Romania (Quercus cerris, Q. frainetto, Q. robur) and - EdituraSilvica.ro

Ann. For. Res. 54(1): 57-71, 2011Research articlesTable 2 (continuation)Formofthe apex,diameter(mm)Rhizomorphs<strong>and</strong> emergenthyphaeTexture of therhizomorphs<strong>and</strong> emergenthyphae62Mantle,color,textureDistancebetweenconsecutivebranches(mm)Round0.3-0.4Emerginghyphae,right anglessmoothLength ofmycorrizalsystem(mm)Code Host Location Color BranchingSmooth with sulfuryellow granulations2 0.2Round0.4-0.6Round toclavate0.3Round orrelativelyacute0.2-0.4Brown-blackrhizomorphsreticulated<strong>and</strong> smoothSympodial,pinnate, sinuousapexesSulfur yellowMihai Bravu08.1997<strong>Quercus</strong><strong>cerris</strong> +RussulavirescensM18Monopodial 3 0.1-0.3 velvetynone noneBlack-purplish tojet blackDobreti07.1998M19 <strong>Quercus</strong><strong>cerris</strong>Rough withoutconspicuous hyphae11 0.5-1Sympodial, basalconstrictionWhite,shinning,smoothsmoothRusty-black with apinkish tingeTinca09.1998M20 <strong>Quercus</strong><strong>frainetto</strong>Velvety, shinningwhite, relatively rare0.2-0.3or lessYellow. Orange Coralloid 6Dobreti07. 1998Buteni06.2000Round0.3-0.4none none<strong>Quercus</strong><strong>cerris</strong>,Querus<strong>robur</strong>M21Smooth withgranular areas19-29 1.2-2Monopodial,pinnate, loose,sinuous branchesPale yellowwith rusty spots<strong>and</strong> granulationdissolving in KOH10%Giurgiu,Mihai Bravu08. 1997Roundsomewith rustyspots0.3-0.4Ramiedrhizomorphs,interconnectedhairy surface<strong>Quercus</strong><strong>cerris</strong> +RussulaatropurpureaM22Wooly, abundant,dense1-4 0.4Monopodial,pinnate, looseyellowGiurgiu,Mihai Bravu08. 1997Round0.3-0.6Orangerhizomorphssmooth <strong>and</strong>branched<strong>Quercus</strong><strong>frainetto</strong>+XerocomuschrysenteronM23Smooth, rareemerging hyphae(also laticiferoushyphae)5 0.5-0.8Coralloid orpinnateOrange to brownwith whitelaticiferous hyphaeBrganu08.1997Round0.2-0.3Rareemergenthyphaesmooth<strong>Quercus</strong><strong>cerris</strong>+LactariusquietusM24White-yellowishwith silvery areas,wooly1.5-2.2 0.5Monopodial,pinnate, sinuousapexesBlackish brownwith white tingeBrganu08.1997<strong>Quercus</strong><strong>cerris</strong> +SclerodermacitrinumM25

Fodor et al. Mycorrhizal status of several <strong>Quercus</strong> species in <strong>Romania</strong> ...Table 2 (continuation)Code Host Location Color BranchingM26 <strong>Quercus</strong><strong>frainetto</strong>M27M28<strong>Quercus</strong><strong>cerris</strong>,<strong>Quercus</strong><strong>robur</strong><strong>Quercus</strong><strong>cerris</strong> +Amanitamairei,<strong>Quercus</strong><strong>robur</strong>M29 <strong>Quercus</strong><strong>robur</strong>Radna10.1998Radna10.1998,Oradea2000Dobreti07.1998Buteni06.2000Oradea06.2000Buteni06. 