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Southern Root-knot Nematode

Scientific Name
Meloidogyne incognita
Scientific Author
(Kofoid & White, 1919) Chitwood, 1949
(Nematoda: Aphelenchida: Meloidogynidae: Meloidogyninae)
Pest Status
0 Unknown
0 Unknown
NZ - Exotic
NZ - Exotic

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Diagnostic Images

Perineal Pattern - Male
Slide mounted
Zeng Zhao Landcare Research
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Diagnostic Images (5)
Diagnostic Notes

Body is pear-shaped; the posterior end is globose and the neck projects anteriorly, usually in line with the tail end. Females are usually completely embedded within plant tissue, whereas the egg masses break through and protrude from the gall. Stylet is 15-17 µm long. The stylet cone is sharply pointed and distinctly curved dorsally near its middle; the shaft is slightly wider at its base. The stylet knobs are strongly set off from the shaft; they are broadly elongate and anteriorly indented. In some specimens the indentations are so pronounced that each knob almost appears as two. The opening of the DEGO is relatively close to the base of the knobs, generally 2-4 µm.

The perineal pattern characteristically has a high dorsal arch with smooth to wavy striae. However, some patterns have a lower dorsal arch and finely spaced, wavy striae; others have indications of lateral wings and distinct forking near the lateral lines. Often some striae bend toward the vulva. Two morphological variants have been described.

M. incognita var. incognita-type of patterns are characterised by a high squarish dorsal arch with fine, wavy striae in the subdorsal sectors. Likewise, M. incognita var. acrita-type patterns have a high squarish dorsal arch, but the striae in the subdorsal sectors are not wavy and they are coarser than in M. incognita var. incognita.


The large rounded labial disk is distinctly raised above the medial lips and may be centrally concave. In some populations, the labial disk is consistently not as much rounded and raised, and is more continuous with the medial lips. The medial lips are crescent-shaped in face view and extend for some distance posteriorly onto the head region. In some populations they seem to be more elongate and extend further onto the head region. Lateral lips generally absent, although in a few populations they are well developed, and others only remnant are visible on the head region. The stylet varies in length from 23-25 µm and has a characteristic morphology. The stylet lip is bluntly rounded and flattened laterally. A ventral projection approximately 4 µm from the tip marks the posterior of the opening of the stylet lumen. The shaft is cylindrical but often narrows near the knobs which are set off from the shaft. The distance from the base of the knobs to the DEGO is relatively short, 2-4 µm.

Second-stage Juvenile

The total body length of infective 2nd-stage juveniles is 346-463 µm (405 µm), and the tail length is 42-63 µm (52 µm). The hyaline tail terminus is 6-13.5 µm (9 µm) long.

CABI CPC 2006. Measurements (After Whitehead, 1968)

20 females: L = 500-723 (609) µm; width = 331-520 (415) µm; stylet (10) = 13-16 (14) µm; width stylet base (10) = 3-5 (4) µm; dorsal oesophageal gland orifice (8) = 2-4 (3) µm behind stylet base; length median bulb (10) = 37-63 (46) µm; width median bulb (10) = 31-49 (39) µm; length median bulb valves (10) = 13-16 (14) µm; width median bulb valves (10) = 11-13 (12) µm.

14 males: L = 1108-1953 (1583) µm; a = 31.4-55.4 (46.3); length head (13) = 6.8-8.6 (7.9) µm; stylet (13) = 23.0-32.7 (25.0) µm; width stylet base (13) = 4.7-6.8 (5.8) µm; dorsal oesophageal gland orifice (4) = 1.4-2.5 (2.1) µm behind stylet base; b' (12) = 13.8-20.5 (17.4); c (13) = 97-255 (146); length median bulb (12) = 14.4-25.2 (20.0) µm; width median bulb (12) = 8.6-15.8 (11.2) µm; length median bulb valves (12) = 5.8-9.0 (7.2) µm; spicules (length of arc) (12) = 28.8-40.3 (35.2) µm; gubernaculum (7) = 9.4-13.7 (11.2) µm.

25 juveniles: L = 337-403 (371) µm; a = 24.9-31.5 (28.3); b (21) = 2.02-3.14 (2.36); b' (24) = 6.4-8.4 (7.1); length tail = 38-55 (46) µm; d = 4.0-5.6 (4.9); c = 6.9-10.6 (8.1); length body to middle of genital primordium = 212-247 (230) µm; stylet = 9.6-11.7 (10.5) µm; length median bulb (24) = 10.1-12.9 (11.3) µm; width median bulb (24) = 5.8-8.3 (7.3) µm; length median bulb valves (22) = 3.6-6.47 (5.2) µm.
More Information
Specimen Contact
MAF Plant Health & Environment Laboratory (Nematode collection held by Zeng Zhao at Landcare Research)
Zhao, Z. Q. & Crosby, T. K.
26/05/2011 06:59 AEST
Last Updated
05/07/2011 13:12 AEST
Zhao, Z. Q. & Crosby, T. K. (2011) Southern Root-knot Nematode (Meloidogyne incognita) Updated on 7/5/2011 1:12:34 PM Available online: PaDIL -
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Free for use under the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)