Identification of Meloidogyne Species on the Basis of Head

cultures were increased in a growth chamber at 15 C. No galling was observed on oat, rescue, or tomato, but these cultures were kept in the greenhouse and thus may have been grown at unsuitable tempera- tures.

L I T E R A T U R E CITED

I. Eroshenko, A. S. 1978. (A new species of Meloidodera [Nematoda, Heteroder idae] f rom the Pr imorsk territory.) Parazitologiya 12:456-459 (In Russian) .

2. Jenkins , W, R. 1964. A rap id centr i fugal- f lotation t echn ique for separa t ing nema todes f rom soil. P lan t Dis. Rep. 48:692.

3. Mulvey, R. H., and R. V. Anderson . 1980. Descr ipt ion and re la t ionships of a new root -knot nematode , Meloidogyne sewelli n. sp. (Nematoda : Meloidogynidae) f rom Canada and a new hos t record for the genus. Can, J. Zool. 58-1551-1556.

4. Robbins , R. T . 1978. A new Ata loder inae (Nematoda: Heteroder idae) , T hecave rmi cu l a t u s gracil i lancea n. gen., n. sp. J. Nemato l . 10:250-254.

Aleutian Heteroderoidea: Bernard 513

5. Seinhorst , J. W. 1959. A rap id m e t h o d for the t ransfer of nema todes f rom fixative to anhy- drous glycerin. Nemato logica 4:67-69.

6. Taylor , A. L., and J. N. Sasser. 1978. Biology, ident if icat ion and control of roo t -knot nema todes (Meloidogyne species). N o r t h Carol ina State Uni- versity, U.S.A,I.D.

7. T r i a n t a p h y l l o u , A. C. 1979. Cytogenetics of root -knot nematodes . Pp. 85-109 in F. Lamberti and C. E. Tay lor , eds. Roo t -kno t nema todes (Mcloidogyne species). Systematics, biology and control. New York: Academic Press,

8. W hi t ehead , A. G. 1968. T a x o n o m y of Melo idogyne (Nematodea : Heteroder idae) wi th de- script ions of four new species. T rans . Zool. Soc. Loud. 31:263-401.

9. Wouts , W. M. 1973. A revision of the fami ly Hete roder idae (Nematoda: Tylenchoidea) . II. T h e subfami ly Meloidoder inae . Nemato logica 19:218- 235.

10. Young, L. D. 1975. A Meloidogyne sp. on Amer ican beachgrass in N o r t h Carol ina. U n p u b - l ished M.S. thesis. Nor th Carol ina State Univers i ty .

11. Young, L. D., and L. T . Lucas. 1977. Hosts of Meloidogyne sp. on Amer i can beachgrass. P l a n t Dis. Rep. 61:776-777.

Identification of Meloidogyne Species on the Basis of Head Shape and Stylet Morphology of the Male 1

J. D. Eisenback and Hedwig Hirschmann x

Abstract: Head shape and stylet morpho logy of males of 90 popu la t ions of M. arenaria, M. hapla, M. incognita, and M. javanica f rom geographic regions of the world were compared by l ight microscopy (LM). I n addi t ion, stylets of one popu l a t i on each of M. arenaria, M. incognita, and M. javanica and three different ch romosomal forms of M. hapla race A and two of race B were excised and examit ted wi th a scann ing electron microscope (SEM). Differences a m o n g species occurred in bo th head and stylet morphology . H ead morpho logy differed in size a n d shape of the head cap, a n n u l a t i o n of the head region, and width of the head region relative to the first body annu le . Differences in stylets occurred in size and shape of the cone, shaft , and knobs. All popu la t ions of M. hapla, except one, h a d s imi la r head morphology , bu t stylet morphology was different be tween cytological races A and B. Popula t ions of M. javanica var ied wi th respect to the presence of head annu la t ions . H e a d shape and stylet morpho logy of males are r e c o m m e n d e d as addi t iona l characters useful in the ident i f icat ion of root -knot nematodes . Key words: Meloidogyne arenaria, M. hapla, M. incognita, M. ]avanica, root -knot nematodes , cytological races, intersexes, s cann ing electron microscopy, t axonomy.

