Meloidogyne decalineata (African coffee root-knot nematode)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Natural enemies
- Pathway Vectors
- Plant Trade
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Meloidogyne decalineata
Preferred Common Name
- African coffee root-knot nematode
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Nematoda
- Family: Meloidogynidae
- Genus: Meloidogyne
- Species: Meloidogyne decalineata
Notes on Taxonomy and NomenclatureTop of page The nature of the morphology of Meloidogyne is such that differences between species are generally very small (Jepson, 1987). The greatest differences occur in the species which are fairly host specific and have limited distributions, while those species which are most common and widespread are more difficult to distinguish. The amount of variety in different morphological features is itself variable, large variation occurs in features such as body size and female perineal patterns while, for example, stylet and second stage juvenile tail morphology are more stable. It is clear that certain features are influenced by the host and environmental conditions. No single morphological feature can be used to distinguish all Meloidogyne species, likewise, no single life-history stage can be used for identification. That most nematologists are familiar only with the most common species can lead to assumptions in the identification of unknown species. Only familiarity with the entire genus and a well defined procedure can achieve unprejudiced identification.
DescriptionTop of page Description (after Whitehead, 1968)
Females. Body pyroid, posterior end without or with very slight protuberance; head with two annules behind head-cap, basal annule of head deeply marked off; head skeleton fairly characteristic; spear knobs drawn out laterally with rounded or backwardly sloping anterior margins; excretory pore 20-50 annules behind head, i.e. from about level of the dorsal oesophageal gland duct orifice to just in front of median bulb; posterior cuticular pattern with striae fairly close and evenly spaced, often broken, especially at sides of pattern, distinct tail whorl and vulva, rudimentary lateral field in some patterns, occasionally minute disordered striae within field, phasmids close to tail terminus, cuticle often folded in ventral region of pattern.
Males. Head not offset, in lateral view fairly low, truncated cone shape with small head-cap followed by very short first annule and longer second annule which may be very faintly subdivided. In ventral view the head-cap is small, separated by amphid openings from lateral head sectors and bearing one or two faintly separated annules; head framework thin; anterior cephalid on second body annule, posterior cephalid three or four annules behind base of relaxed stylet; stylet knobs laterally rounded with back sloped anterior margins or drawn out somewhat laterally; oesophago-intestinal junction about half length of median bulb behind median bulb; posterior oesophageal region a long, narrow glandular lobe running mostly ventral to intestine; hemizonid about two body annules long 73 or 81 annules behind head and two or three annules in front of excretory pore; lateral field arising about level of base of relaxed stylet, width about one-seventh body width mid-body, marked by ten evenly spaced incisures, the outermost crenate, the number of incisures reducing to one or two in vicinity of tail and extending virtually to tail terminus; dereids and phasmids not seen; annules extend to tail terminus, tail somewhat rostrate; one testis; spicules with large, thin walled, offset heads, shaft thicker walled, blades thick walled, tapering to subacute termini, gubernaculum crescentic.
Larvae. Head high, slightly inflated truncated cone shape, its base often slightly wider than first body annule; three or four annules on head sectors, behind small, circular, head-cap. Stylet blade longer than shaft with rounded, offset, knobs occasionally with flattened anterior margins. Hemizonid two to four annules long opposite posterior end of isthmus and, where visible excretory pore lying immediately behind hemizonid; posterior oesophageal region overlaps intestine ventrally; lateral field with four main incisures and often three subsidiary incisures between them, also three innermost incisures of lateral field may appear as double lines; two primary outer bands of lateral field fairly regularly cross-striated, inner band plain; tail tapering smoothly or irregularly to subacute terminus with fine annulation to just before the last 'section' of the tail; rectum not inflated.
Females (n=20). L = 819±133 (649-1041) µm; stylet = 14 (12-17) µm; width stylet base = 3 (3-4) µm; dorsal oesophageal gland orifice = 4 (4-6) µm behind stylet base; length median bulb = 43 (34-49) µm; length median bulb valves = 12 (0-14) µm.
