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Interaction of Scutellonerna cavenessi and Glo~nusmosseae on growth and N, fixation of soybean Gaetano GERMANI*, Bernard OLLIVIER* * and Hoang Gia DIEM* * * Laboratoire de Nélnatologie and * * Laboratoire de Microbiologie, ORSTOM, B.P. 1386, D a k a r , Sénégal. SUMMARY The influences of a parasitic nematode (Scutellonema cavenessi) and a vesicular arbuscular mycorrhiza ( G l o m u s mosseae) alone or in combination on growth and N, fixation of one cultivar of soybean (44 A73) were studied in the greenhouse. In combined inoculationsof soybean with G. wosseae and S. cavenessi, development of mycorrhizae nullified the stunting and the reduction of N, fixation caused by the nematode. Growth andN, fixation of mycorrhizal plants were greater t h a n t h a t of non mycorrhizal plants. RÉSUMÉ Interaction de Scutellonema cavenessi et Glomus mosseae sur la croissance et la fixation de N , du soja Les auteurs exposent les résultats de l’inoculation simple et combinée du nématodeScutellonema cavenessi et de l’endomycorhize Glomus mosseae sur le cultivar de Soja 44 A73. Des mesures ont été effectuées au 46e jour du cycle végétatif : elles portaient sur ( 1 ) le poids et la teneur en N et P de parties aériennes ( 2 ) le nombre et le poids des nodules bactériens (3) la fixation de N, (4) l’infection par les nématodes et parles endomycorhizes. Les valeurs des paramètres étudiées sont significativement diminuées par S . cavenessi et significativement au.gmentées par G. mosseae. Dans le cas d’une inoculation combinée des deux organismes, l’effet négatif des nématodes est inhibé : les valeurs des parametres considérées ne sont pas différentes celles de observées par l’effet bénéfique des mycorhizes sur des plantes inoculées avec des mycorhizes seules. Studies on plant parasitic nematode-endomycorrbizainteractionshave been recently discussed inmany reviews (Menge et al., 1977 ; Schenck & Kellam, 1978 ; Schonbeck, 1979). O’Bannon et al. (1979) andO’Bannon and Nemec (1979)baveshown thatstimulation of Citrus growth by Glomus rnosseae or Glonzus etunicatus was to Some extent reduced in the presence of Tylenchulus semipenetrans or Radoplzolus similis. However, mycorrhizal plants parasitized by nematodesalways grow betterthanplants infectedwithnematodesalone(Atilano et al., 1976 ; Roncadori & Hussey, 1977 ; Hussey & Roncadori, 1978 ; O’Bannon et al., 1979). Other papers (Schenck& Kellam, 1978) have also shown variation in host responset o a nematodemycorrhizal complex. The effect of nematodes on the behaviour of vesicular-arbuscularmycorrhizal(VA)fungi is also variable. It may be defrimental (Schenck & ’ Revue Nématol. 4 (2): 277-280 (1981) Kinloch,1974 ; Schenck,Kinloclr & Dickson, 1975)without effect (Atilano et al., 1976 ; Hussey & Roncadori, 1978) or stimulative (Bagyaraj,Manjunath & Reddy,1979). . Many papers have reported significantly reducednumbers of root-knotnematodes or reducedformation of root-gallsindifferent plants preinoculated with Glomus mosseae, Glomus fasciculatus or Glornus macrocarpus (Silrora St Schonbeck 1975 ; Sikora 1978 ; Silrora,1979 ; Bagyaraj, Manjunath & Reddy, 1979 ; Kellam & Schenck,1980).Inversely, other workers have reported greater populations of root knot larvae in mycorrhizal plants than in non mycorrhizal plants (Rich & Bird, 1974 ; Atilano et al., 1976). Preliminary works haveshown thatunder controlled conditions in the laboratory, Scutellonerna cavenessi Sher, 1963 may severely affect growth and N, fixation of soybean and peanut 277 G. Germani, B . Ollivier & H . G . D i e m (Germani, Diem & Dommergues,1980 ; Germani, 1981). It has been recently shown t h a t N, fixation of two cultivars of peanuts was reduced to different degrees b yt h e presence of S . cavenessi in fields studies(Germani,198lb). Thepresentstudyhasbeendesignedto determine the effect of the dual inoculation with. Glomus mosseae and Scutellonema cavenessi on growth and