Identification of the four common species of root-knot nematodes--Meloidogyne

Received for publication l0 February 1981. 1Paper No. 6785 of the Journal Series of the North

Carolina Agricultural Research Service, Raleigh. North Caro- lina. This study was supported, in part, by National Sci- ence Foundation Grant DEB-7917386 to A. C. Triantaphyllou and U.S. Agency for International Development Contract to-C-t234 to J. N. Sasser.

"-Research Associate and Professor, respectively, Depart- ment of Plant Pathology, North Carolina State University, Raleigh, NC 27650. We thank Dr. J. N. Sasser, Department of Plant Pathology, North Carolina State University. for conducting host differential tests and Dr. A. C. Tri- antaphyllou, Department of Genetics, North Carolina State University, for providing cytological information.

arenaria (Neal) Chitwood, M. incognito (Kofoid and White) Chitwood, M. ]avanica (Treub) Chitwood, and M. hapla Chitwood --is often difficult and time consuming. Various approaches to Meloidogyne taxonomy include host response (12,14,17), cytology (17,18,19), biochemistry (3,4,11), and morphology (1,2,5,6,7,8,9,12,13,15,20, 21,22). Host-response tests require adequate amounts of nematode inoculum, and the results may not be known for several weeks. Cytological and biochemical studies require

514 Journal o] Nematology, Volume 13, No. 4,

specific techniques and sophisticated equip- ment. Identification based on morphology can be rapid and practical if reliable dif- ferentiating characters can be determined. Generally, Meloidogyne species are identified by the perineal pat tern morphology of the adult female (9,10,16). In populat ions of the four common species, however, perineal patterns are variable and definite identification is not always possible (5,9,10, 12,13). Additional characters that are less variable are needed to supplement perineal pattern morphology.

In a recent scanning electron microscope (SEM) study, we reported that the head morphology of males of M. arenaria, M. incognita, M. javanica, and M. hapla was distinct for each species (7). Observed differences among species, and in M. hapIa between races, were striking. Subsequent studies revealed that some of these differences, especially in head shape, could also be detected in the light microscope (LM). When examining root-knot nematode females (8), we shouted that differences occur in stylet morphology among the four common species.

T h e present study compares by LM the head shape of males of several populat ions of each of the four common species of root- knot nematodes. It also compares by LM and SEM the morphology of stylets of males of one populat ion each of M. arenaria, M. incognita, and M. javanica and five different chromosomal populat ions of M. hapla.

MATERIALS AND M E T H O D S

Ninety populat ions of the four common root-knot nematode species from geographic regions of the world were selected from the Meloidogyne collection at Nor th Carolina State University. Th i r t een populat ions were M. arenaria; 12, M. hapla; 44, M. incognita; and 31, M. favanica. All populations were propagated on tomato (Ly- copersicon esculentum Mill. 'Rutgers') in a greenhouse maintained at 22-28 C. Each popula t ion had been characterized by its ability to reproduce on five host differ- entials (16), and many populat ions had been identified on a cytological basis. T h e populations of M. arenaria and M. incognita belonged to several host races of

October 1981

the respective species (14,16), and the populations o1: M. hapla represented the two cytological races (18).

Males were obtained by incubating washed infected root systems in a moist chamber at room temperature. T h e males were killed with hot T A F and mounted in the fixative for LM observations. Some specimens were killed, fixed, and mounted in glutaraldehyde (7) for addit ional morphological studies, and others were examined alive for comparison with fixed material. For diagnostic studies the males must be viewed in exact lateral position. Camera lucida drawings and LM photographs of the anterior body region including the stylet were made of representative populations. At least 30 specimens from each population were examined. Eight of the populations used in this study were the same populations used in previous LM and SEM observations of second-stage juveniles, males, and females (6,7,8).

