Relationships of Plant Parasitic to Sites in Native Iowa Prairies ~

D. P. SCHMITT and D. C. NORTON 2

Abstract: Soil samples were collected from three native Iowa prairies and analyzed for plant paiasitic nematodes and selected soil properties. Sites or nematodes were clustered with similarities related to habitat by a cluster analysis of site by species and of nematodes by site. Some nematodes occurred in a wide range of prairie habitats, whereas others were more restricted. For example, greater numbers of Xiphinema americanum were in the low, well-drained sites than in the low wet sites or upland dry sites. Wet sites contained fewer nematodes than well-drained sites. Well-drained sites contained mainly maximus, Helicotylenchus pseudorobustus, and X. americanum. Wetter sites contained almost exclusively X. chambersi, H. hydrophilus, Telylenchus ]octus, and an undescribed species of Tylenchorhynchus. Key words: habitat relationships, H. leiocephalus, Aorolaimus torpidus, T. nudus.

Investigations of plant parasitic nematodes Moraine. Hayden Prairie in Howard County is in native grasslands in the United States have about 135 miles northeast of the Kalsow Prairie resulted mostly in faunistic lists and associated and about 200 miles east of the Cayler Prairie, plants (4, 5, 6, 11). That more nematode and is in the Cresco-Lourdes-Clyde soil studies in native areas have not been made is association. These prairies have never been surprising, since most nematodes in USA cultivated, and they have been set aside as cultivated soils probably had their ancestry in preserves, two of them being registered Natural virgin areas in relatively recent times. Studies in Landmarks. The Kalsow, Cayler, and Hayden natural areas perhaps would give insight to the prairies consist of 64.74, 42.08, and 97.10 presence and ecology of plant parasitic hectares (160, 104, and 240 acres), nematodes in agricultural soils, and to their respectively. Although these prairies have never possible importance in the native ecosystem. been cultivated, they are now mowed or burned The purposes of this study were to catalog periodically to maintain their natural state. stylet-bearing nematodes and to analyze their Sites varied from moraine summits to potholes prairie relationships by cluster analysis. (undrained depression), with concomitant Emphasis was placed on the , and on changes in vegetation. Xiphinema and Trichodorus in the Samples of 600-700 cc of soil were taken 4 Dorylaimida, since these taxa are associated times at 2-month intervals from February frequently with cultivated plants and contain through September 1968 from the 0-15 cm (0-6 economically important species. inch) depth with a 7.6 cm (3-inch) diam soil bucket auger. Nematodes were extracted from MATERIALS AND METHODS the soil within 1 day of sampling by a SITES AND SAMPLE PROCESSING: The modification of the Christie and Perry three state-owned prairies used in this study extraction method (1). Briefly, this consisted of have a rolling topography, and are remnants of wet-sieving 250 cc soil through 35-, 60-, 100-, the once vast tall-grass prairie. Cayler Prairie in and 200-mesh sieves. The residue on the 100- Dickinson County and Kalsow Prairie in and 200-mesh sieves was placed on a Baermann Pocahontas County, 75 miles to the southeast, funnel for 44 hr. Then 10 ml of water were are composed of several soil series in the tapped from each funnel and the nematodes Clarion-Nicollet-Webster soil association. The counted. Roots were collected from the Cayler Prairie is contained within the Altamont 35-mesh sieve and processed for endoparasitic nematodes by thin-water-t'tim extraction in a petri dish. The residue on the 60-mesh sieve was Received for publication 10 January 1972. examined for cyst nematodes. Total nematode 1journal Paper No. J-7139 of the Iowa Agriculture numbers were estimated by counting 10% of and Home Economics Experiment Station, Ames, Iowa. Project No. 1337. the nematodes in a sample. Numbers of each 2Department of Botany and Plant Pathology, Iowa species were estimated by identifying 20 State University, Ames, Iowa 50010. Present address specimens of a genus, or all specimens, if fewer of senior author: Division of Plant Industries, Tennessee Department of Agriculture, Box 40627, than 20 individuals were available. Since the Melrose Station, Nashville, Tenn. 37204. We express extraction procedures used are inefficient in our gratitude to Roger Mrachek for assistance with the statisticalanalysis. isolating Criconemoides and Longidorus 200 Plant Parasitic Nematodes: Schmitt, Norton 201 species, little importance was given to data on prairies, respectively, (Table 1) were made using these genera. Each soil sample was analyzed for similarity coefficients to determine a texture (12), pH (7), and organic matter classification scheme of nematode associations content (7). Since nearly all samples consisted (9, 10). Only maximum numbers obtained for a of mixed root systems, a vegetation analysis given nematode at each site were used in the was made at each site (Table 1). cluster analyses, since data from other times of SIMILARITY COEFFICENTS: Cluster the year usually merely reflected periodicity of analyses employing samples from 12, 23, and population size. Periodicity aspects will be 15 sites from the Cayler, Hayden, and Kalsow reported elsewhere.

