Globodera   

 

Contents

 

Rev 11/21/2019

 Round cyst nematodes Classification Hosts
Morphology and Anatomy Life Cycle

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Economic Importance Damage
Distribution Management
Return to Heteroderidae Menu Feeding  References
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Classification:

Tylenchida
       Tylenchina
        Tylenchoidea
         Heteroderidae
          Punctoderinae

           Globodera (Skarbilovich, 1959) Behrens, 1975
   

Synonyms:        
           Tylenchus (Heterodera) (Schmidt, 1871)
           Heterodera (Heterodera) (Schmidt, 1871)
           Heterobolbus (Railliet, 1896)
           Bidera (Krall' and Krall', 1978)
           Ephippiodera (Shagalina and Krall', 1978)

Refer to Subfamily Diagnostics (Heteroderinae) for taxonomic history and distinctions among related genera.

As of 2013, the genus Globodera consists of 10 species.

Slide show on Globodera and Heterodera spp.

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Morphology and Anatomy:

Most characters of G. rostochiensis do not differ significantly from those of G. pallida. However, the adult females of G. pallida are white in contrast to the yellow color of G. rostochiensis. In addition, the juveniles of G. pallida are larger, and the stylet and tail are longer (Stone, 1973b). Stylet knobs are pointed anteriorly in G. pallida and rounded in G. rostochiensis. Adult females of G. pallida possess longer stylets than those of G. rostochiensis and have a shorter anal-vulval distance. Adult males of G. pallida have a shorter stylet width and the dorsal esophageal gland orifice is closer to the stylet knobs than in G. rostochiensis (Stone, 1973b).

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Sexual dimorphism; female swollen; males vermiform.  

Female:  body forms a cyst.  

Prominent cephalic framework and stylet.

Anterior neck-like region; swollen body shape - lemon, round, or pyroid shape (about 0.5-0.6 mm diam).

Weak cephalic framework; moderate stylet with small rounded knobs.

Metacorpus enlarged and fills neck region.  

Diovarial, prodelphic; coiled or reflexed.  

Vulva subterminal; anus terminal. 

Posterior region important taxonomically:

  • vulval cone
  • vulva position
  • presence or absence of bullae (blister-like internal projections of the body wall)
  • fenestra - thinner areas in cuticle - may break down to allow juvenile emergence - bifenestrate, circumfenestrate, etc.

Pre-parasitic stage: vermiform J2, 300-500 µm.

Heavily sclerotized head framework; head offset.

Stylet prominent with anteriorly-directed knobs.

Ventro-lateral overlap of esophageal glands over intestine.

Pointed tail. 

Post-parasitic: swollen.

Stylet weak, sometimes not visible in 3rd and 4th stage.  

Developing gonads visible.

[Ref: H. Ferris.]

Male: Vermiform, 1-1.5mm length.  

Sclerotized cephalic framework, rounded head cap.

Strong stylet; knobs project forward.  

Esophagus Tylenchid, overlaps ventro-laterally.  

Reproductive system monorchic.

Curved spicules.

No bursa.

Tail bluntly rounded.

Body size range for the species of this genus in the database - Click:
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Distribution:

Phylogenetic analyses based on DNA sequence data suggest two major Globodera spp.clades (Subbotin et al., 2011).  One clade consists of the Globodera spp. that are parasites of plants in the Solanaceae..  They include the G. tabacum group from North America and the potato cyst nematodes (G. rostochiensis and G. pallida  from South America. The other clade comprises Globodera parsites of non-solanaceous plants. They include a group of Globodera spp. that are parasites of Asteraceae and another group from the Western Cape Province of South Africa.(Knoetze et al., 2017).

 Stone (1979) suggested that the genus Globodera might have originated in the part of Gondwanaland that became South America. Recent data supports a theory that divergence of the two main Globodera groups may have occurred subsequent to the separation of Africa and South America (Subbotin et al., 2011; Knoetze et al., 2017).

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Economic Importance:

 

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Feeding:

Juveniles enter root by direct penetration of cells.

In the photograph, exposure of an infective potato cyst [Photo Nematode Secretions](Globodera rostochiensis) nematode juvenile (J2) to potato root diffusate triggered the secretion of subventral gland proteins through the stylet.  The secretions were not stimulated in water.  Secretions were stained with Coomassie Brilliant Blue G-250 (Smant et al. 1997).

The syncytium is stimulated in a cortical or endodermal cell.  The syncytium becomes multinucleate after 24 hours as adjacent cells merge.  Cell wall dissolution is through a combination of physical stress (nematode head movement) and chemical action.  Syncytia associated with developing males are usually smaller than those associated with females.  

Large sectors of the developing root, including areas that would have become vascular tissue are transfomed into syncytia.  Syncytia have many plastids, mitochondria, ribosomes, increased rough endoplasmic reticulum and enlarged lobed nuclei.  There appears to be no synthesis of DNA and nuclear division probably does not occur.  

Cell wall protruberances increase the surface area of the cell membrane for flow of solutes from the xylem to the syncytium - the transfer cell configuration (Endo, 1975).