Stylets of males of one popula t ion each of M. arenaria, M. incognita, and M. javanica and five different chromosomal populations of M. hapla were observed by SEM. T h e following populations were examined: M. arenaria, 351-Fla; M. incognita, 68-NC; M. iavanica, 76-GA; M. hapla race A, 6-NC, 42-Can, and 86-NC; and M. hapla race B, 48-NC and 230-Chile. T h e technique orig- inally developed for the removal of stylets of females (8) was adapted to males. Five males were transferred into a drop of 45% lactic acid on a glass coverslip. T h e specimens were cut behind the median bulb with a dental root canal file and processed for SEM observations as previously described (8). At least g0 stylets from each popula t ion were observed. Th e LM observations of the stylet morphology of all populations were compared with the SEM observations of the eight populat ions previously listed.

OBSERVATIONS

Head morphology: T h e basic head morphology of Meloidogyne males is derived from SEM and LM observations (Figs. 1, 2). Labial disc and medial lips as observed in the SEM (7) appear in the LM as a single structure, the "head cap." T h e annulations in the head region, so distinct in

ba.....__L1

s[[ff(

V

b! c

s~

sl

2

Figs. 1-2. Diagram illustrating the generalized head morphology of a male of the genus Mel- oidogyne. 1) Face view (derived from SEM) and 2) lateral view (derived from LM and SEM); ba, body annule; bc, body cavity; bp, basal plate; cf, cephalic framework; cs, cephalic sensiltum; c, cuticle; dgo, dorsal gland orifice; e, esophagus; ha, head annula- tion; hc, head cap; hr, head region; ils, inner labial sensillum; ld, labial disc; If, lateral field; 11, lateral lip; ml, medial lip; ps, prestoma; sin, somatic muscles; s, stoma; sc, stylet cone; sk, stylet knobs; sl, stylet lumen; sp, stylet protractor muscles; ss, styler shaft; v, vestibule; re, vestibule extension,

the SEM, are more difficult to observe in tile LM. Generally, the head region is in the same contour with the anterior body region, but in some specimens the diameter of the head region is larger than that of the first body annule and thus the head region appears distinctly set off. T h e anterior body region bears annules in regular iaterva!s,

Meloidogyne Male Head Shapes: Eisenback, Hirschmann 515

and the lateral field begins near the level of the stylet knobs.

Th e four common species differ in their head morphology with respect to shape and size of the head cap, presence or absence of annttlation in the head region, and the way the head region fuses with the body region. In M. arenaria (Figs. 3, 9) the head cap is low, slopes posteriorly, and is nearly as wide as the head region. Usually the head region is marked by 1-2 incomplete annulat ions and is not set off from the body region. M. incognita males (Figs. 4, 10) possess a high head cap formed by a large round labial disc that is raised above the medial lips and centrally concave. T h e head cap is as wide as tile head region. T h e head region generally bears 2-4 incomplete annulations, al though some populat ions may have com- plete annulations. T h e head region is not set off. In M. javanica (Figs. 5, 11) the head cap is high and rounded and almost as wide as the head region. T h e head region is not set off and is usually smooth, al though 5 of the 31 populat ions had 2-3 incomplete annules. T h e head shapes of males of all populations of M. hapIa race A (Figs. 6, 12) and race B (Figs. 7, 13) are similar except for one populat ion. In M. hapla the head cap is high and much narrower than the head region which lacks annulat ions and is distinctly set off from tbe body. Generally, the distance between body annulations, as well as their diameter, decreases as they near the head region. Males of populat ion 42-Can of M. hapla (Figs. 8, 14) are unique because the head cap is comparatively wider than in typical M. hapla populations and the head region is not set off from the body. Body annulations are indistinct.

Styler morphology: T h e excised stylet and attached cuticular lining of the esophagus of tile male as seen in the SEM (Fig. 15) is similar to that of the female (8) except for a few structural differences. In the male the opening of the stylet lumen is located one-fourth the length of the cone from the stylet tip, the esophageal lumen is smaller in diameter, and the triradiate lining of the smaller metacorpus pump is of tile same thickness throughout .

Differences in stylet morphology of the male as seen in LM and SEM occur in the shape of the cone, shaft, and knobs. In M.