nitrogen fixation of one cultivar of soybean. Material and methods - - Five-day-old seedlings of soybean cv. 44 A 73 germinatedin Sand were transplantedsingly into 20 cm Clay pot containing autoclaved soil. The soilwas a sandy soil from the ORSTOM CenterinDakar(clay3.3% ; silt 4.4%, sand 92.1”,(o; p H : 7.1 ; available P (Olsen) : 104 ppm). The S . cavenessi inoculumwasprepared by extractionfromnaturallyinfested soil under field conditions. The nematodes were extracted bythe Dalmasso’s(1966) simplified technique and observations were made to ensure that t.he inoculumwasfreefromotherpathogens.The extractecl nematodes were then washed several timesinsterilized deionized water. At the timeof transplantion, 5 O00 nematodes wereadded tothe soil. Plantsdesignatedto becomemycorrhizal were inoculatedwith a small pad of spores, hyphae and infected root segmentsobtainedfrom a Vignaun.guiculata infectedwith Glomusmosseae. Soybeanplants of al1 treatments, including controls, were inoculated wit<h a liquid culture of R h i z o b i u m , strain USDA 138. Plants designated t o become non mycorrhizal were similarly inoculat,ed wit,h mycorrhized inoculum washings passed through a 50 pm sieve and a Whatnlan N o 1 filter paper t o standardize microflora. Treat,mentsconsisted of inoculationswith Glomzzsmosseae or S. cauenessi alone,inoculat.ions withboth,andcontrolsinoculatedwith ‘Rhizobium only. Treatments were replicated seven times and arrangedin a completelyrandomizeddesign. Pots were watered daily and stored under greenhouse conditions. 46 days after inoculation plants were harvested. Roots were cleared and stained -.according of Phillips and -- -to - the - - method - ._ 2,78 Hayman (1970) the percentage of root segments infected was then determined on more than100, 3.5 mm length root segments under a dissecting microscope ( x 65). Nematodes populationsin the soil and in the root were estimateda t t h eend of the experiment. Nematodes were extractedfrom fresh soil samplesbyelutriation(Seinhorst,1962) and from roots by mist chambers (Seinhorst, 1950), Nematodes were expressed as numbers per pot. The effect fo nematode-mycorrhizaonplant growth was expressed bythedry weight of shootsmeasured at, harvest after 48 h a t 800. P contents and N contents of dried material of shoots were measured respectively by the . vanadate-molybdate method (Jackson, 1964) and the Kjeldhal met.hod. N, fixation was estimated by the dry weight of nodules measured after 48 h a t 800 and by the acetylene reduction method (ARA) on nodulated roots held in hermetically closed serumbottles. Al1 results wereanalyzedstatisticallyusingtheMannWhitneytest(Snedecor & Cochran,1967). Results and discussion , Data in Table 1 show t h a t S . cauenessi signifcantly affected growth and nitrogen fixation of the host plant as compared t o uninoculated plants. As expected, mycorrhizae plant,s grew better (Fig. 1) and fixed more N, than non mycorrhizal plant (Tab. 1). In the dual inoculation treatment (nematode infected mycorrhizal plants), shoot .and nodules dry weight,, Nand 4’ contentandARAper plant were statistically similar t o t.hat found in plants inoculated with G . mosseae alone. Atilano et al. (1 976),O’BannonandNemec(1979), Kellam and Schenck (1980) have already indicated that the presence of VA mycorrhizal fungi reduce the deleterious activity of nematodes, however, in ‘their experiment the beneficial effect of VA mycorrhiza did not completely compensate forthe damage caused bynematodes.. This experiment suggests t h a t growth of nematode infected mycorrhizal plants is governed b y a balancebetweeninhibitoryfactors (nematode)andstimulatoryfactors (VAmycorrhizae).Thestate of thebalancedepends on the host plant, the nematodes and VA mycorrhizae andsoilenvironment. _ -fungusinvolved, -~ _ . - - - , ~ Revue Nématol. 