Key to Genera of Plant-feeding Nematodes

Revised: 10/06/08

1	a	Stylet absent	Not a plant feeder Go to alternate key
1	b	Stylet/spear present	Go to 2
2	a	2-part esophagus, anterior slender, posterior glandular and muscular, spear, no metacorpus with valve	Order Dorylaimida Go to 3
2	b	3-part esophagus, metacorpus with valve, slender isthmus, glandular postcorpus, stylet usually with knobs	Aphelenchina or Tylenchina Go to 7
3	a	Spear short and curved, body thick, anus almost terminal	Trichodoridae Go to 4
	b	Spear long with long extension, body long and slender	Longidoridae Go to 5
	c	Spear short and straight	Not a plant feeder Go to alternate key
4	a	Diovarial, males without caudal alae	*Trichodorus*
	b	Diovarial, males with caudal alae	*Paratrichodorus*
	c	Monovarial, males without caudal alae	*Monotrichodorus*
	d	Monovarial, males without caudal alae	*Allotrichodorus*
5	a	Spear extension with basal flanges, guiding ring near base of spear	*Xiphinema*
5	b	Spear extension without basal flanges, guiding ring near tip of spear	Go to 6
6	a	Amphid openings small and slit-like	*Longidorus*
6	b	Amphid openings wide, posterior to lips	*Paralongidorus*
7	a	DEGO in metacorpus and difficult to see; metacorpus usually nearly as large as body diameter	Suborder Aphelenchina Go to 8
7	b	DEGO in procorpus; metacorpus usually less that 75% of body width	Order Tylenchida Go to 10
8	a	Vulva with overlapping flap, vagina curved, male with small bursa at tail tip	*Bursaphelenchus*
8	b	Vulva without flap, vagina not curved	Go to 9
9	a	Female tail bluntly rounded, lateral field with 6-15 lines, male with bursa and gubernaculum	*Aphelenchus*
9	b	Female tail usually conoid and mucronate, lateral field with 3-5 lines, male without bursa or gubernaculum	*Aphelenchoides*
10	a	Head with setae, no plant feeders	Go to 74
10	b	Head without setae, mainly plant feeders	Go to 11
11	a	Metacorpus absent or reduced, no valve.	*Nothanguina, Nothotylenchus*
11	b	Metacorpus with valve	Go to 12
12	a	Mature females greatly enlarged (pear-shaped, kidney-shaped), embedded or attached to plant roots, or free in soil as cysts	Go to 13
12	b	Mature females vermiform, slender to slightly swollen	Go to 24
13	a	Mature female body elongate-saccate or kidney shape and not hardened into a cyst	Go to 14
13	b	Mature female body pear-, lemon-shaped or spherical, may be hardened into a cyst	Go to 19
14	a	Female diovarial	*Rotylenchulus*
14	b	Female monovarial	Go to 15
15	a	Excretory pore in esophageal region, near nerve ring	Go to 16
15	b	Excretory pore posterior to nerve ring	Go to 17
16	a	Mature female subspherical, may have a protruding vulva, cuticle marked with coarse reticulate pattern	*Sphaeronema*
16	b	Mature female a thick spiral, without protruding vulva	*Trophonema*
17	a	Lip region elevated in females and juveniles	*Trophotylenchulus*
17	b	Lip region not elevated, continuous with body contour	Go to 18
18	a	Excretory pore in posterior third of body, near vulva	*Tylenchulus*
18	b	Excretory pore near basal region of esophagus	*Nacobbus*
19	a	Females with perineal pattern, excretory pore close to level of stylet, lip region with 2 lateral lips and 4 smaller sublateral lips, weak head frame, J2 stylet ≤20μm, host roots usually galled	*Meloidogyne*
19	b	Females without perineal pattern, excretory pore posterior to metacorpus, lip region with 2 lateral lips smaller than 4 sublateral lips, J2 stylet ≥20μm, host roots not galled	Go to 20
20	a	V > 50% but well anterior to anus, cuticle striated	*Meloidodera*
20	b	Vulva terminal or subterminal, cuticle striated or lace-patterned	Go to 21
21	a	Cuticle striated	*Cryphodera*
21	b	Cuticle lace-patterned	Go to 22
22	a	Female body hardens to cyst, vulva terminal or on a terminal vulval cone, anus dorsal to vulva	Go to 23
	b	Female body does not harden to cyst, vulva and anus on terminal prominence	*Atalodera*