516 Journal of Nernatology, Volume 13, No. 4, October 1981

Figs. 3-8. LM photographs of lateral view of males. 3) Meloidogyne arenaria. 4) M. incognita. 5) M. iavanica. 6) M. hapla race A. 7) M. hapla race B. 8) M. hapla race .k population 42-Can. All figures are same scale as gig. 8.

arenaria (Figs. 3, 9, 16) the styler tip is pointed and there may be a slight projec- tion on the ventral side of the cone, posterior to the orifice. T h e anter ior two-thirds of the cone gradual ly increase in width and the posterior one-third greatly increases in width. T h e shaft can be wider in the mid- dle, bu t generally remains cylindrical. T h e rounded, robust knobs gradual ly merge with the shaft. T h e stylet tip of M. incognita (Figs. 4, 10, 17) is b lun t and the anterior por t ion of the cone is blade-like. Often there is a pronounced project ion posterior to the stylet opening. T h e cylindrical shaft may narrow slightly at the junc-

tion with the knobs which are broadly elongate to round, sometimes anteriorly indented, and set off f rom the shaft. In M. javanica (Figs. 5, 11, 18) the anter ior two- thirds of tlle cone gradual ly increase in width. Styler lumen openings were found in only 7 of 30 specimens. T h e shaft is cylindrical and the styler knobs are low and wide, often anteriorly indented, and set off from the shaft. T h e styler morphology of tile M. hapla populat ions is unique for tile species but the two races have slightly different stylets. In populat ions of both races the stylet cone gradually increases in width, and the base of the cone is


t ¸ o'~1

Figs. 9-14. Line drawings of lateral view of males. 9) Meloidogyne arenaria. 10) M. incognita. 11) M. iavanica. 12) M. hapla race A. 13) M. hapla race B. 1t) M. hapla race A popula t ion 42-Can. All figures are same scale as Fig. 14.

only slightly wider than the anterior por- tion of the shaft. In populat ions of race A (Figs. 6, 8, 12, 14, 19) the shaft is wider near its junct ion with the knobs than at the junct ion with the cone, whereas in race B populations (Figs. 7, 13, 20) the shaft remains cylindrical except for a slight nar- rowing near its junct ion with the knobs. T h e rounded, set-off stylet knobs are larger in race B populations. T h e stylets of M. hapla are smaller than those of the other three common root-knot nematode species.

DISCUSSION

T h e present study of Meloidogyne males

of many populat ions from various sources around the world shows that head shape and stylet morphology are good, reasonably reliable taxonomic characters for the identification of the four common root-knot nematode species by light microscopy. We also illustrated the value of the SEM in recognizing morphological details in the LM that might otherwise be missed.

T h e populat ions of M. arenaria belonged to cytological race A and represented host races 1 and 2 (16). Although minor morphological differences were noticed among populations, certain basic characteristics are common for this species.

518 Journal of Nematology, Volume 13, No. 4,

15

/ 7

/ /i ti

/

~ o . o pm

Fig. 15. SEM photograph of an excised stylet and attached cuticular lumen lining of the esophagus of a Meloidogyne male.

October 1981

In some specimens of M. arenaria the head morphology may be similar to that of M. iavanica males, particularly if the /lead cap is high or does not slope much posteriorly. However, the two species can easily be sep- arated by stylet morphology. In M. javanica the stylet knobs are low, wide, and set off from tile shaft,, whereas in M. arenaria the knobs are rounded and gradually merge with tile shaft.

T h e populations of M. incognita belonged to host races 1, 3, and 4 (16) and included only cytological race A. All populations had similar head shape and stylet morphology. Th e styler morphology of M. incognita resembles that of M. javanica in tile LM because the uniquely shaped stylet cone of M. incognita cannot always be seen clearly; also, in some specimens the stylet knobs appear as wide as in M. javanica. These two species, however, can easily be distinguished on the basis of head morphology.

Presently, only one cytological and one host race of M. javanica are recognized. T h e head shape of all populations in this study was similar. Most populations did not have head annulations, al though 4 of tlle 26 populations examined had 2-3 head annulations. Chitwood, in his original description of M. javanica, described males with three head annulat ions (2). Future investi- gations should at tempt to correlate head annulat ion with other taxonomic characters. Fourteen populations of M. javanica had male intersexes in large proportions, whereas the remaining populations did not produce intersexes, even though many males were present. Chitwood (2) stated that true males were rare, and Triantaphyl- lou (17) has reported on intersex formation in this species. Further research should elucidate if all populations of M. javanica have the ability to produce male intersexes.

