|
|
Genus Globodera
The Cyst Nematode
Most important species: G. rostochiensis and G. pallida
- limited host range and mainly found in temperate climates
- reproduce by amphimixis
- form round cysts (female body) that hardens and encloses eggs
- second most damaging nematode pathogen on crops
- 13 species identified
- primary impact on solanaceous plants(potato, tomato, eggplant, tobacco)
- typically have one generation per year(primary inoculum)
Globodera rostochiensis (potato cyst "golden nematode")
Globodera pallida (potato cyst)
Globodera tabacum (tobacco cyst)
- subspecies solanacearum
- subspecies tabacum
- subspecies virginae
Life Cycle
- J2 cuts slit in egg shell with stylet(no enzymes involved)
- J2 migrates to root zone of elongation and penetrates to vascular
cylinder
- feeding site(syncytium) is initiated and J2 molts to sedentary J3
- adult female produces 200-600 eggs that mature in the cyst
- some species produce an egg mass for spontaneous hatching
- eggs retained in cysts overwinter or survive up to 30 years(G.
pallida)
- hatching is often stimulated by hatching factors (root exhudates)
Hots parasite interactions
- intracellular migration of J2 causes necrosis mechanically and
with cellulases
- syncitia are formed in pericyle and endodermal cells by dissolution
of cell walls
- this syncytial initial is formed by the excretion of esophageal
compounds
- multinucleate cells result from the coalescence of neighboring
cells
- nuclei enlarge and cytoplasm becomes granulated
- the syncitium shows increased metabolism in response to the nematode
which is acting like a nutrient sink in the infected roots
- feeding tubes form from nematode and plant secretions in the syncitium
at the distal tip of the stylet, but are not enveloped by endoplasmic
reticulum as in root-knot feeding tubes
- a feeding plug is also formed at the point of cell wall penetration
- no galling due to the lack of hyperplasia and hypertrophy
- degradation of the syncitium results in considerably more necrosis
than root-knot
University of Nebraska-Lincoln site
for G. pallida and G. rostochiensis |
|
