Radopholus similis
| Burrowing nematode | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Secernentea |
| Subclass: | Diplogasteria |
| Order: | Tylenchida |
| Family: | Pratylenchidae |
| Genus: | Radopholus |
| Species: | R. similis |
| Binomial name | |
| Radopholus similis (Cobb, 1893) Thorne, 1949 |
|
Burrowing nematode or Banana-root nematode (Radopholus similis) is an important parasite of fruit, vegetable, and other crops. It is an especially important pest of bananas and citrus, but it will also attack coconut, avocado, coffee, sugarcane, and assorted other types of grasses and ornamentals. It is a migratory endoparasite of roots. The nematode causes a lesion on the plant's root that forms a canker, and the plant suffers from malnutrition while the nematode completes its life cycle within the root.
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[edit] History and significance
First described by Nathan A. Cobb in necrotic tissue of the roots of Musa sp in 1891, Radopholus similis (Burrowing nematode) is one of the most important root pathogens attacking bananas [1]. This nematode is widespread and can cause yield losses of up to 30-60% in many countries [2].
[edit] Distribution
Widespread in most banana-growing regions of the world and present in glasshouses in temperate areas such as: Asia, Africa, North America, Central America and Caribbean, South America and Oceania [1].
[edit] Morphology
All nematode stages are vermiform. Adult males and females are different in appearance (sexual dimorphism), the males having poorly developed stylets and a knob-like head caused by an elevated, constricted lip region. Both males and females have long, tapered tails with rounded or indented ends. The male has a sharp, curved spicule enclosed in a bursa, or sac. Females are between 550 and 880 µm (0.55 to 0.88 mm) in length and about 24 µm in diameter, with well-developed stylets 16 to 21 µm (average 18 µm) long. Males are smaller than females, 500 to 600 µm in length [5].
[edit] Life cycle
Radopholus similis is a migratory endoparasitic nematode which completes its life-cycle in about 21 days at 25ºC in the root corm tissues [4]. Females and juvenile stages both attack and enter host roots, especially near the tip of the roots. Males with their weak stylets do not feed. Females lays an average of four to 2-6 eggs each day [5].
[edit] Host parasite relationship
The disease caused by R. similis is called toppling or blackhead disease [3]. As the nematodes feed they destroy anchor roots and make banana plants susceptible to toppling. Furthermore, roots damaged by nematodes cannot supply plants with needed water and nutrients, resulting in reduction of plant growth and development [4].
[edit] Management
Management of R. similis consist in reduce nematode populations in the soil before planting, for example using soil fumigation, removing host and doing rotation with non-host crops and also planting cover crops such as Crotalaria or Tagetes. Furthermore, before planting pared the rhizomes in order to remove dark spots (infections), then soak them in hot water (125ºF) for 20 minutes. Although those practices can reduce nematodes population, plants from tissue culture raised in a disease-free nursery are the best option [4].
[edit] References
1. O’Bannon, J.H (1977) Worldwide dissemination of Radopholus similis and its importance in crop production. Journal of Nematology 9, 16-25.
2. Banana Nematodes, Pests and Disease of American Samoa, number 9. American Samoa Community College Community & Natural Resources Cooperative Research & Extension, 2004.
3. M. Luc, R.A., Sikora. Plant Parasitic Nematodes in Subtropical an Tropical Agriculture, 1990.
4. J.L. Sarah, J. Pinochet and J. Stanton. The Burrowing nematode of bananas, Radopholus similis Cobb, 1913. Musa Pest Fact Sheet nº. 1.
5. http://www.apsnet.org/education/LessonsPlantPath/BurrowingNematode/pathbio.htm