	c	Female body does not harden to cyst, vulva sunken into terminal vulval cone with anus on upper side of dorsal vulva lip, J2 stylet >38μm	*Sarisodera*
23	a	Cysts generally lemon-shaped, vulva on terminal vulval cone with fenestration, bullae present or absent, J2 stylet <30μm	*Heterodera*
23	b	Cyst spherical or subspherical, bullae absent, J2 with 5 lines in lateral field	*Globodera*
24	a	c' ≥ 6, filiform with pointed or clavate terminus	Go to 25
24	b	c' generally < 6, but if longer it is cylindroid rather than filiform	Go to 29
25	a	Female diovarial	Go to 26
25	b	Female monovarial	Go to 27
26	a	Stylet without knobs, no cephalic sclerotization, tail filiform, usually with clavate terminus	Go to 70
26	b	Stylet with knobs, heavy cephalic sclerotization, tail filiform with pointed terminus	*Brachydorus*
27	a	Esophagus criconematoid with swollen procorpus continuous with metacorpus, cuticle thick and coarsely striated	*Caloosia*
27	b	Esophagus tylenchoid, procorpus not swollen,, cuticle thin, not coarsely striated	Go to 71
28	a	Blank couplet
28	b	Blank couplet
29	a	Monovarial, vulva in posterior third of body	Go to 30
	b	Monovarial, V near 50%, lip region conical and not striated, female tail tip rounded, cuticle of tail swollen	*Trophurus*
	c	Diovarial, V near 50%	Go to 45
30	a	Procorpus not swollen and combined into metacorpus or, if swollen, offset from metacorpus by a constriction	Go to 31
30	b	Procorpus swollen and continuous with metacorpus	Superfamily Criconematoidea Go to 38
31	a	Stylet delicate, ≤15μm, tail acute or subacute	Go to 32
31	b	Stylet strong, >15μm, tail tapering or bluntly rounded	Go to 34
32	a	Ovary with oocytes in one or two rows, not arranged around central rachis, mature female slender to stout	Go to 33
32	b	Ovary with multiple rows of oocytes arranged around central rachis, mature female usually obese, in seed, leaf or flower galls	*Anguina*
33	a	Ovary with one or two flexures, female moderately stout, in root galls of Graminae	*Subanguina*
33	b	Ovary outstretched, female slender, in bulbs, stems, leaves, tubers	*Ditylenchus*
34	a	s≥1.5, c' generally ≤1.5	*Rotylenchoides*
34	b	s<1.5, c' >1.5	Go to 35
35	a	Esophagus overlaps intestine ventrally	*Pratylenchus*
35	b	Esophagus overlaps intestine dorsally	Go to 36
36	a	Lip region low, generally rounded, stylet knobs flattened anteriorly, sexual dimorphism	*Radopholoides*
36	b	Lip region high, conoid, stylet knobs sloping anteriorly or indented, males present or absent	Go to 37
37	a	Female body swollen, stylet knobs sloping anteriorly, sexual dimorphism	*Acontylus*
37	b	Female body slender, stylet knobs tapering anteriorly to a dentate tip, males absent	*Hoplotylus*
38	a	Mature female without extra cuticle or sheath	Go to 39
38	b	Mature female with extra cuticle or sheath	Go to 41
39	a	Cuticle with prominent retrorse striations	Go to 40
39	b	Cuticle without prominent retrorse striations	Go to 42
40	a	Cuticular striations of female with spines, scales, plates or stalks on posterior margins	*Criconema*
40	b	Cuticular striations of female with smooth or crenate on posterior margins	*Criconemoides*
41	a	Stylet knobs rounded, sloping anteriorly, usually >200 striations on cuticle	*Hemicriconemoides*
41	b	Stylet knobs anchor-shaped, usually <200 striations on cuticle	*Hemicycliophora*
42	a	Cuticular striations of female with membranous structures on posterior margins	*Bakernema*
42	b	Cuticular striations of female without membranous structures on posterior margins	Go to 43
43	a	Cuticle of female with minute tubercles	*Cacopaurus*
43	b	Cuticle of female without minute tubercles	Go to 44
44	a	Female stylet ≤36μm	*Paratylenchus*
44	b	Female stylet 45-120μm	*Gracilacus*
45	a	s≥2.5	Go to 46
45	b	s generally <2.5	Go to 50
46	a	Esophageal glands not enclosed in a bulb, usually unequal in length, overlapping intestine	Go to 47