TABLE I. Dominant vegetation, nematodes, and soil pH, texture, and percentage organic matter in the Cayler, Hayden, and Kalsow prairies, Iowa, 1968.

Site Percentage clusters Dominant stylet-b Percentage organic in Fig. 2 Dominant vegetationa bearing nematodes sand-silt-clay pH matter

A Solidago canadensis L. Xiphinema americanum 23-40-37 5.6 7.8 L. to to to 39-49-12 6.2 10.6 B Andropogon gerardi Vitman Helicotylenchus 27-39-34 5.7 data Poa pratensis pseudorobustus to to Solidago canadensis Tylenchorhynchus 42-55-3 6.9 lost nudus C Poa pratensis Xiphinema americanurn 22-38-40 5.6 8.7 to to to 34-48-17 6.8 11.5 D Poa pratensis Aorolaimus sp.b 27-43-30 5.4 7.2 Salix humilis Marsh. Helicotylenchus sp. to to to Aphelenchus sp. 36-39-25 5.8 7.6 Xiphinema americanurn E Achillea lanulosa Nutt. b Tylenchorhynchus 28-39-33 5.6 8.5 Cirsium arvense (L.) Scop. nudus to to to Poa pratensis Aphelenchus sp. 36-39-25 7.6 9.2 Setaria viridis (L.) Beauv. Solidago canaden~is F Achillea lanulosa u Helicotylenchus 12-21-67 5.5 5.7 A ndropogon gerardi dihystera to to to Lathyrus venosus Muhl. Helicotylenchus 27-48-24 5.9 9.8 Poa pratensis pseudorobustus Spartina pectinata Link Sporobolus heterole~is Gray G Andropogon gerardi ° Helicotylenchus 27-44-28 5.2 6.3 Poa pratensis digonicus Perry to to to Salix humilis Xiphinema americanum 27-40-33 5.5 6.9 Sporobol~s heterolepsis H Carex sp.u Helicotylenchusb 29-38-33 5.1 8.0 Baptisia leucophaea Nutt. dihystera to to to Fragaria virginiat~a Duchesne Helicotylenchus 39-44-17 6.2 11.8 Poa pratensis pseudorobustus Spartina pectinata Heterodera sp. Aphelenchus sp. Aphelenchoides sp. Carex sp. b Tylenchorhynchus sp.b 20-37-43 5.0 5.4 Poa pratensis Tylenchorhynchus to to to Polygonum coccineum Muhl. nudus 39-41-20 7.5 12.5 Salix interior Rowlee Tetylenchus ]octus Scirpus fluviatilis (Torr.) Gray Helicotylenchus hydrophilus Xiphinema americanum Xiphinema chambersi aSpecies listed were dominant in most of the sites in a given cluster. bNo common dominant species but includes species listed. 202 Journal of Nematology, Vol. 4, No. 3, July 1972

