Nematodes

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Hoveland et al., 1975. Lesion nematodes. Pratylenchus scribneri (Steiner). West at at., 1988. Kimmons et at., 1990. P penetrans (Cobb) Chitwood & Oteifa.
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MI-1 Nematodes

Patricia Timper USDA-ARS, Tifton, Georgia

Abstract Nematodes may play a major role in limiting persistence and production of tall fescue [Loliuni arundinaceum (Schreb.) Darbysh.I in the southeastern United States. These parasites tend to cause greater plant damage in sandy soils than in soils of heavier texture because light-textured soils are conducive to nematode activity and to drought stress. The lance nematode (Hoplolaimus spp.), the stubby-root nematode [Paratriclwdorus minor (Colbran)], the pin nematode (Paratijlenchus spp.), and the lesion nematode [Pratylenchus scribiwri (Steiner)] all have been shown to damage tall fescue in either greenhouse pots or field plots. The symbiotic endophyte of tall fescue, Neotyphodium coenophialum (Morgan-Jones and Cams) Glenn, Bacon, and Hanlin, confers resistance to some but not to all plant-parasitic nematodes. The mechanism by which the endophyte confers resistance to nematodes in tall fescue is not known. The endophyte is not present in the roots; therefore, the fungus either induces physiological changes in the plant or produces toxins and repellents that are translocated to the roots. lant-parasitic nematodes are pests of most forage and turf grasses (Bernard P et al., 1998; Cook and Yeates, 1993). Damage caused by these nematodes has been documented with pot experiments or field trials comparing experimental units treated with nematicide plots t6 untreated units. Nematode damage is not recognized widely by producers because the signs can be difficult to distinguish from other plant stresses, such as nutrient deficiencies, drought, heavy grazing, and other root diseases. Worldwide, the major nematode parasites of Lolium spp. are cyst nematodes (Heterodera spp.), root-knot nematodes (Meloidogyne spp.), seed gall nematodes (Anguina spp.), lesion nematodes (Pralenchus spp.), and spiral nematodes (He1icoti1enchus spp.).

Nematodes Associated with Tall Fescue There are few reports of nematodes damaging tall fescue except in sandy soils of the southeastern United States. In that region, nematodes may play a major role in limiting persistence and production of tall fescue (Hoveland et al., 1975). Several genera of plant-parasitic nematodes have been found in association with tall fescue (Table 10-1).

Copyright © 2009. American Society of Agronomy, Crop Science Society of America. Soil Science Society of America, 677 S Segoe Road, Madison, WI 53711, USA. Tall Fescue for the Twenty-first Century. H.A. Fribourg, D.B. Hannaway, and C.P. West (ed.) Agronomy Monograph 53. 151

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Table 10-1. Frequency of tall fescue fields infested with various plant-parasitic nematodes. Nematode

Genus

North Carolinat

Alabamat % 53 18 78 51 13 - 9 11 7 6

Arkansas 11111TStubby-root nematode Paratrichodorus 50 12 Stunt nematode Tylenchorhynchus 45 27 Spiral nematode Heilcotylenchus 45 0 Dagger nematode Xiphinema 45 0 Lance nematode Hoplolaimus 25 2 Ring nematode Mesocriconema 5 2 Pin nematode Paratylenchus 5 5 Lesion nematode Pratylenchus 0 11 Root-knot nematode Meloidogyne - 2 Cyst nematode Heterodera - 0 t Soil samples from 40 field sites were collected in 1959 and 1960 (McGlohon et al., 1961). Soil samples from 87 and 86 field sites were collected in 1982 and 1983, respectively. Percentages are the means of the 2 yr (Pedersen and Rodriguez-Kabana, 1984). § Percentages are the means of 32 samples collected in Fayetteville and 34 samples collected in Hope AR in 2006 (Olivera and West, personal communication, 2007)

