Spiroplasma kunkelii (corn stunt spiroplasma)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Hosts/Species Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Seedborne Aspects
- Vectors and Intermediate Hosts
- Detection and Inspection
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Spiroplasma kunkelii Whitcomb, Chen et al., 1986
Preferred Common Name
- corn stunt spiroplasma
International Common Names
- English: corn stunt disease; cSD; cSS; maize stunt spiroplasma; mSS; rio Grande corn stunt
- SPIRKU (Spiroplasma kunkelii)
Taxonomic TreeTop of page
- Domain: Bacteria
- Phylum: Firmicutes
- Class: Mollicutes
- Order: Entomoplasmatales
- Family: Spiroplasmataceae
- Genus: Spiroplasma
- Species: Spiroplasma kunkelii
Notes on Taxonomy and NomenclatureTop of page In 1975 the causal organism of Rio Grande corn stunt disease was identified as a mycoplasma (Bradfute et al., 1981) and separated from other organisms associated with corn stunt, namely maize bushy stunt mycoplasma and maize chlorotic dwarf virus (Lee and Davis, 1988; Golino and Oldfield, 1990; Whitcomb et al., 1986). Spiroplasmas in Florida (Jordan et al., 1989) and California (Nault, 1990), originally considered distinct from the Rio Grande pathogen, are now considered to be different strains (Bajet and Renfro, 1989). Differences in symptomatology between strains are now attributed to environment, cultivar, and other micro-organisms present (Bajet and Renfro, 1989).
Nine strains of spiroplasma subgroup I-3 (agent of corn stunt disease) were similar in their serological properties. Strain E275T was shown to belong to the class Mollicutes by the ultrastructure of the limiting membrane, its prokaryotic organization, colonial morphology and filtration behaviour, and to the family Spiroplasmataceae by its helical morphology and motility (Whitcomb et al., 1986).
DescriptionTop of page A helical, motile, cell wall-free procaryote, bounded by a single membrane. Cells are approximately 0.15-0.2 µm in diameter, 2.0-15 µm in length and 0.4-0.6 µm in amplitude of the helical gyre, with a regular gyre length in a given helical filament. The cells are able to pass through a membrane filter of 220 nm pore size, but not through 100-nm pores. Cell dimensions vary slightly with medium in vitro cultivation. Helical cells exhibit flexional and rotational motility, with translational movement in viscous media (Bradbury, 1991).
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.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Mexico||Present||Davis et al., 1981; Bajet and Renfro, 1989; CABI/EPPO, 2008; EPPO, 2014|
|USA||Present||CABI/EPPO, 2008; EPPO, 2014|
|-California||Present||Purcell, 1988; CABI/EPPO, 2008; EPPO, 2014|
|-Florida||Present||CABI/EPPO, 2008; EPPO, 2014|
|-Louisiana||Present||Davis et al., 1981; CABI/EPPO, 2008; EPPO, 2014|
|-Michigan||Present||CABI/EPPO, 2008; EPPO, 2014|
|-Mississippi||Present||Lee and Davis, 1989; CABI/EPPO, 2008; EPPO, 2014|
|-Ohio||Present||CABI/EPPO, 2008; EPPO, 2014|
|-Texas||Present||Davis et al., 1981; CABI/EPPO, 2008; EPPO, 2014|
Central America and Caribbean
|Belize||Present||CABI/EPPO, 2008; EPPO, 2014|
|El Salvador||Present||Davis et al., 1981; CABI/EPPO, 2008; EPPO, 2014|
|Guatemala||Present||CABI/EPPO, 2008; EPPO, 2014|
|Honduras||Present||CABI/EPPO, 2008; EPPO, 2014|
|Jamaica||Present||Eden-Green, 1982; CABI/EPPO, 2008; EPPO, 2014|
|Nicaragua||Present||CABI/EPPO, 2008; EPPO, 2014|
|Panama||Present||CABI/EPPO, 2008; EPPO, 2014|
|Argentina||Restricted distribution||CABI/EPPO, 2008; EPPO, 2014|
|Bolivia||Present||CABI/EPPO, 2008; EPPO, 2014|
|Brazil||Present||Hammond and Bedendo, 2001; CABI/EPPO, 2008; EPPO, 2014|
|-Mato Grosso do Sul||Present||CABI/EPPO, 2008; EPPO, 2014|
|-Minas Gerais||Present||CABI/EPPO, 2008; EPPO, 2014|
|Colombia||Present||CABI/EPPO, 2008; EPPO, 2014|
|Paraguay||Present||CABI/EPPO, 2008; EPPO, 2014|
|Peru||Present||Nault et al., 1979; Davis et al., 1981; CABI/EPPO, 2008; EPPO, 2014|
|Venezuela||Present||Davis et al., 1981; CABI/EPPO, 2008; EPPO, 2014|
Risk of IntroductionTop of page Economic Importance: Low
Distribution: Western hemisphere
Seedborne Incidence: One report indicated that it was isolated onto culture media from maize seeds (mcg19).