The cluster analysis measures only positive hydrophilus Sher, galeatus (Cobb) associations in the range 0 < S < 1 by the Thorne, and Xiphinema chambersi Thorne were equation: closely associated (Fig. 1A). Another hierarchy was established by nematodes recovered from the well-drained sites (Fig. 1B). Here, X. n 2W k arnericanum Cobb-Mononchidae, E S jr.au =k=laik+bjk Aphelenchus-Aphelenchoides groups clustered with Helicotylenchus dihystera (Cobb) Sher and H. pseudorobustus (Steiner) Golden because they occurred together frequently. where S = similarity between sites or species i Most clusters in Fig. 1C probably indicate and sites or species j; n = number of sites or that these species prefer different ecological species; aik = value of either site or species i, or niches, since the species of a cluster occurred species or site k; bjk = value of either site or together only once and independently several species j, or species or site k; and Wk = value in times, often in low numbers. A possible common between site or species i and species or exception is the clustering of H. exaUus and G. site j for species or site k. aciculus, which occurred together in large numbers once in an isolated habitat containing upland vegetation, such as Poa pratensis and RESULTS Solidago canadensis; the site was located at the The classification of nematode species by bottom of a slope near an intersection of two site clustering based on presence-absence and drainage systems. population size is presented in Fig. 1. Basically, The clustering of nematode species by sites three groups of nematodes were formed: (i) as in Fig. 1A-C brings together certain pothole-area-inhabiting species (Fig. 1A); (ii) associations of nematodes, but provides only species that occurred together frequently in general information of nematode clustering by well-drained areas (Fig. 1B); and (iii) nematodes habitat. The habitat relationships are further that occurred infrequently but clustered elucidated by clustering sites by nematode together once with another species (Fig. 1C). In species (Fig. 2A-I). Some sites were combined Fig. 1A-C, the closer the connecting lines for statistical purposes. Ecological data are between two nematode taxa and the higher the summarized in Table 1. Five clusters of habitats similarity coefficient (0.0-0.7), the more closely considered meaningful (Fig. 2A-I) were: (i) the associated were the taxa by presence-absence drier low areas of the Kalsow and Hayden and abundance. A high similarity coefficient prairies where relatively large numbers of X. (maximum 1.0) indicates that (i) the nematodes americanum, other dorytaims, and non-stylet either were found together consistently as with nematodes, and the consistent small population the dorylaims and non-styler nematodes, size of the Mononchidae were responsible for although in varying numbers; or (ii) they were the clustering (Fig. 2A); (ii) the summit and present in large numbers at one site but few high shoulder sites of the Kalsow and Cayler occurred independently elsewhere, as with prairies, characterized by Tylenchorhynchus Helicotylenchus exallus Sher and Gracilacus nudus Allen, H. pseudorobustus, moderately aciculus (Brown) Raski; or (iii) they were found high numbers of dorylaims and non-stylet only once in low numbers at the same site but nematodes, and consistent presence but low not at all elsewhere, as with H. labiodiscinus numbers of X. americanum (Fig. 2B); (iii) Sher and Pratylenchus sp. slopes scattered throughout the prairies, Some of the most consistent clustering characterized by low to moderately low occurred in the potholes and their peripheral numbers of stylet and non-stylet nematodes zones in which an undescribed species of (Fig. 2C); (iv) mixed sites that contained small Tylenchorhynchus, Helicotylenchus to medium size populations of many nematodes

FIG. 1. Cluster analysis classification of nematodes by sites in Kalsow Prairie, Pocahontas County, Iowa; Cayler Prairie, Dickinson County, Iowa; and Hayden Prairie, Howard County, Iowa. 1968. Genera listed with and without species indicate different taxa, the latter being mostly unidentifiable by us and possibly new species. A. Pothole area-inhabiting species; B. species that occurred together frequently in well-drained sites; C. nematodes that occurred infrequently but clustered together once with another species. See text for details. Plant Parasitic Nematodes: Schmitt, Norton 203

HIRSCHMANNIELLA PRATYLENCHUS HELICOTYLENCHUS LABIODISCINU~ TETYLENCHUS JOCTUS TYLENCHORHYNCHUS ACUTUS HELICOTYLENCHUS DIGONICUS LONGIDORUS ROTYLENCHUS V-- CRICONEMOIDES CURVATUM GRACILACUS ACICULUS I HELICOTYLENCHUS EXALLUS 1 TYLENCHORHYNCHUS TESSELATUS F--I HETERODERA CRICONEMOIDES }F-- TYLENCHORHYNCHUS SILVATICUS PRATYLENCHUS HOPLOLAIMUS I TYLENCHORHYNCHUS LEPTUS PARATYLENCHUS NANUS AOROLAIMUS PARATYLENCHUS PROJECTUS PARATYLENCHUS BREVIHASTUS XIPHINEMA I i HELICOTYLENCHUS PLATYURUS 1 NON-STYLET NEMATODES- DORYLAIMS 1 TYLENCHORHYNCHUS NUDUS HELICOTYLENCHUS TRICHODORUS HELICOTYLENCHUS PSEUDOROBUSTUS | I APHELENCHOIDES APHELENCHUS ~ I MONONCHIDAE XIPHINEMA AMERICANUM HELICOTYLENCHUS DIHYSTERA AOROLAIMUS TORPIDUS HELICOTYLENCHUS LEIOCEPHALUS TYLENCHORHYNCHUS MAXIMUS HELICOTYLENCHUS HYDROPHILUS ] HOPLOLAIMUS GALEATUS XIPHINEMA CHAMBERSl- TYLENCHORHYNCHUS SP. i P- C:)

