.

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.

Topchiiska M, Sakalieva D, 2001. Detection of pear decline phytoplasma by polymerase chain reaction in Bulgaria. Bulgarian Journal of Agricultural Science, 7(6):611-614.

Vega FE, Davis RE, Barbosa P, Dally EL, Purcell AH, Lee IM, 1993. Detection of a plant pathogen in a nonvector insect species by the polymerase chain reaction. Phytopathology, 83(6):621-624

Weisburg WG, Tully JG, Rose DL, Petzel JP, Oyaizu H, Yang D, Mandelco L, Sechrest J, Lawrence TG, Etten Jvan, Maniloff J, Woese CR, 1989. A phylogenetic analysis of the mycoplasmas: basis for their classification. Journal of Bacteriology, 171(12):6455-6467; 50 ref.

Westwood MN, Cameron HR, 1978. Environment-induced remission of pear decline symptoms. Plant Disease Reporter, 62(2):176-179

Distribution References

Avinet L, Llácer G, 1995. Detection of phytoplasmas in fruit trees by polymerase chain reaction (PCR) in Spain. In: Acta Horticulturae, 386 480-483.

CABI, Undated. Compendium record. Wallingford, UK: CABI

CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

CABI/EPPO, 2013. Candidatus Phytoplasma pyri. [Distribution map]. In: Distribution Maps of Plant Diseases, Wallingford, UK: CABI. Map 769 (Edition 2).

Choueiri E, Salar P, Jreijiri F, El-Zammar S, Danet J L, Foissac X, 2007. First report and characterization of pear decline phytoplasma on pear in Lebanon. Journal of Plant Pathology. 89 (Suppl.3), S75. http://www.agr.unipi.it/sipav/jpp/index.html

Del Serrone P, Barrale R, Liberatore A, Bianchi E, Barba M, 1998. Cydonia oblonga C 7-1: a reliable biological indicator for pear decline disease. In: Journal of Plant Pathology, 80 (3) 256.

EPPO, 2020. EPPO Global database. In: EPPO Global database, Paris, France: EPPO.

Facundo R, Quiroga N, Méndez P, Zamorano A, Fiore N, 2017. First report of 'Candidatus phytoplasma pyri' on pear in Chile. Plant Disease. 101 (5), 830. http://apsjournals.apsnet.org/loi/pdis DOI:10.1094/PDIS-08-16-1144-PDN

Gazel M, Serçe Ç U, Çağlayan K, Öztürk H, 2007. Detection of 'Candidatus Phytoplasma pyri' in Turkey. Bulletin of Insectology. 60 (2), 125-126. http://www.bulletinofinsectology.org/

Giunchedi L, Pollini C P, Biondi S, Babini A R, 1994. PCR detection of MLOs in quick decline-affected pear trees in Italy. Annals of Applied Biology. 124 (2), 399-403. DOI:10.1111/j.1744-7348.1994.tb04143.x

Hunter D M, Svircev A M, Kaviani M, Michelutti R, Wang L, Thompson D, 2010. First report of pear decline caused by 'Candidatus Phytoplasma pyri' in Ontario, Canada. Plant Disease. 94 (5), 634. http://apsjournals.apsnet.org/loi/pdis DOI:10.1094/PDIS-94-5-0634B

IPPC, 2016. Information on Pest Status in the Republic of Lithuania in 2015. In: IPPC Official Pest Report, No. LTU-01/2, Rome, Italy: FAO. https://www.ippc.int/

Jarausch W, Saillard C, Dosba F, Bové J-M, 1994. Differentiation of mycoplasmalike organisms (MLOs) in European fruit trees by PCR using specific primers derived from the sequence of a chromosomal fragment of the apple proliferation MLO. In: Applied and Applied Environmental Microbiology, 60 (8) 2916-2923.

Khalifa M B, Marrakchi M, Fakhfakh H, 2007. Candidatus Phytoplasma pyri infections in pear orchards in Tunisia. Journal of Plant Pathology. 89 (2), 269-272. http://www.agr.unipi.it/sipav/jpp/index.html

Kirkpatrick BC, Smart C, Gardener S, Gao J-L, Ahrens U, MSurer R, Schneider B, Daire X, 1994. Phylogenetic relationship of plant pathogenic MLOs established by 16S/23S rDNA spacer sequences. In: IOM Letters, 3 228-229.

Lorenz K H, Schneider B, Ahrens U, Seemüller E, 1995. Detection of the apple proliferation and pear decline phytoplasmas by PCR amplification of ribosomal and nonribosomal DNA. Phytopathology. 85 (7), 771-776. DOI:10.1094/Phyto-85-771

Myrta A, Martini M, Susuri L, Susuri H Sh, Carraro L, 2006. First report of apple proliferation and pear decline phytoplasmas in Kosovo. Journal of Plant Pathology. 88 (1), 125. http://www.agr.unipi.it/sipav/jpp/index.html

Németh M, 1986. Virus, Mycoplasma and Rickettsia Diseases of Fruit Trees., Lancaster, Boston; Dordrecht, USA; Netherlands: M. Nijhoff Publishers. 841 pp.

NPPO of the Netherlands, 2013. Pest status of harmful organisms in the Netherlands., Wageningen, Netherlands:

Salehi M, Izadpanah K, Taghavi S M, Rahimian H, 2008. Characterization of a phytoplasma associated with pear decline in Iran. Journal of Phytopathology. 156 (7/8), 493-495. http://www3.interscience.wiley.com/cgi-bin/fulltext/120174270/HTMLSTART DOI:10.1111/j.1439-0434.2007.01375.x

Topchiiska M, Sakalieva D, 2001. Detection of pear decline phytoplasma by polymerase chain reaction in Bulgaria. Bulgarian Journal of Agricultural Science. 7 (6), 611-614.

Distribution Maps

Top of page