Males (n=20): L = 1630-1700 µm; stylet = 19-20 µm; dorsal oesophageal gland orifice = 4 µm behind stylet base; length median bulb = 20-25 µm; width median bulb = 14µm; length of median bulb valves = 12 µm; length head = 5-6.5 µm; width head = 10.5 µm; spicules (length of arc) = 33-37 µm; gubernaculum = 7 µm.
Larvae (n=25). L = 543±24 (471-573) µm; length tail = 48±2 (44-52) µm; length body to middle of genital primordium = 368±17 (321-393) µm; stylet = 12.4±0.68 (10.7-13.7) µm; length median bulb = 13.8±0.90 (11.5-15.5); width median bulb = 7.9±0.69 (6.1-9.0); length median bulb valves = 5.9±0.40 (5.0-6.8).
Eggs (unembryonated) (n=6). 118±9.5 (106-130) µm.
DistributionTop of page M. decalineata is a localised parasite of arabica coffee in Tanzania, found along the equatorial coffee belt occurring at an altitude of 900-2000 m. On Kilimanjaro, where Meloidogyne spp. were found infesting 50% of coffee trees, 25% of plants sampled were found to be infested with M. decalineata, and in the West Usambara Mountains, where infestation with Meloidogyne spp. was 60%, 12% of plants sampled were infested with M. decalineata (Whitehead, 1969).
It has also been recorded attacking the roots of young Coffea arabica cv. typica and C. canephora plants in a nursery on Sáo Tomé Island, Africa (Lordello and Fazuoli, 1980).
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.
Risk of IntroductionTop of page Coffee is a transplanted crop so there is always the possibility of spreading the nematode on infested planting material. M. decalineata was found attacking young coffee plants in a nursery (Lordello and Fazuoli, 1980) and it is thought to be the cause of poor development, yellow leaves and root galls in the field. In Tanzania the main cause of concern is the introduction, by coffee transplantation, of M. decalineata into nematode-free southern coffee growing areas.
HabitatTop of page Found in the roots of coffee plants and the surrounding soil.
Hosts/Species AffectedTop of page Meloidogyne decalineata has to date been recorded only on Coffea arabica, C. arabica cv. tipica and C. canephora.
Host Plants and Other Plants AffectedTop of page
Growth StagesTop of page Flowering stage, Fruiting stage, Seedling stage, Vegetative growing stage
SymptomsTop of page In Africa, M. decalineata is found on coffee together with other Meloidogyne spp. which are collectively called the 'African coffee root-knot nematodes'. These nematodes cause galling or knotting of the fine tertiary lateral or feeder roots (Bridge, 1984). The galls are typically rounded, occurring on the root tips, but they are also occasionally elongate along the roots behind the tip. On seriously infested roots they are observed as a mass of fine, bead-like structures along the main laterals, 1-3 mm in size. The nematodes will debilitate the plant and although they cause malformation and blinding of the roots, they have not been shown to cause necrosis or root destruction. Infected coffee seedlings are stunted, chlorotic and are often killed as a direct result of nematodes.
On the island of Sáo Tomé, M. decalineata was found infesting young coffee plants in a nursery (Lordello and Fazuoli, 1980) and was thought to be the cause of poor development, yellow leaves and root galls on trees grown in the infested field.
List of Symptoms/SignsTop of page
|Growing point / dwarfing; stunting|
|Leaves / yellowed or dead|
|Roots / galls along length|
|Roots / stubby roots|
|Roots / swollen roots|
|Whole plant / discoloration|
|Whole plant / dwarfing|
|Whole plant / plant dead; dieback|
Biology and EcologyTop of page M. decalineata usually causes small galls from 1-5 mm in diameter (Campos et al., 1990). African coffee-root nematode galls are typically rounded, occurring at the root tips, but occasionally elongate along the roots behind the tip and occurring on roots to a depth of at least 95 cm, which is considerably deeper than is found with other species of root-knot. Although the nematodes cause gross malformation and blinding of the roots, no necrosis or destruction of roots has been observed (Bridge, 1984). Each gall may contain many female nematodes and eggs. No further details of life-history have at present been published.