0 0 SIMILARITY COEFFICIENT 204 Journal ofNematology, Vol. 4, No. 3, July 1972

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SIMILARITY COEFFICIENT Plant Parasitic Nematodes: Schmitt, Norton 205

(Fig. 2H); and (v) low, poorly drained areas and the likelihood of finding X. americanum containing marsh to semi-aquatic plant species and Mononchidae together are good in the (Fig. 21). The site clustering in Fig. 2I can be prairies, but Tylenchorhynchus rnaxirnus Allen subdivided into potholes which are occurring with H. leiocephalus is less probable. characterized by Tylenchorhynchus sp., The lower the acceptance level, the more Tetylenchus joctus Thorne, 11. hydrophilus, and heterogeneity is involved. Many other types of X. chambersi, and poorly drained non-pothole predictions are conceivable from studies -f this areas which contained few nematodes of any type, such as changes in nematode faro with kind. concurrent changes of habitat by cultivation, The clusters in Fig. 2D-G were formed soil conservation, and other cultural practices. mainly by similar numbers of dorylaims The various ranges of soil texture, pH, (excluding Xiphinema, Trichodorus, and organic matter, and vegetation may be Longidorus) and non-stylet nematodes. There is indicative of certain relationships of nematodes little similarity between the stylet-bearing to the ecosystem. Further experimentation is nematode taxa. This has little meaning with necessary, however, before conclusive cause and regard to the data collected for this study. effect relationships can be accepted with confidence. Soil pH, percentage of sand, and organic matter were reported eadier to be DISCUSSION correlated with certain nematode abundance in Due to the complexity of the biological and the Kalsow Prairie (8). Such correlation aids in physical components of the rhizosphere, it is the interpretation of data, but does not reveal difficult to categorize nematodes into habitats the perspective that cluster analysis does. being governed by a single or few factors. Whereas topographic and vegetational Cluster analysis enables one to look for relationships appear to be the most important groupings which aid in a clearer perspective factors governing nematode populations in this than does a statistic such as correlation study, sufficient information was not obtained coefficients. Ferris, et al. (2) showed that a concerning other factors and the similar analysis was useful in grouping interrelationships involved to state that other nematodes in soybean fields by location in factors are not important. Kimpinski and Welch Illinois and Indiana. The main basis of (3) concluded that the amount of plant clustering was on light- and dark-colored soils. material was the most important factor The type of cluster analysis employed in our influencing nematode populations in Manitoba study uses population levels as well as in which Bromus inermis and Poa compressa presence-absence data. Habitat is probably the constituted 88-95% of the vegetation. most relevant consideration involved in the Differences in nematode numbers were separation of groups. Nematode habitat correlated with nitrogen, potassium and soluble differences were evident in the classification salts, but not with soil texture. scheme (Fig. 1,2; Table 1). The types of clustering of sites by species The hierarchial scheme resulting from and species by sites indicates that the prairies cluster analysis should provide a means of are more heterogeneous within a prairie than predicting the probability of finding certain among prairies, and that one can expect to find nematodes. For example, one would expect to similar species in similar habitats in all prairies find X. americanum in low, well-drained areas, of the type studied.

FIG. 2. Cluster analysis classification of sites by nematode species in the Kalsow Prairie (sites 1-15), Pocahontas County, Iowa; Cayler Prairie (sites 39-50), Dickinson County, Iowa; and Hayden Prairie (sites 16-38), Howard County, Iowa. 1968. A. Drier low sites of the Kalsow and Hayden prairies consisting of relatively large numbers of Xiphinema americanum, other dorylaims, non-stylet nematodes, and consistent small population size of the Monochidae; B. summit and high shoulder position sites of the Kalsow and Cayler prairies, characterized by Tylenchorhynchus nudus, Helicotylenchus pseudorobustus, moderately high numbers of dorylaims and non-stylet nematodes, and consistent presence but low numbers of X. americanum ; C. scattered slopes characterized by low to moderately low numbers of stylet and non-stylet nematodes; D-G. Clusters containing too few nematodes for meaningful interpretations; H. sites on various slope positions that contained small to medium-sized populations of many nematodes; !. low, poorly drained sites containing marsh to semi-aquatic plant species. See text for details. 206 Journal of Nematology, Vol. 4, No. 3, July 1972