Populations of M. hapla included [our each from cytological race A and B (18). T h e populat ions of the two cytological races were similar in head shape, except for popula t ion 42 from Canada with 15 chro- mosomes. Stylet morphology of the races, however, is quite different, and individual populations can be identified according to stylet length and shape o[ stylet shaft. In his original description of M. hapla, Chit-

16 17 18 19 20

f

X b

j

Figs. 16-20. SEM p h o t o g r a p h s of exc i s ed s tylets . 16) Meloidogyne arenaria. 17) M, incognita. 18) M. javanica. 19) M. hapla race A. 20) M. hapla race B. Al l f igures a re s a m e scale as Fig. 20.

~°

g~

¢D g~

,°

o~

g~ c3

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G-x

520 Journal of Nematology, Volume 13, No.

wood (2) p o i n t e d o u t two var ie t ies based on differences in ma le s ty le t length . I n one g r o u p the males h a d sho r t stylets (17- 18 /zm), in the o t h e r l ong stylets (20 /tm). A c c o r d i n g to o u r f indings, p o p u l a t i o n s wi th shor t stylets b e l o n g to race A, p o p u l a t i o n s wi th long stylets to race B.

A c o m p a r i s o n of the s ty le t a n d a t t a c h e d cu t i cu l a r l u m e n l i n i n g of the female (8) w i th tha t of the ma le reveals some struc- t u r a l differences. I n the female the esophageal l u m e n l i n i n g of the p r o c o r p u s is th ick and the t r i r a d i a t e l i n i n g of the m e t a c o r p u s p u m p is large a n d thick. T h e thick, r i g i d edges of the l i n i n g s u p p o r t the m e t a c o r p u s p u m p , a n d the th in , f lexible i n n e r p o r t i o n s are p u l l e d a p a r t by the p u m p muscles, thus p r o d u c i n g the suc t ion r e q u i r e d for feeding . In the ma le the t r i r a d i a t e l i n i n g is t h i n t h r o u g h o u t a n d the p u m p p r o b a b l y is n o t func t iona l . Styler orifices were n o t seen in 70% of the M. javanica males w h i c h fu r t he r ind ica tes tha t males do n o t feed. T h e opening of the s tylet l u m e n in the ma le is lo- ca ted m o r e pos t e r i ad on the cone t h a n in the female.

W h e n stylets of the two sexes are com- p a r e d w i t h i n the same species (8) s im i l a r m o r p h o l o g i c a l t rends are a p p a r e n t . I n M. arenaria the s tyler is r o b u s t a n d the k n o b s g r a d u a l l y merge wi th the s ty le t shaf t in the ma le and female . In M. incognita the s tylet cone is u n i q u e l y shaped in b o t h sexes a n d the overa l l shape of the k n o b s is s imi la r , even t h o u g h the female s ty le t k n o b s are wider . I n M. iavanica the s ty le t cone is s t r a igh t and the k n o b s are sho r t and w ide a n d a n t e r i o r l y i n d e n t e d in b o t h sexes. Males a n d females of b o t h races of M. hapla have stylets w i th na r row, p o i n t e d cones a n d r o u n d e d , set off knobs . Some differences were n o t e d in the shape of the s ty le t shaf t be tween the sexes of race B. I n race B males the s tylet shaf t r e m a i n s cy l ind r i ca l t h rough- o u t and of ten na r rows n e a r the knobs , whereas in the females the shaf t is w i d e r nea r the knobs .