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
Pathway VectorsTop of page
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Growing medium accompanying plants||adults; eggs; juveniles||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Roots||adults; eggs; juveniles||Yes||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Seedlings/Micropropagated plants||adults; eggs; juveniles||Yes||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Plant parts not known to carry the pest in trade/transport|
|Fruits (inc. pods)|
|Stems (above ground)/Shoots/Trunks/Branches|
|True seeds (inc. grain)|
ImpactTop of page Although the African coffee root-knot nematodes have been known in Tanzania for many years there is no information available on the actual yield losses caused by these pests. It is clear that mature coffee trees exhibit a certain amount of tolerance to the nematodes (Bridge, 1984) and infested plants are able to survive in optimal growing conditions even though growth and yield will be affected. On the basis of figures with similar nematodes from other coffee growing countries, particularly in South America, and the amount of root damage caused by the nematodes in Tanzania, it is estimated that yield losses of severely infested trees will be in the region of 20% in optimum conditions with the percentage loss increasing under adverse conditions to the point of non-productivity. The stress to which trees are subjected because of nematode damage will also cause premature fruit drop, twig dieback and defoliation, nutrient deficiency symptoms and stunted growth.
Detection and InspectionTop of page In an advanced infestation galls will be present on the roots. If no galls are present and infestation is suspected, observations of developing larval stages and females within root tissue can be made by staining roots in lactoglycerol plus 0.05% acid fuchsin (Bridge et al., 1982).
Males and infective juveniles (j2s) can be extracted from soil surrounding the roots of infested plants by a modification of the Baermann funnel method (Hooper, 1990) or infested roots incubated at room temperature to recover juveniles and males (Whitehead, 1969).
Similarities to Other Species/ConditionsTop of page The root-knot nematodes (Meloidogyne spp.) are closely related to the cyst nematodes (Heterodera, Globodera, etc.) in that they possess a swollen sedentary female and the larval stages develop in a similar manner within the roots. The genera can be separated in the larval stages. In the j2 by a slender body with no noticeable neck constriction, a slender stylet <19 µm) and the hyaline portion of the tail starting near the tail tip in Meloidogyne, as opposed to an offset head, stronger stylet and head skeleton, and a longer hyaline tail region in the heteroderids, in the j3-j4 by the retention of the j2 tail spike in Meloidogyne, not present in the heteroderids. In the female the genus can be distinguished by the position of the excretory pore being forward of the median bulb in Meloidogyne.
The African coffee-root nematodes incite the formation of small spherical or oval galls along and at the tips of the roots. Eggs are laid into a gelatinous matrix and no egg-filled cyst is formed from the female as can be seen in the heteroderids and M. acronea. M. decalineata can be distinguished from other Meloidogyne spp. by the characteristic perineal pattern of the female and ten lateral line incisures in the male.
Prevention and ControlTop of page It was recommended that soil sterilization techniques should be standard procedure in nurseries in Tanzania so that nematode-free planting material could be given to farmers (Bridge, 1984).
ReferencesTop of page
Bridge J; Page SLJ; Jordan SM, 1982. An improved method for staining nematodes in roots. Rothamsted Report for 1981, Part 1. Harpenden, UK: Rothamsted Experimental Station.
Campos VP; Sivapalan P; Gnanapragasam NC, 1990. Nematode parasites of coffee, cocoa and tea. In: Luc M, Sikora RA, Bridge J, eds. Plant Parasitic Nematodes in Subtropical and Tropical Agriculture. Wallingford, UK: CAB International, 387-430.
Hooper DJ, 1990. Extraction and processing of plant and soil nematodes. In: Luc M, Sikora RA, Bridge J, eds. Plant Parasitic Nematodes in Subtropical and Tropical Agriculture. Wallingford, UK: CAB International, 45-68.
Swai IS, 1982. Root-knot nematodes, Meloidogyne species, in Tanzania. Proceedings of the 3rd Research Planning Conference on root-knot nematodes, Meloidogyne spp., Regions IV and V, 16-20 November 1981, (International Meloidogyne Project). Ibadan, Nigeria: International Institute of Tropical Agriculture, 28-30.
Whitehead AG, 1969. The distribution of root-knot nematodes (Meloidogyne spp.) in tropical Africa. Nematologica, 15:315-333.
Distribution MapsTop of page
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