Damage by Nematodes Root feeding by ectoparasites, such as the spiral (He1icotilt'nc/ui spp.), stubby(Paratrichodorus spp.), and stunt nematodes (Ti1enchorhtnchus spp.), causes root stunting and pruning that can restrict root penetration in soil (Fig. 10-1). Endoparasites, such as lesion (Pratylenchus spp.) and root-knot (Meloidogyne spp.) nematodes result in necrotic lesions and galling that impair root function (Fig. 10-2 and 10-3). Nematodes tend to cause greater plant damage in sandy soils because these soils are conducive to nematode activity and to drought stress. root Hoveland et al. (1975) observed that the roots of two tall fescue cultivars were shallower in a sandy soil infested with the lance (Hoplolaimus spp.), stunt, and stubby-root nematodes than in the same soil treated with a nematicide (carbofuran, 2,3-dihydro-2,2-dimethyl-7-benzofuranylmethylcarbamate) or a broad-spectrum fumigant (methyl bromide). They speculated that root pruning by the nematodes led to greater stand loss during periods of drought. Moreover, forage yields in the second year of production were reduced by 28 and 52% in untreated plots compared to plots treated with the nematicide and fumigant, respectively. In greenhouse pots, single species infestations of lance, stubby-root, or pin nematode (Paratylenchus spp.) reduced top weight of 'Kentucky 31' (KY-31) tall fescue over that of noninfested controls (McGlohon et al., 1961). The lance and stubby-root nematodes also reduced root weight. In another greenhouse experiment, forage yields of 'Kentucky 45-50' tall fescue were reduced by the lesion nematode (P. scribneri) when compared with noninoculated controls (Minton, 1965).

Effect of Fungal Endophyte The symbiotic endophyte of tall fescue, N. coenophialuni, confers resistance to some but not to all plant-parasitic nematodes (Table 10-2). Determinations of such effects were made by comparing nematode numbers in endophyte infected tall fescue (E+) and in tall fescue without the endophyte (E-). The effect of the endophyte is often dramatic, with nematode numbers in E+ plants being less than 10% of those in E- plants for root-knot (Meloidogyne mar ylandi) and lesion (P. scribneri) nematodes (Elmi et al., 2000; Kimmons et al., 1990; West et al., 1988).



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Ok Fig. 10-1. Left: The lance nematode (Hoplolaimus spp.) may feed on the outside of the root, embedding only its head, or it may completely enter the root to feed (photo: R.F. Davis). Right: Roots damaged by lance, sting, and stubby-root nematodes are restricted in their growth and may have necrotic lesions (photo: N.A. Minton).

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Fig. 10-2. Left: The lesion nematode (Pratylenchus spp.) spends most of its life within the root where it feeds on cells in the cortex (photo: U. Zunke). Right: Feeding and migration of lesion nematodes within the roots result in necrotic lesions and reduced root efficiency (photo: A. France).

Fig. 10-3. Left: Roots galled by root-knot nematodes (Meloidogyne spp.) (photo: G. Caubel). Right: Stained root-knot nematode showing swollen female feeding in vascular system and egg mass protruding from the gall (arrow) (photo: W.F. Mai).

NOR

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Table 10-2. Nematode parasites of tall fescue.



Nematode Cyst nematode Heterodera zeae (Koshy, Swarup, and Sethi) Lance nematode Hoplo!aimus galeatus (Cobb) Lesion nematodes Pratylenchus scribneri (Steiner)

Resistance conferred by endophytet

Ringer et al., 1987 Hoveland et al., 1975 West at at., 1988 Kimmons et at., 1990 Thies at at., 1995



P penetrans (Cobb) Chitwood & Oteifa Pin nematode Paratylenchus spp. Paratylenchus projectus (Jenkins) Root-knot nematodes Meloidogyne mary!andi ( Jepson and Golden) M. naasi (Franklin) Spiral nematodes Hellcotylenchus dihystera (Cobb) Sherr H. pseudorobustus (Steiner) Sting nematode Belonolaimus longicaudatus ( Rau) Stubby-root nematodes Paratrichodorus minor (Colbran) Stunt nematodes Tylenchorhynchus acutus (Allen) T claytoni (Steiner) T maximus (Allen)

Reference

Oday at at., 1993 Bernard at at., 1998 Elmi et at., 2000; Kimmons at at., 1990 Person-Dedryver and Fischer, 1987 R NR

Pedersen et at., 1988 Kimmons et at., 1990 Holdeman and Graham, 1953



R NR

Pedersen et at., 1988 Timper and Bouton, 2004 West at at., 1988 Krusberg, 1959 Bernard et at.. 1998

t R, numbers of nematodes were found to be lower in tall fescue infected with the wild endophyte (E+) N. coenophialum than in endophyte free fescue (E-). NR, numbers of nematodes were not different in E+ and E- tall fescues. ?, effect of endophyte on nematode numbers is unknown.