Prev ious ly , the va lue of males in root - k n o t n e m a t o d e t a x o n o m y has n o t been emphas ized because of the i r a p p a r e n t mor- p h o log i ca l v a r i a b i l i t y a n d scarci ty. Males , however , were n u m e r o u s in mos t of o u r g r eenhouse cul tures , a n d h e a d shape a n d s ty le t m o r p h o l o g y of males a p p e a r to be

4, October 1981

useful s u p p l e m e n t a l t a x o n o m i c characters . O u r obse rva t ions of ma le head shape a n d s tylet m o r p h o l o g y of these four species fu r the r emphas i ze the i m p o r t a n c e of m a l e head shapes and s tylet m o r p h o l o g y in the i den t i f i c a t i on of the fou r c o m m o n species of roo t -kno t nema todes . O u r f indings con- f irm some of C h i t w o o d ' s (2) ea r l i e r f indings as i l l u s t r a t ed in his figures I A (M. arenaria), 5A,K (M. incognita), 2E (M. javanica), and 3C,V,X,Z (M. hapla).

L I T E R A T U R E C I T E D

1. Allen, M. W. 1952. Observations on the genus Meloidogyne Goeldi, 1887. Proc. Helrninthol. Soc. Wash. 19:44-51.

2. Chitwood, B. G. 1949. Root-knot nematodes I. A revision of the genus Meloidogyne Goeldi, 1887. Proc. Helminthol. Soc. Wash. 16:90-104.

3. Dahnasso, A., and J. B. Berg& 1978. Molecular polymorphism and phylogenetic relationship in some Meloidogyne spp.: Application to the taxonomy of Mcloidogyne. J. Nematol. 10:323-332.

4. Dickson, D. W., D. Huisingh, and J. N. Sasser. 1971. Dehydrogenases, acid and alkaline phos- phatases, and esterases for chemotaxonomy of selected Meloidogyne, Ditylenchus, Heterodera and Aphelenchus spp. J. Nematol. 3:1-16.

5. Dropkin, V. H. 1953. Studies on the variability of anal plate patterns in pure lines of Mel- oidogyne spp., the root-knot nematode. Proc. Helminthol. Soc. Wash. 20:32-39.

6. Eisenback, J. D., and H. Hirschmann. 1979. Morphological comparison of second-stage juveniles of six populations of Meloidogyne hapla by SEM. J. Nematol. 11:5-16.

7. Eisenback, J. D., and H. Hirschmann. 1980. Morphological comparison of Meloidogyne males by scanning electron microscopy. J. Nematol. 12: 23-32.

8. Eisenback, J. D., H. Hirschmann, and A. C. Triantaphyllou. 1980. Morphological comparison by LM and SEM of Meloidogyne female head struc- tures, perineal patterns, and stylets. J. NematoL 12: 300-313.

9. Esser, R. P., V. G. Perry, and A. L. Taylor. 1976. A diagnostic compendium of the genus Meloidogyne (Nematoda: Heteroderidae) Proc. Helminthol. Soc. Wash. 43:138-150.

10. Franklin, M. T. 1972. The present position in the systematics of Meloidogyne. OEPP/EPPO Bull. 6:5-15.

11. Hussey, R. S. 1979. Biochemical systematics of nematodes--A review. Helminthol. Abstr., Ser. B, Plant Nematol. 48(4):141-148.

12. Netscher, C. 1978. Morphological and physi- ological variability of species of Meloidogyne in West Africa and implications for their control. Meded. Landbouw. Wageningen, Nederland. 78: 1-46.

13. Sanders, H., and J. Mulet. 1976. 'E' type perineal patterns in Meloidogyne species. Nema- tologica 22:373-376.


14. Sasser, J. N. 1979. Pathogenicity, host ranges and variability in Meloidogyne species. Pp. 257-268 in F. Lambert i and C. E. Taylor, eds. Root-knot nematodes (Meloidogyne species) systematics, biology aml control. New York: Academic Press.

15. Taylor, A. L., V. H. Dropkin, and G. C. Martin. 1955. Perineal pat terns of root-knot nematodes. Phytopathology 45:26-34.

16. Taylor, A. L., and J. N. Sasser. 1978. Biology, identification and control of root-knot nematodes (Meloidogyne species). A cooperative publicat ion of the Depar tment of Plant Pathology, Nor th Caro- lina State University, and the United States Agency for In ternat ional Development. Nor th Carolina State Graphics.