46	b	Esophageal glands enclosed in a bulb, usually butting intestine	Go to 48
47	a	Average adult body length ≥1.75mm	*Belonolaimus*
47	b	Average adult body length <1.75mm	Go to 49
48	a	Lip region continuous with body contour	*Macrotrophurus*
48	b	Lip region offset from body contour by a constriction	*Dolichodorus*
49	a	Lateral field with 5 lines	*Morulaimus*
49	b	Lateral field with 3 lines	*Carphodorus*
50	a	Phasmids absent	*Aphasmatylenchus*
50	b	Phasmids present	Go to 51
51	a	c'<1.5	Go to 62
51	b	c'≥1.5	Go to 52
52	a	Esophageal glands usually unequal in length, overlapping intestine dorsally or lateroventrally	Go to 53
52	b	Esophageal glands enclosed in a bulb or equal in length, usually butting intestine	Go to 60
53	a	Weak to moderate cephalic framework, female head not low or flattened	Go to 54
53	b	Well-developed cephalic framework, female head low , rounded or flattened	Go to 57
54	a	Well-developed stylet, lateral field with 5 lines	Go to 55
54	b	Stylet slender with diverging knobs, lateral field with 4 lines	*Trichotylenchus*
55	a	Female tail cylindroid with rounded terminus	Go to 56
55	b	Female tail elongate-conoid with blunt terminus	*Telotylenchus*
56	a	Stylet cone asymmetrical, c' around 2, tail with broadly rounded terminus	*Histotylenchus*
56	b	Stylet cone symmetrical, female tail with broadly rounded to bulbous terminus and strongly thickened cuticle	*Telotylenchoides*
57	a	Esophagus overlapping intestine dorsally	Go to 58
57	b	Esophagus overlapping intestine ventrally	Go to 59
58	a	Short overlap, no obvious sexual dimorphism	*Pratylenchoides*
58	b	Long overlap, distinct sexual dimorphism	*Radopholus*
59	a	Tail tip mucronate	*Hirschmanniella*
59	b	Tail tip not mucronate	*Zygotylenchus*
60	a	Lateral field with 4 lines, female tail not acute	Go to 61
60	b	Lateral field with 6 lines, female tail acute or subacute	*Merlinius*
61	a	Female tail conoid with terminus bluntly rounded	*Tylenchorhynchus*
61	b	Female tail cylindroid, tail with broadly rounded terminus and thick cuticle	*Paratrophurus*
62	a	Phasmids small, pore-like	Go to 63
62	b	Phasmids enlarged	Go to 64
63	a	Esophagus overlapping intestine dorsally and laterally, lip region with or without striation, DEGO <0.25 of stylet length behind knobs	*Rotylenchus*
63	b	Esophagus overlapping intestine ventrally, lip region without longitudinal striation, DEGO ≥0.25 of stylet length behind knobs	*Helicotylenchus*
64	a	Both phasmids posterior to vulva	Go to 65
64	b	One phasmid anterior and one posterior to vulva	Go to 66
65	a	Phasmids nearly opposite each other in region of anus, lip region with transverse striations	*Scutellonema*
65	b	Phasmids anterior to anus, not opposite each other, lip region without striations	*Peltamigratus*
66	a	Stylet knobs with anterior projections, ≤5 lines in lateral field, lateral field areolated throughout length	*Hoplolaimus*
66	b	Stylet knobs rounded and without anterior projections, 5 lines in lateral field, lateral field areolated at phasmids and in anterior	*Aorolaimus*
67	a	Females diovarial	Go to 68
67	b	Females monovarial	Go to 71
68	a	Tail short, subcylindrical, rounded; stylet very long (90-110µm)	Macrotrophurus
68	b	Tail elongate, attenuated; stylet < 20µm	Go to 69
69	a	Cephalic framework sclerotized; vulva with lateral membranes; male cloaca with hypoptygma	Antarctenchus
69	b	Cephalic framework not sclerotized; vulva withithout lateral membranes; male cloaca without hypoptygma	Go to 70
70	a	Head high, amphidial slit obvious; metacorpus posterior to middle of esophagus	Psilenchus
70	b	Head low, amphidial slit indistinct; metacorpus anterior to middle of esophagus	Atetylenchus
71	a	Stylet very long (76-104µm)	Tylodorus
	b	Stylet long (38-52µm)	Epicharinema
	c	Stylet moderate (22-34µm)	Go to 72
	d	Stylet short (<22µm)	Go to 73
72	a	Cuticle with longitudinal ridges	Campbellenchus