The spiral nematode (Hellcat ylenchus pseudorobustus) represents the only welldocumented case of a nematode that is not affected by the endophyte status of tall fescue (Davis et al., 2004; Kimmons et al., 1990). Nematodes that are found frequently in association with tall fescue (Table 10-1), such as the stubby-root and dagger nematodes (Xiphinema spp.), also are probably not affected by the endophyte. Pedersen et al. (1988) reported greater numbers of stubby-root nematode in root samples from E— than from E+ KY-31; however, Timper and Bouton (2004) observed similar numbers of this nematode in pots containing E+ and E— plants of both 'Georgia 5' and 'Jesup' tall fescues. They also showed that Jesup appeared to be resistant to reproduction of the stubby-root nematode, whereas Georgia 5 was susceptible (Fig. 10-4).

Mode of Action of Resistance The mechanism by which the endophyte confers resistance to nematodes in tall fescue is not known. The endophyte is not present in the roots; therefore, the fungus either induces physiological changes in the plant or produces toxins and repellents that are translocated to the roots. Indeed, resistance to insects in E+ tall fescue is due in part to alkaloids produced by the endophyte in the leaf sheath and translocation to the foliage (see Chapter 9, Popay, 2009, this publication). These alkaloids (see Chapter 13, Bush and Fannin, 2009, this publication) deter insect feeding and reduce survival of insects that feed on the foliage of E+

• Nematodes



155 Fig. 10-4. Average number of lesion

Q.

nematodes (Pratylenchus scribneri)

•E+ LIE

per pot. Each pot contained three plants of a single cultivar either infected with the wild endophyte (E+) or endophyte free (E-).

a,

E a) z Jesup Georgia 5 Tall fescue cultivar

plants (Siegel et al., 1990). Because ergot alkaloids are not involved in resistance to P. scribneri in perennial ryegrass (Lolium perenne L.) (Panaccione et al., 2006), they

probably also are not involved in resistance to nematodes in tall fescue.

Effect of Endophyte Strains Recently, strains of N. coenophia/uni have been isolated from wild tall fescues growing in the Mediterranean region and artificially inoculated into elite tall fescue cultivars (see Chapter 19, Hopkins et al., 2009, this publication). These strains were selected because they result in low to nil levels of ergot alkaloids, yet retain many of the beneficial traits conferred to the plant-endophyte association, such as drought tolerance (see Chapter 4, Belesky and West, 2009, this publication) and insect resistance. One of these novel endophytes (AR542) has been released by Grasslands AgResearch in New Zealand under the trademarked name MaxQ (Pennington Seed Co., Madison, GA). Commercially, MaxQ was inserted into either Jesup or Georgia 5 tall fescues. The lesion nematode (Pratylenchus spp.) was associated with poor stand performance of MaxQ at Tifton, GA (Timper, unpublished data, 2000). In a greenhouse experiment, reproduction of P. scribneri in plants infected with either AR542 or another nontoxic strain ('AR584') was not different from that in E- plants (Timper et al., 2005). Because ergot alkaloids are not likely to be involved in nematode resistance in tall fescue, it should be possible to identify nontoxic strains that also confer resistance to nematodes. Identifying the mechanism by which the endophyte suppresses nematode infection and reproduction will aid in the selection of resistant tall fescue-endophyte combinations.

References Bernard, E.C., K.D. Gwinn, and G.D. Griffin. 1998. Forage grasses. In K.R. Barker et al. (ed.) Plant and nematode interactions. ASA, CSSA, and SSSA, Madison, WI. Belesky, D.P., and C.P. West. 2009. Abiotic stresses and endophyte effects. P. 49-64. In H.A. Fribourg, D.B. Hannaway, and C.P. West (ed.) Tall fescue for the twenty-first century. Agron. Monogr. 53. ASA, CSSA, and SSSA, Madison, WI. Bush, L., and F.F. Fannin. 2009. Alkaloids. p.229-250. In H.A. Fribourg, D.B. Hannaway, and C.P. West (ed.) Tall fescue for the twenty-first century. Agron. Monogr. 53. ASA, CSSA, and SSSA, Madison, WI. Cook, R., and G.W. Yeates. 1993. Nematode pests of grassland and forage crops. P. 305-350. In K. Evans et al. (ed.) Plant parasitic nematodes in temperate agriculture. CAB mt., Wallingford, England.

