Key to Genera of Plant-feeding Nematodes

Revised: 03/10/20

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	Sub-Order 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 females, males without caudal alae	*Trichodorus*
	b	Diovarial females, males with caudal alae	*Paratrichodorus*
	c	Monovarial females, males without caudal alae	*Monotrichodorus*
	d	Monovarial females, 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	Superfamily Aphelenchoidea Go to 8
7	b	DEGO in procorpus; metacorpus usually less that 75% of body width	Superfamily Criconematoidea or Tylenchoidea 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 < 20 µm, 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 > 20 µm, 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 >38 µm	*Sarisodera*
23	a	Cysts generally lemon-shaped, vulva on terminal vulval cone with fenestration, bullae present or absent, J2 stylet <30 µm	*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 28
28	a	Esophagus terminating in a bulb that abuts the intestine; non-overlapping	Go to 67
28	b	Esophageal postcorpus glandular region slightly to distinctly overlapping intestine	Go to 29
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, ≤ 15 µm, tail acute or subacute	Go to 32
31	b	Stylet strong, >15 µm, 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 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 ≤36 µm	*Paratylenchus*
44	b	Female stylet 45-120 µm	*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 (90-110 µm)	Macrotrophurus
68	b	Tail elongate, attenuated; stylet < 20 µm	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 (76-104 µm)	Tylodorus
	b	Stylet long (38-52 µm)	Epicharinema
	c	Stylet moderate (22-34 µm)	Go to 72
	d	Stylet short (<22 µm)	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 17-19 µm	Pleurotylenchus
79	b	Vulva with lateral flaps; stylet < 15 µm	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.

This key represents an effort to combine the key of Mai and Mullin with that of Geraert and Raski. Any resulting errors in characteristics or navigation are the fault of Howard Ferris, not of the original authors. Please bring inconsistencies and inaccuracies to my attention: hferris@ucdavis.edu

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