LITERATURE CITED Acad. Sci. Trans. 69:317-334. 7.RUSSEL, D. A. 1967. Laboratory manual for soil I.CHRISTIE, J. R., and V. G. PERRY. 1951. fertility students; modifications by L. R. Removing nematodes from soil. Helminthol. Frederick and J. R. Murphy. Iowa State Univ., Soc. Wash. Proc. 18:106-108. Ames. 46 p. 2.FERRIS, V. R., J. M. FERRIS, R. L. BERNARD, 8.SCHMITT, D. P. 1969. Population patterns of and A. H. PROBST. 1971. Community some styler-bearing nematodes in a native Iowa structure of plant parasitic nematodes related prairie. J. NematoL 1:304 (Abstr.). to soil types in Illinois and Indiana soybean 9.SOKAL, R. R., and C. D. MICHENER. 1958. A fields. J. Nematol. 3:399-408. statistical method for evaluating systematic 3.KIMPINSKI, J., and H. E. WELCH. 1971. The relationships. Univ. Kans. Sci. Bull. ecology of nematodes in Manitoba soils. 38: 1409-1438. Nematologica 17:308-318. 10.SOKAL, R. R., and P. H. A. SNEATH. 1963. 4.NORTON, D. C. 1959. Relationship of nematodes Principles of numerical . W. H. to small grains and native grasses in North and Freeman. San Francisco and London. 359 p. Central Texas. Plant Dis. Rep. 43: 227-235. ll.THORNE, G., and R. B. MALEK. 1968. 5.NORTON, D. C., and P. E. PONCHILLIA. 1968. Nematodes of the Northern Great Plains. Part I. Styler-bearing nematodes associated with plants Tylenchida (Nemata: ). So. Dak. in Iowa prairies. Iowa Acad. Sci. Proc. Agr. Exp. Sta. Tech. Bull. 31. 111 p. 75:32-35. 12.TROEH, F. R., and R. G. PALMER. 1966. 6.ORR, C. C., and O. J. DICKERSON. 1966. Introductory soil science laboratory manual. Nematodes in true prairie soils of Kansas. Kans. Iowa State Univ. Press, Ames. 95 p.

Influence of Temperature on Embryogenesis in Meloidogyne javanica

ALAN F. BIRD 1

Abstract: The optimum temperature for embryogenesis in Meloidogyne ]avanica lies between 25 and 30 C. Embryogenesis is slightly more rapid at 30 C (9-10 days), but more eggs complete development at 25 C (11-13 days). At temperatures of 25, 27.5, and 30 C, embryogenesis is about twice as rapid as at 20 C (23-25 days), and about four times as rapid as at 15 C (46-48 days). Time-lapse studies showed that the thermal optimum is similar throughout the different stages of embryonic development. Key words: embryo, larva, cin6 time-lapse.

The first report on the influence of what is commonly known as hatching) is 30 C. temperature on egg development in root-knot To determine whether different stages of nematodes was by Tyler (6) in 1933. She found embryogenesis of M. ]avanica have different that embryogenesis of eggs in hanging drop thermal optima, I studied its embryogenesis at cultures was completed in 9 days at 27 C, different temperatures using time-lapse cin6 whereas it took 31 days at 16.5 C. Bird and photomicrography to record every phase of Wallace (3) showed that over a period of 6 development. Detailed descriptions of the days, the thermal optimum for the hatch of morphological changes occurring during eggs ofMeloidogyne javanica (Treub) Chitwood embryogenesis are not given here, as they did was in the region of 30 C. Subsequently, not deviate from descriptions already published Wallace (7) reported that the thermal optimum (2,4, 5). for embryogenesis is about 15 C, whereas that for eclosion (emergence of larva from egg or MATERIALS AND METHODS Egg masses of M. javanica containing a relatively large proportion of eggs in their Received for publication 25 January 1972. earliest stages of development (4-6 weeks from 1C.S.I.R.O., Division of Horticultural Research, GPO time of infection in glass house) were dissected Box 350, Adelaide, South Australia 5001. The author from the roots of tomato plants. The egg thanks K. W. Crocke~ and B. W. Dolkens for technical assistance. masses were vibrated in a hypochlorite solution