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Davis, L.T., N.L. Bell, R.N. Watson, and T.C. Rohan. 2004. Host range assessment of He/icot ylenchus pseudorobustus (Tylenchida: Hoplolaimidae) on pasture species. J . Nematol. 36:487-492. Elmi, A.A., C.P. West, R.T. Robbins, and T.L. Kirkpatrick. 2000. Endophyte effects on reproduction of a root-knot nematode (Meloidogyne marylandi) and osmotic adjustment in tall fescue. Grass Forage Sci. 55:166-172. Holdeman, Q.L., and T.W. Graham. 1953. The effect of different plant species on the population trends of sting nematode. Plant Dis. Rep. 37:497-500. Hopkins, A.A., M.C. Saha, and Z.-Y. Wang. 2009. Breeding, genetics, and cultivars. p 339-366. In H.A. Fribourg, D.B. Hannaway, and C.P. West (ed.) Tall fescue for the twenty-first century. Agron. Monogr. 53. ASA, CSSA, and SSSA, Madison, WI. Hoveland, CS., R. Rodriguez-Kabana, and C.D. Berry. 1975. Phalaris and tall fescue forage production as affected by nematodes in the field. Agron. J . 67:714-717. Kimmons, C.A., K.D. Gwinn, and E.C. Bernard. 1990. Nematode reproduction on endophyte-irifected and endophyte-free tall fescue. Plant Dis. 74:757-761. Krusberg, L.R. 1959. Investigations on the life cycle, reproduction, feeding habits and host range of Tylenchorynchus claytoni Steiner. Nematologica 4:187-197. McGlohon, J.N., J.N. Sasser, and R.T. Sherwood. 1961. Investigations of plant-parasitic nematodes associated with forage crops in North Carolina. North Carolina Agric. Exp. Stn. Tech. Bull. 148. Minton, N.A. 1965. Reaction of white clover and five other crops to Pratylenchus scribneri. Plant Dis. Rep. 49:856-859. Oday, M.H., T.L. Niblack, and W.C. Bailey. 1993. Phytoparasitic nematode populations in Festuca arundinacen field plots in southwestern Missouri. J . Nematol. 25:900-906. Panaccione, D.C., J.B. Kotcon, C.L. Schardl, R.D. Johnson, and J.B. Morton. 2006. Ergot alkaloids are not essential for endophytic fungus-associated population suppression of the lesion nematode, Pratylenchus scribneri, on perennial ryegrass. Nematology 8:583-590. Pedersen, J.F., and R. Rodriguez-Kabana. 1984. Differences among nematode populations in tall fescue pastures in north, central, and south Alabama. Crop Sci. 24:819-821. Pedersen, J.F., R. Rodriguez-Kabana, and R.A. Shelby. 1988. Ryegrass cultivars and endophyte in tall fescue affect nematodes in grass and succeeding soybean. Agron. J. 80:811-814. Person-Dedryver, F., and J . Fischer. 1987 Grasses as hosts of Meloidgoyne naasi Franklin. I. Variation in host status of species and varieties grown in France. Nematologica 33:61-71. Popay, A.J. 2009. Insect pests. p. 129-150. In H.A. Fribourg, D.B. Hannaway, and C.P. West (ed.) Tall fescue for the twenty-first century. Agron. Monogr. 53. ASA, CSSA, and SSSA, Madison, WI. Ringer, C.E., S. Sardanelli, and L.R. Krusberg. 1987. Investigations of the host range of the corn cyst nematode, Heterodera zeae, from Maryland. Ann. Appl. Nematol. 1:97-106. Siegel, M.R., G.C.M. Latch, L.P. Bush, F.F. Fannin, D.D. Rowan, B.A. Tapper, C.W. Bacon, and M.C. Johnson. 1990. Fungal endophyte-infected grasses: Alkaloid accumulation and aphid response. J . Chem. Ecol. 16:3301-3315. J.A., A.D. Petersen, and D.K. Barnes. 1995. Host suitability of forage grasses and legumes for root-lesion nematode Pratylenchus penetrans. Crop Sci. 35:1647-1651. limper, P., and J . Bouton. 2004. Effect of eridophyte status and tall fescue cultivar on reproduction of lesion and stubby-root nematodes. Paper no. 406. In R. Kallenbach et al. (ed.) Proc. 5th Int. Symp. on Neotyphodium/Grass Interactions. Univ. Arkansas, Favetteville, AR. limper, P., R.N. Gates, and J.H. Bouton. 2005. Response of Pratylenchus spp. In tall fescue infected with different strains of the fungal endophyte Neotyphodiuni coenophinlurn. Nematology 7:105-110. \\'ect CF., Fltekor, D.M. Oostcrhuis, ,ii'id R.T. Robbins. 1988. The effect of Acrc,nouiiun COc?IOon the go th and 00001 tode infestation of tail Ieseue. Pta nt Soil 11 2:3-6-