Phytoplasma pyri (pear decline)
Index
- Pictures
- Identity
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution
- Distribution Table
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- Symptoms
- List of Symptoms/Signs
- Biology and Ecology
- Vectors and Intermediate Hosts
- Diagnosis
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- References
- Distribution Maps
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Top of pagePreferred 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 pagePhytoplasmas, 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 pageSee also CABI/EPPO (1998, No. 269).
Distribution Table
Top of pageThe 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: 12 May 2022Continent/Country/Region | Distribution | Last Reported | Origin | First Reported | Invasive | Reference | Notes |
---|---|---|---|---|---|---|---|
Africa |
|||||||
Libya | Present | ||||||
Tunisia | Present | ||||||
Asia |
|||||||
Azerbaijan | Present | ||||||
Iran | Present | ||||||
Israel | Present, Localized | ||||||
Lebanon | Present | ||||||
Taiwan | Absent, Unconfirmed presence record(s) | ||||||
Turkey | Present | ||||||
Europe |
|||||||
Albania | Present | ||||||
Austria | Present, Few occurrences | ||||||
Belarus | Present, Localized | ||||||
Belgium | Present, Localized | ||||||
Bosnia and Herzegovina | Present | ||||||
Bulgaria | Present, Transient under eradication | ||||||
Croatia | Present, Localized | 1976 | |||||
Czechia | Present, Localized | ||||||
Estonia | Absent, Confirmed absent by survey | ||||||
France | Present, Localized | ||||||
Germany | Present, Localized | ||||||
Greece | Present, Localized | ||||||
Hungary | Present | ||||||
Italy | Present, Widespread | ||||||
Lithuania | Absent, Confirmed absent by survey | ||||||
Moldova | Present | ||||||
Netherlands | Present, Widespread | Present, in all parts of the area. | |||||
Norway | Present, Localized | ||||||
Poland | Present, Localized | 1995 | |||||
Portugal | Present, Few occurrences | ||||||
Romania | Present | ||||||
Russia | Absent, Invalid presence record(s) | ||||||
Serbia | Present, Localized | ||||||
Serbia and Montenegro | Present, Localized | ||||||
Slovakia | Present, Localized | ||||||
Slovenia | Present, Localized | ||||||
Spain | Present, Few occurrences | ||||||
Switzerland | Present, Widespread | ||||||
United Kingdom | Present, Localized | ||||||
-England | Present, Localized | ||||||
North America |
|||||||
Canada | Present, Localized | ||||||
-British Columbia | Absent, Unconfirmed presence record(s) | 1948 | |||||
-Ontario | Present | ||||||
United States | Present, Localized | 1946 | |||||
-California | Present | ||||||
-Connecticut | Present | ||||||
-Oregon | Present | ||||||
-Utah | Present | ||||||
-Washington | Present | ||||||
Oceania |
|||||||
Australia | Absent, Unconfirmed presence record(s) | ||||||
-South Australia | Absent, Unconfirmed presence record(s) | ||||||
-Victoria | Absent, Unconfirmed presence record(s) | ||||||
South America |
|||||||
Argentina | Present, Localized | ||||||
Chile | Present |
Hosts/Species Affected
Top of pageHighly 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 pagePlant name | Family | Context | References |
---|---|---|---|
Catharanthus roseus (Madagascar periwinkle) | Apocynaceae | Other | |
Corylus avellana (hazel) | Betulaceae | Other | |
Cydonia oblonga (quince) | Rosaceae | Other | |
Malus domestica (apple) | Rosaceae | Other | |
Prunus avium (sweet cherry) | Rosaceae | Unknown | |
Prunus persica (peach) | Rosaceae | Other | |
Prunus salicina (Japanese plum) | Rosaceae | Other | |
Pyrus communis (European pear) | Rosaceae | Main | |
Pyrus pyrifolia (Oriental pear tree) | Rosaceae | Other |
Symptoms
Top of pageA 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 pageSign | Life Stages | Type |
---|---|---|
Fruit / discoloration | ||
Fruit / reduced size | ||
Leaves / abnormal colours | ||
Leaves / leaves rolled or folded | ||
Stems / internal red necrosis | ||
Whole plant / distortion; rosetting | ||
Whole plant / dwarfing |
Biology and Ecology
Top of pageThe 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 pageVector | Source | Reference | Group | Distribution |
---|---|---|---|---|
Cacopsylla pyri | Insect | |||
Cacopsylla pyricola | Insect |
Diagnosis
Top of pagePositive 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 pageFor 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 pagePrevention and Control
Top of pageDue 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 pageAvinet L, Llácer G, 1995. Detection of phytoplasmas in fruit trees by polymerase chain reaction (PCR) in Spain. Acta Horticulturae, 386:480-483.
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
Gazel M, Serçe ÇU, Çaglayan K, Öztürk H, 2007. . http://www.bulletinofinsectology.org/
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.
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.
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.
Kucerová J, Karesová R, Navrátil M, Válová P, 2007. . http://www.bulletinofinsectology.org/
Marzach C, Veratti F, Bosco D, 1998. Direct PCR detection of phytoplasmas in experimentally infected insects. Annals of Applied Biology, 133:45-54.
Németh M, 1986. Virus, Mycoplasma and Rickettsia Diseases of Fruit Trees. Lancaster, Boston, USA/Dordrecht, Netherlands: M. Nijhoff Publishers, 841 pp.
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.
Refatti E, 1967. Pear decline and moria. Technical Communication of Commonwealth Bureau Horticultural Plantation Crops, 30(1): 108a-108h.
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. 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, 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.
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
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.
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.
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.
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:
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