Seed Transmitted: Not recorded
Seed Treatment: None
Overall Risk: Moderate
S. kunkelii is restricted in distribution to the western hemisphere, and is listed by the APPPC as an A1 quarantine risk.
Hosts/Species AffectedTop of page Zea mays is the primary natural host crop of S. kunkelii, but Euchleana mexicana [Zea mexicana] and E. perennis [Z. perennis] are known experimental hosts and may be involved in the epidemiology of the disease (Bradbury, 1991; Nault, 1980). Corn stunt spiroplasmas were experimentally transmitted to two dicotyledons, Vinca rosea [Catharanthus roseus] and Vicia faba by leafhoppers that had been injected with broth cultures of the organisms (Markham et al., 1977).
Growth StagesTop of page Flowering stage, Fruiting stage, Seedling stage, Vegetative growing stage
SymptomsTop of page Chlorosis of leaf margins is the first symptom of S. kunkelii infection, followed by reddening of tips of older leaves (some maize varieties do not redden). Small chlorotic spots appear 2-4 days later at the bases of newly developing leaves. In successive leaves above those bearing first symptoms, the chlorotic spots coalesce to form stripes that extend towards the leaf tips until entire leaves are affected. Later-emerging leaves may also develop chlorosis of the margins, yellowing or reddening, tearing, twisting, and are shortened. Plants are stunted and numerous ear shoots develop. Numerous tillers may also develop at the leaf axils and base of the plant, giving it a bushy appearance.
Symptoms of corn stunt spiroplasma observed in Mexico varied with altitude. Some plants were consistently stunted with well-defined broad chlorotic streaking on the leaves. These symptoms are usually observed between 60 amd 940 m above sea level. Plants that were not always stunted but whose leaf margins showed red to purple streaks, and plants that usually were not stunted but whose leaves showed either a diffuse yellow or a chlorotic stripe condition with or without red margins, were observed at all elevations surveyed and usually appeared around 7 days before or after anthesis. ELISA was better than DFM at detecting S. kunkelii, but both methods demonstrated that all samples with the first type of symptom, 51-70% of those with the second type, 43-46% of those with the third type and 3-11% of those without symptoms were infected by S. kunkelii. The disease was more prevalent at lower than at higher elevations. These results indicate high prevalence and wide distribution of this spiroplasma in Mexico, and also confirm that maize plants having reddish or purplish leaves are often infected with S. kunkelii (Bajet and Renfro, 1989).
List of Symptoms/SignsTop of page
|Inflorescence / discoloration panicle|
|Inflorescence / twisting and distortion|
|Leaves / abnormal colours|
|Leaves / abnormal forms|
|Leaves / necrotic areas|
|Leaves / yellowed or dead|
|Stems / witches broom|
|Whole plant / dwarfing|
Biology and EcologyTop of page The leafhoppers Dalbulus maidis, D. eliminatus, Exitianus exitiosus, Graminella nigrifons and Stirellus bicolor are vectors for the pathogen (Alivizatos and Markham, 1986; Madden and Nault, 1983).
Symptoms of corn stunt spiroplasma observed in Mexico varied with altitude. Some plants were consistently stunted with well-defined broad chlorotic streaking on the leaves. These symptoms were usually observed between 60 and 940 m above sea level. Plants that were not always stunted but whose leaf margins showed red to purple streaks, and plants that usually were not stunted but whose leaves showed either a diffuse yellow or a chlorotic stripe condition with or without red margins, were observed at all elevations surveyed and usually appeared around 7 days before or after anthesis. All samples with the first type of symptom, 51-70% of those with the second type, 43-46% of those with the third type and 3-11% of those without symptoms were infected by S. kunkelii. The disease was more prevalent at lower than at higher elevations. These results indicate high prevalence and wide distribution of this spiroplasma in Mexico, and also confirm that maize plants having reddish or purplish leaves are often infected with S. kunkelii (Bajet and Renfro, 1989).