17. Tr ian taphyl lou , A. C. 1960. Sex determina- tion in Meloidogyne incognita Chitwood, 1949 and intersexuality in M. javanica (Treub, 1885) Chit- wood, 1949. Ann. Inst. Phytopathol . Benaki 3:12-31.

18. Tr iantaphyl lou , A. C. 1966. Polyploidy and reproductive patterns in the xoot-knot nematode Meloidogyne hapla. J. Morphol. 118:403-413.

19. Tr iantaphyl lou , A. C. 1979. Cytogenetics of root-knot nematodes. Pp. 85-114 in F. Lamber t i and C. E. Taylor, eds. Root-knot nematodes (Meloidogyne species) systematics, biology and control. New York: Academic Press.

20. Tr ian taphyl lou , A. C., and J. N. Sasser. 1960. Variation in perineal pat terns and host specificity of Meloidogyne incognita. Phytopathology 50:724- 735.

21. Whitehead, A. G. 1968. Taxonomy of Meloidogyne (Nematodea: Heteroderidae) wi th descriptions of four new species. Trans. Zool. Soc. London 31:263-401.

22. Yik, C., and W. Birchfield. 1978. Scanning electron microscopy of perineal pat terns of three species of Meloidogyne. J. Nematol. 10:118-122.

Redescription and Lectotype Designation of Tylenchorhynchus cylindricus Cobb, 19131

Stephen A. Lewis and A. Morgan Golden 2

Abstract: Tylenchorhynchus cylindricus is redescribed and illustrated from N. A. Cobb's original specimens collected in 1910. In 1955 M. W. Allen established a neotype from specimens collected near Cathedral City, California. Recently Cobb's original sketches, line drawings, and balsam slides were rediscovered and examined. T h e specimens collected by Cobb were compared with the neotype established by Allen and with other collections of nominal T. cylindricus. Differences in morphology of the Cathedral City (Allen) and Los Patos (Cobb) popula t ions were observed. Collections of males and females from Cathedral City, California; Mosida, Utah; and Kings County, California; were similar to each other except for some variation in female tail shape. Females in Cobb's collection and in a collection from a beach near Ensenada, Mexico, were similar to each other bu t differed morphologically from other collections. We consider all collections to represent a range of variation within the species. A lectotype and an allolectotype were selected to establish the taxonomic base for the genus. A ru l ing has been requested f rom the In ternat ional Commission of Zoological Nomenclature on the disposition of the neotype. Key words: taxonomy, morphology, grass.

In 1913 Dr. Nathan A. Cobb erected the genus Tylenchorhynchus when he described T. cylindricus found in soil from reclaimed coastal swamp lands in southern California

Received for publication 3 March 1981. 1Contribution No. 1882 of the South Carolina Agricul-

tural Experiment Station, Clemson University. -"Associate Professor of Plant Pathology and Physiology,

Clemson University, Clemson, SC 29631; and Nematologist, Nematology Laboratory, Plant Protection Institute, USDA SEA AR, Beltsville, MD 20705. This study was performed while the senior author was on sabbatical leave in tile laboratory of Dr. Golden. Appreciation is extended for the fi- nancial support of the USDA and for the technical assistance of Donna M. S. Ellington, Support Scientist and Paula Crowley, Laboratory Technician. James G. Baldwin, Depart- ment of Nematology, University of California, Riverside, CA 92521; E. Mae Noffsinger, Division of Nematology, Uni- • ~ersity of California, Davis, CA 95616; and Adam C. Weiner, California Department of Food and Agriculture, Sacra- mento, CA 95814, provided reference specimens for this study.

(3). Since this material was evidently thought by Allen to have been lost, he established a neotype from a popula t ion found in soil near the base of Prunus sp. in Cathedral City, California (1). Specimens of T. cylindricus from Arvin, Victorville, Yuma Mesa, Modesto, and Stockton, Cali- fornia; and from Mosida and Duchesne, Utah; also were studied by Alien. Cobb's measurements, sketches, and ink drawings of T. cylindricus were on file, but the original specimens recently were found at the U. S. Depar tment of Agriculture, Beltsville, Maryland. Examinat ion of this material and the Cathedral City specimens of Allen revealed differences in both males and females.

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