4 ( 2 ) : 277-280 (1981) : ._ Scutellonema cavenessi, Glornus rnosseae and N , firation of soybean Table 1 Effect of single and combined inoculations witll Scufellonenm cavenessi and Glomus rnosseae o n growth and N, fixation of soybean cv. 44 A73 dry m f . (9) N o ne S . cavenessi G. mosseae S . cavenessi $. G . mosseae 2.7 a 1 b 4.3 c 3.6 c N P ( w l p(l m a ng tl )p l a n f ) 57 a 17 b nunlber dry mt. (UV) 125 c ‘2.0 a 0.8 b 5.8 c 84.5 a 35.3 b 98.0 a 100 c 5.1 c 70.5 c313a hlycorrhizal Nematodes infection nn~oleslplant root segments nurnber infested ( yo) perplant A Rd Nodules SllOOtS 109 a 29.3 b 320 c 3.9 a 0.6 b G a 49.6 a 7.4 a 33.6 b 8 700 a 15 DO0 a Values followed by the same letters are rlot significantly different [ P : .06). Fig. 1. Effect of single or double inoculation wit,h S. cavenessi and G . mosseae on growth of soybean : S. cadenessi ( N ) ; control non inoculated ( C ) ; S. cauenessi and G . rnosseae ( N M ) ; G. mosseae (M.). Thepresentwork shows thattheharmful effect of plantparasiticnematodemay be suppressed by the presence of VA mycorrhizae assuggested bystatisticalanalysis(Tab. 1) : nematode infected mycorrhizal plants grow as well as plant infected with G. mosseae alone. The improved grow:h of plants inoculated with both S . caverressi and G. mosseae %vas probably due to the well-known beneficial effect of mycorrhizae alone without any apparent interactionwithnematodes.Similarobservations have been madebyRoncadoriandHussey (1977), Hussey and Roncadori (1978) and O’Bannon et al. (1979). There is no effect of VA mycorrhizaonthepopulation of S . cavenessi but lower mycorrhizalinfection \vas observed Revue NC1rdol. 4 (2): 277-280 (1981) in mycorrhizal plant inoculated with nematodes ascomparedtohealthymycorrhizalplants. Conclusion In theexpriment carried o u t inoculation with nematodes alone exerted a negative effect ongrowthand N, fixation of soybean ; this effec.t was inhibited b y mycorrhizalinfection to such an estent {bat there was no significant difference between plants jointly inoculated withnematodesand G. mosseae and,plants inoculated with G. mosseae alone. This work inaddition to tbat of many others on the effect of nematode-VAmycorrhizainteractions on 279 G. Germani, B. Ollivier h H . G . D i e m PI-IILLIPS, J.hI. & HAYMAN, D.S. (1970).Improved procedures for clearing roots and staining vesicular arbuscular mycorrhizal fungi for rapid assessment of infection. T r a n s . br. mycol. Soc.,,55 : 155-161. RICH, J.R.6r BIRD,G.W. (1974). Association of earlyseason VA mycorrhizae and increased growth and development of cotton. Phytopathology, 64 : 14211425. REFERENCES RONCADORI,R.W.B HUSSEY,R.S. (1977).Interaction of the endomyc.orrhiza1 fungus Giqaspora marATILANO, R., RICI-I, J.R.,FERRIS, W. L ! hIENGE, J.A. cot.t.on. Phytogarita androot-knotnematodeon (1976). Effect o f Meloidogyne arenaria on endomypathology, 67 : 1507-1511. corrhizalgrape ( V i t i sv i n i f e r a ) rootings(Abst.r.) SCHENCK, N.C., & KELLAM,M.K. (1975). The influence J . Nematol., 5 : 275. of vesicular arbuscular mycorrhizae on disease BAGYARAJ, D.J.,MANJUNATII, A. 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(1979).Predispositionto Citrus limon seedlings to a symbiont, Glomus etuniinfectionbytheendotrophicmycorrhizalfungus cntus and a pathogen Radopholus similis.J . Nematol., Glomusmosseae. In : Lambert.i, F. B Taylor, C.E. I I : 270-275. (Eds). Root-knot Nematodes (Meloidogyne species) ; Systematics, Biology and Confrol. London, Academic O'BANNON, J.H., INSERRA, R.N., NEMEC, S. & Press : 399-404. VOVLAS, N. (1979). The influenceof Glomus mosseae on Tylenchulus semipenefransinfected and uninfected SNEDECOR, G.W. & COCHRAN,W.G. (1967). Sfatisfical Cit,rus limon seedlings. J . Nematol., 11 : 247-250. methods. Iowa State. Univ. Press, sixth Ed., 593 p. plant, growth clearly indicate t.hat these interactions appear complex and seem t o Vary witheachplantspecies-nematode-mycorrhizal fungus species combination as discussed by Schencls. and Kellam (1978). Accepté pour publicafion le 1 8 m a i 1981. 280 Revue Nématol. 4 (2): 277-280 (1981)