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Hosts:

One clade of Globodera spp, originating in South America consists of species that are parasites of solanaceous plants; the other clad, consisting of species originating in Europe and Africa, appears to consist of species that are parasites of non-solanaceous plants. The first clade includes G. rostochiensis, G. pallida, G. ellingtonae and G. tabacum). The second includes the South African species, G. capensis, G.agulhasensis and G. sandveldensis (Knoetze, et al., 2017).

Host range generally narrow and specialized.  Compensated by high survival ability - up to 15 years for Globodera rostochiensis.

Several forms of delayed hatch and diapause are exhibited in the Heteroderidae.  Host-mediated hatch occurs in response to host root exudates.  

Species vary in degree of response to hatching factors:
         a) Very sensitive - hatch in water only 5% of that in host root 
            diffusate.
            G. rostochiensis, H. carotae, H. cruciferae, H. humuli
         b) Intermediate - hatch in water 10-50% of that in diffusate.
            H. schachtii, H. trifolii, H. galeopsidis.
         c) Insensitive - apparently not stimulated by diffusate.
            H. goettingiana, H. avenae, H. glycinesH. avenae requires a chill period to break diapause.
Hatching factor for G. rostochiensis thought to be a monobasic acid with molecular weight about 220 and possible formula C11H16O4. The factor breaks down rapidly in soil (results of 30 years research!).  This is an area of considerable research activity because of the potential for reducing survival.

Artificial hatching agents include Anhydrotetronic acid for G. rostochiensis, Aminoacridine (Rivanol) and ZnCl for H. schachtii.

Ecological factors also influence hatch: temperature, moisture, aeration, osmotic potential, pH, etc.   

For an extensive host range list for this genus, click
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Life Cycle:

For Ecophysiological Parameters for this genus, click 
 

J2 enters near root tip and takes position in cortex with head near vascular cylinder.  Moves intra- and intercellularly towards vascular tissues.  

During development, female breaks through cortex to surface so that most of the body of adult female remains outside root. 

Sugarbeet cyst nematode (H. schachtii) molts at 6, 12, and 15 days after entering root; matures in 19 days at 25 C.

Males are needed for reproduction in most species.  

Eggs are retained in cysts, but some are deposited in egg masses in many species.  

Distended uterus enlarges to fill body; eggs are packed in mucoid mass.

Cysts undergo a color change as they mature - from white to brown (through gold in G. rostochiensis) - due to action of polyphenol oxidase on polyphenols in the cyst wall.  The wall remains permeable to chemicals and dissolved oxygen. 

Cyst drops-off of root when dead; mucoid packing disappears.

    G. rostochiensis - 1 generation per year in Europe.
     H. schachtii - about 2 generations per year in Europe.
                    about 3 generations per year in northern California.
                     about 5 generations per year in the Imperial Valley.
     H. glycines - about 5 generations per year in North Carolina.

 

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Damage:

Little mechanical injury due to the parasitism, body of female on outside of the root and no cell division stimulated.  

Branch rootlets may be stimulated near the point of infection.  

General debilitation and reduction in efficiency of the root system. 

Chlorosis, stunted growth, wilted plants.

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Management:

Management strategies vary with species and biology.  Possibilities include prevention, crop rotation, soil fumigation, use of resistant varieties, and use of clean seed sources.

Management of these genera is usually difficult due to prolonged viability.

  

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References:

Behrens, E. (1975) Globodera Skarbilovic, 1959, eine selbstindige Gattung in der Unterfamilie Heteroderinae Skarbilovic, 1947 (Nematoda: Heteroderidae). Vortragstagung zu
aktuellen Problemen der Phytonematologie am 29/5/1975 in Rostock. Manuskriptdruck der Vortrage. Rostock, 1975, pp.12-26.

Knoetze, R. A. Swart, R. Wentzel and L.R. Tiedt. 2017. Description of Globodera sandveldensis n. sp. (Nematoda: Heteroderidae) from South Africa. Nematology 19:805-816.

Smant, G., A. Goverse, J.P.W.G. Stokkermans, J.M. De Boer, H. (Rikus) Pomp, J.F. Zilverentant, H.A. Overmars, J. Helder, A. Schots and J. Bakker. 1997. Potato Root Diffusate-Induced Secretion of Soluble, Basic Proteins Originating from the Subventral Esophageal Glands of Potato Cyst Nematodes. Phytopathology 87:839-845.

Stone, A.R. 1973b. "Heterodera pallida." Commonwealth Institute of Helminthology Descriptions of Plant-Parasitic Nematodes, Set 2, Nos. 16-17.

Stone, A.R. (1979). Co-evolution of nematodes and plants. Symbolae Botanicae Uppsala 22, 46-61. 1997

Subbotin, S.A., Cid Del Prado Vera, I., Mundo-Ocampo, M. & Baldwin, J.G. (2011). Identification, phylogeny and phylogeography of circumfenestrate cyst nematodes (Nematoda: Heteroderidae) as inferred from analysis of ITS-rDNA. Nematology 13, 805-824. DOI: 10.1163/138855410x552661

 

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Copyright © 1999 by Howard Ferris.
Revised: November 21, 2019.