72	b	Cuticle without longitudinal ridges	Gracilancea
73	a	Head with setae	Go to 74
73	b	Head without setae	Go to 75
74	a	Vulva covered by longitudinal flap; male without caudal alae; male cloaca with hypoptygma	Atylenchus
74	b	Vulva with lateral flaps; male with caudal alae; male cloaca raised	Eutylenchus
75	a	Cuticle with longitudinal ridges	Go to 76
75	b	Cuticle without longitudinal ridges	Go to 80
76	a	Cone about 1/3 of stylet length	Go to 77
76	b	Cone almost 1/2 of stylet length	Go to 79
77	a	Transverse striations not visible through longitudinal ridges	Basirienchus
77	b	Transverse striations and longitudinal ridges form block (tessellate) pattern; lateral field with 4 lines	Go to 78
78	a	Lip region with 2-3 striations, stylet without knobs	Neothada
78	b	Lip region with 6-7 striations, stylet without knobs	Basirienchus
79	a	Vulva covered by longitudinal flap; stylet 17-19µm	Pleurotylenchus
79	b	Vulva with lateral flaps; stylet <81µm	Coslenchus
80	a	Cone about 1/3 of stylet length	Go to 81
80	b	Cone almost 1/2 of stylet length	Go to 94
81	a	Head high, with distinct lateral amphid slits	Go to 82
81	b	Head variously shaped, amphid slit longitudinal	Go to 85
82	a	Female body ventrally curved or spiral; female with offset spermatheca and oocytes in multiple rows	Boleodorus
82	b	Female body straight; oocytes not in multiple rows	Go to 83
83	a	Tail bent or hook-shaped near tip	Basirienchus
83	b	Tail more or less straight	Go to 84
84	a	Stylet without knobs, anterior part with wide lumen	Neopsilenchus
84	b	Stylet with or without knobs, anterior conical with narrow lumen	Basiria
85	a	Head with disc-like structure	Go to 86
85	b	Head with smooth contour	Go to 88
86	a	Head with small disc	Go to 87
86	b	Head with large dome-shaped structure	Cucullitylenchus
87	a	Very slender (a=62-76); caudal alae concave posteriorly	Mitranema
87	b	Less slender; caudal alae rounded	Filenchus
88	a	Very slender (a=60-180); caudal alae lobed	Go to 89
88	b	Body width variable; caudal alae rounded if present	Go to 90
89	a	Head quadrangular; pore-like amphid apertures; body constricted after vulva	Ecphyadophora
89	b	Head flattened; long amphid apertures; body not constricted after vulva	Ecphyadophoroides
90	a	Cuticle deeply incised	Go to 91
90	b	Cuticle not deeply incised	Go to 92
91	a	Head quadrangular; body striations with zigzag pattern; male without caudal alae	Miculenchus
91	b	Head flattened; male with caudal alae	Malenchus
92	a	Very slender; indistinct striation; head very flat; long, sinuous amphid aperture	Lelenchus
92	b	Larger body diameter; distinct striation; head quadrangular; aperture not sinuous	Go to 93
93	a	Head high with longitudinal amphid apertures lateral; clavate stylet knobs; DEGO > 1/2 stylet length behind knobs	Irantylenchus
93	b	Head quadrangular; distinct striation; round stylet knobs; DEGO < 1/2 stylet length behind knobs	Filenchus
94	a	Vulva with lateral flaps	Go to 95
94	b	Vulva without flaps	Go to 96
95	a	Lateral field with 2 lines; vagina thin; post-vulval sac short	Allotylenchus
	b	Lateral field with 3 lines; vagina thickened; post-vulval sac short	Aglenchus
	c	Lateral field with 4-6 lines; vagina not thickened; post-vulval sac long	Cephalenchus
96	a	Lateral field and striations inconspicuous; caudal alae very small	Polenchus
96	b	Lateral field and striations distinct; caudal alae distinct	Tylenchus

De Man Formula Definitions (a,b,c,c',V,s, etc.)

Sources:

Adapted and compiled with slight modification from:

Mai, W.F. and P.G. Mullin (with H.H. Lyon and K. Loeffler) 1996. Plant-Parasitic Nematodes: A pictorial key to genera. Cornell University Press, Ithaca, NY 277p.

Geraert, E. and Raski, D.J. 1987. A reappraisal of Tylenchina (Nemata) 3. The family Tylenchidae Örley, 1980. Revue de Nematologie 10:143-161.

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