Several strains of S. kunkelii were cloned in triplicate from one primary pure culture. All new strains were serologically closely related to known strains of S. kunkelii, but PAGE of membrane proteins revealed minor differences. Some were helical in cell shape, some were non-helical, and some were partially helical, consisting of helical and non-helical regions in the same cell (Lee and Davis, 1989). Nine strains of spiroplasma subgroup I-3 (agent of corn stunt disease) were similar in their serological properties. Strain E275T was shown to belong to the class Mollicutes by the ultrastructure of the limiting membrane, its prokaryotic organization, colonial morphology and filtration behaviour, and to the family Spiroplasmataceae by its helical morphology and motility (Whitcomb et al., 1986).
Seedborne AspectsTop of page Incidence
One report indicated that the pathogen was isolated onto culture media from maize seeds (Periera and Oliviera, 1971).
Effect on Seed Quality
Diseased plants are stunted and bear numerous small ear shoots. No seeds are produced on severely infected plants (McGee, 1988).
Seed Health Tests
The pathogen was isolated from seed onto culture media (Periera and Oliviera, 1971).
Vectors and Intermediate HostsTop of page
ImpactTop of page S. kunkelii is an important disease in lowlands of tropical central and south America (Nault, 1983). It has been reported in Texas, Louisiana and Florida, but only as a minor disease (Bradfute et al., 1981; Davis et al., 1981).
DiagnosisTop of page C-3G medium or C-3GH (HEPES buffer added) containing gamma globulin-free horse serum may be used for the isolation and growth of S. kunkelii (Liao and Chen, 1977; Davis, 1990).
On serum-free medium LD59, non-helical strains of S. kunkelii produce minute 'fried egg' colonies (approximately 0.2 mm in diameter after 20 days' incubation), while partially helical strains produce small colonies with granular centres surrounded by satellite colonies. Strains with normal helicity in general produce large, uniformly diffuse colonies (up to 2 mm), but one helical strain (I-15) appeared to be non-motile in broth culture and it exhibited little translational motility in agar medium, accounting for development of minute granular colonies (approximately 0.2 mm in diameter) (Lee and Davis, 1989).
The pathogen can also be detected in plant tissues by ELISA (Gordon et al., 1985).
Detection and InspectionTop of page On the whole plant look for stunting, numerous ear shoots and excessive root branching. On the leaf look for chlorotic spots which coalesce to form broad, yellow stripes extending toward the leaf tips. Later, these turn purple-red.
ReferencesTop of page
Davis MJ, 1990. In: Klement, Rudolph, Sands, eds. Methods in Phytopathology. Budapest: Akademiai Kiado, 75-86.
Davis RE; Chen TA; Worley JF, 1981. Corn stunt spiroplasma. In: Gordon DT, Knoke JK, Scott GE, eds.Virus and Viruslike Diseases of Maize in the United States. South. Coop. Ser. Bull. 247, 40-50.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Jordan RL; Konai M; Lee IM; Davis RE, 1989. Species-specific and cross-reactive monoclonal antibodies to the plant-pathogenic spiroplasmas Spiroplasma citri and S. kunkelii. Phytopathology, 79(8):880-887
Lee IM; Davis RE, 1988. New developments in the culture of Spiroplasma kunkelii, the corn stunt spiroplasma. Mycoplasma diseases of crops. Basic and applied aspects [edited by Maramorosch, K.; Raychaudhuri, S.P.] New York, USA; Springer-Verlag, 131-139
Nault LR, 1983. Origins in Mesoamerica of maize viruses and mycoplasmas and their leafhopper vectors. In: Plumb RT, Thresh JM, ed. Plant virus epidemiology. The spread and control of insect-borne viruses Blackwell Scientific Publications Oxford United Kingdom, 259-266
Periera ALG; Oliviera BS, 1971. Causal agent of maize stunt infection isolated in culture media. Biologico, 37:215.
Whitcomb RF; Chen TA; Williamson DL; Liao C; Tully JG; Bove JM; Mouches C; Rose DL; Coan ME; Clark TB, 1986. Spiroplasma kunkelii sp. nov.: characterization of the etiological agent of corn stunt disease. International Journal of Systematic Bacteriology, 36(2):170-178
Distribution MapsTop of page
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