| Golden nematode |
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| Globodera rostochiensis |
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Plant hosts
- Major hosts: Lycopersicon esculentum (tomato), Solanum melongena (aubergine), Solanum tuberosum (potato)
- Minor hosts: Datura stramonium (jimsonweed), Lycopersicon pimpinellifolium (currant tomato), Oxalis tuberosa (oca), Solanum (nightshade), Solanum aviculare (kangaroo apple), Solanum gilo (gilo), Solanum indicum, Solanum marginatum (white-edged nightshade), Solanum mauritianum (tree tobacco), Solanum nigrum (black nightshade), Solanum quitoense (Narangillo), Solanum sarrachoides (green nightshade (UK))
To view larger picture click on image.
Image provided by Ulrich Zunke, University of Hamburg, Germany.
Means of movement and dispersal
Plant parts liable to carry the pest in trade and transport:
- Bulbs, tubers, corms and rhizomes: juveniles, adults and sclerotia are born internally and externally and are visible under light microscope.
- Roots: juveniles, adults, and sclerotia are born internally and externally.
- Stems: juveniles, adults, and sclerotia are born internally and externally and are visible under light microscope.
Plant parts not known to carry the pest in trade and transport:
- Bark.
- Fruits.
- Growing medium accompanying plants.
- Flowers.
- Leaves.
- Seedlings and micropropagated plants.
- Seeds.
- Wood.
Transport pathways for long distance movement:
- Conveyances (transport Vehicles): cysts as contamination.
- Non-host plant material: cysts as contamination.
- Containers and packing: cysts as contamination.
- Soil, gravel, water, etc.: cysts in soil and dust storms
Symptoms
Potato cyst nematodes, in common with other cyst nematodes, do not cause specific symptoms of infestation. Initially, crops will display patches of poor growth and these plants may show chlorosis and wilting. When the tubers are harvested there will be a yield loss and tubers will be smaller. To be confident that these symptoms are caused by potato cyst nematodes and to give an indication of population density, soil samples must be taken or the females or cysts must be observed directly on the host roots. In heavily infested soils, plants have reduced root systems and often grow poorly due to nutrient deficiencies and to water stress. Plants may senesce prematurely as they are more susceptible to infection by fungi such as Verticillium sp. when heavily invaded by potato cyst nematodes. Direct damage to roots and the yield of tubers The infective second stage juvenile of both G. rostochiensis and G. pallida respond to environmental conditions when hatching. There is a short period of time for the second stage juvenile to locate a host root and begin the process of invasion, usually just behind the root tip. The juveniles then position themselves next to the stele within the root where, after a few hours, they will establish a feeding site (syncytium), which will become their nutrient source until their death.
If a susceptible variety of potato is planted the plants will soon show signs of attack particularly when nematode density is high. In resistant plant varieties juveniles still hatch from the cyst and invade the plant roots, but they are unable successfully to establish a feeding site or syncytium. In this situation, males are more likely to be produced than females, as males have negligible nutrient requirements compared to females. The reduction in the yield of potato tubers, depending on the cultivar grown is also related to or dependent on the plant's ability to photosynthesise efficiently, which directly influences the yield. The effects of potato cyst nematode on the plant include water stress and early senescence of the leaves. A heavily infested plant is unlikely to produce 100% ground cover with its reduced canopy of leaves. Many field studies have monitored the progression of ground cover by leaves and correlated the findings with yields (see Trudgill et al., 1998).
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