2000,Oradea06.2000Yellow-dull brownWhite-yellowish,near hyalineYellow-orangeWhite-yellowishwith rusty areasRepeatedlymonopodial,pyramidal aspect,bent apexesMonopodial tocoralloid, dense,sometimessolitary, basalconstrictionDichotomous tocoralloidPinnatepyramidalM 30All species +CenococcumgeophilumAll locationsJet black withsclerotiaUnbranched orMonopodialpinnateLength ofmycorrizalsystem(mm)Distancebetweenconsecutivebranches(mm)Mantle,color,texture0.7-1 0.2-0.4 farinaceous0.8-1 0.3-1 Wooly, dense4-8 0.1-1Velvety, rare,shinning white4-6 0.2-0.4Granular <strong>and</strong> spikydue to cystidsyellowish1-2.5Stringy <strong>and</strong> shinydue to emergingblack hyphae, grainyFormofthe apex,diameter(mm)Round0.3-0.4Round0.3-0.4Round,slightlybent0.2-0.3Round,hyaline0.3-0.4Round,in olderparts,blackRhizomorphs<strong>and</strong> emergenthyphaeSmooth,ramiedrhizomorphsFan shapedrhizomorphsRarerhizomorphsemergingat rightanglesBundlesof shortemerginghyphaeBlack, rigidemanatinghyphaeSclerotiapresent: black,spherical,grainy,2 mm,hard <strong>and</strong>brittle,coated withsoil particlesTextureof therhizomorphs<strong>and</strong> emergenthyphaesmoothhairysmoothsmoothsmooth63

Ann. For. Res. 54(1): 57-71, 2011wetter <strong>and</strong> milder during the winter. In South,climate is temperate continental, with pronouncedtemperature extremes <strong>and</strong> prolongeddrought during the summer months. Southernforest st<strong>and</strong>s are located in plains, frequentlyexposed to summer drought (Giurgiu - MihaiBravu, Brneti, Vlsia - Buriau, ExperimentalStation tefneti, Brgan, Vldiceasca,Slveti, Snagov, Comana). Comana <strong>and</strong> MihaiBravu are located an the Neajlov riverdelta. The st<strong>and</strong> age varied between 60 <strong>and</strong> 90years.Stressful conditions affecting the trees fromdifferent investigated locations were assignedto groups: (i) soil pollution from an oil extractionplant (Tinca), (ii) several years of recurringdrought (Brgan), (iii) multiple sourcesof city pollution in the city of Oradea, (iv)chronic foliar disease produced by ErysipheResearch articlesalphitoides (Griffon & Maubl.) U.Braun &S.Takam <strong>and</strong> infestations produced by gall insects-Dryomyiacircinans (Giraud) (Dobreti)<strong>and</strong> Cynips quercus-folii (Linnaeus) (Oradea),(v) defoliations produced mainly by Lymantriadispar (Linnaeus) (Tinca).Root processing protocol. Mycorrhizalsystem is dened as a lateral ramication <strong>and</strong>all its tributary apices from a sustaining suberi-ed root, total length varying between 1 <strong>and</strong> 5cm. During the research mycorrhizal root systemswere studied according to this denition,pieces of 10-20 mm being cut <strong>and</strong> investigatedfor alive <strong>and</strong> declining mycorrhizal apices.Blocks of soil of 5 x 5 x 5 cm were excavatedin the rhizosphere of selected tree hostspecies (<strong>Quercus</strong> spp.), in the area of horizontalcrown projection, three trees of the samespecies per st<strong>and</strong>. The blocks were wrapped1614121086420qcaqcbqcbaqcdqcmbqcoqcsNumber of morphotypesqcslqctqcvqcvlqfaqfdqfgqfmbqfslqftFigure 1 Number of mycorrhizal morphotypes by host (<strong>Quercus</strong> <strong>cerris</strong>, Q. <strong>frainetto</strong>, Q. <strong>robur</strong>) <strong>and</strong> locationNotation: qca - <strong>Quercus</strong> <strong>cerris</strong>, Arad; qcbr - <strong>Quercus</strong> <strong>cerris</strong>, Brgan; qcba - <strong>Quercus</strong> <strong>cerris</strong>, Bneasa; qcd- <strong>Quercus</strong> <strong>cerris</strong>, Dobreti; qcmb - <strong>Quercus</strong> <strong>cerris</strong>, Mihai Bravu, qco - <strong>Quercus</strong> <strong>cerris</strong>, F.D. Oradea, qcsl -64Host species<strong>Quercus</strong> <strong>cerris</strong>, Slveti; qcs - <strong>Quercus</strong> <strong>cerris</strong>, tefneti; qct - <strong>Quercus</strong> <strong>cerris</strong>, Tinca; qcv - <strong>Quercus</strong> <strong>cerris</strong>,Vldiceasca; qcvl - <strong>Quercus</strong> <strong>cerris</strong>, Vlsia; qfa - <strong>Quercus</strong> <strong>frainetto</strong>, Arad (Radna); qfd- <strong>Quercus</strong> <strong>frainetto</strong>,Dobreti; qfg - <strong>Quercus</strong> <strong>frainetto</strong>, F.D. Giurgiu (Comana); qfmb - <strong>Quercus</strong> <strong>frainetto</strong>, Mihai Bravu; qfsl -<strong>Quercus</strong> <strong>frainetto</strong>, Slveti; qft - <strong>Quercus</strong> <strong>frainetto</strong>, Tinca; qrb - <strong>Quercus</strong> <strong>robur</strong>, Buteni; qro - <strong>Quercus</strong> <strong>robur</strong>,city of Oradea; qcb - <strong>Quercus</strong> <strong>cerris</strong>, Buteni.

Fodor et al. Mycorrhizal status of several <strong>Quercus</strong> species in <strong>Romania</strong> ...Table 3 Proportion of mycorrhizal apices in root samples (15 mycorrhizal systems selected at r<strong>and</strong>om) collected during the vegetation season from several <strong>Quercus</strong> species, different locations (1996-2001)Tree species, location <strong>and</strong> date Proportion of mycorrhizal apices (%)Q. <strong>cerris</strong>, tefneti (08.1996) 43.5Q. <strong>cerris</strong>, Mihai Bravu (10.1996) 42.0Q. <strong>cerris</strong>, Brganu (10.1996) 85.0Q. <strong>frainetto</strong>, Comana (10.1996) 86.0Q. <strong>cerris</strong>, Tinca (10.1997) 20.0Q. <strong>frainetto</strong>, Radna (10.1998) 30.0Q. <strong>frainetto</strong>, Tinca (09.1998) 32.4Q. <strong>cerris</strong>, Tinca (09.1998) 31.4Q. <strong>frainetto</strong>, Mihai Bravu (10.1996) 46.0Q. <strong>cerris</strong>, Dobreti (07.1998) 46.3Q. <strong>frainetto</strong>, Dobreti (09.1998) 13.1Q. <strong>cerris</strong>, Dobreti (07.1998) 67.6Q. <strong>cerris</strong>, Oradea (09.1998) 67.6Q. <strong>robur</strong>, Buteni (07.2000) 78.0Q. <strong>robur</strong>, city of Oradea (06. 2001) 33.0in paper <strong>and</strong> brought to the laboratory. Thesamples, corresponding to one tree mergedin one composite sample subjected to furtherprocessing. Roots were carefully washed intap water using sieves, placed in Petri dishesof 9 cm <strong>and</strong> observed under stereomicroscopecleaning meanwhile the adhered soil with nebrushes <strong>and</strong> needles. The descriptions of themorphotypes are based on macroscopic charactersfollowing the adapted protocol afterAgerer (1987-2002). Actual mycorrhizas wereconrmed microscopically by the existence ofthe Hartig net <strong>and</strong> mycorrhizal mantle (Nylundet al., 1982).Quantitative analysis. Comparison ofthe mycorrhizal status (relative frequencies ofactive mycorrhizal apices) in 5 root samplestaken from <strong>Quercus</strong> <strong>cerris</strong> at Dobreti wasperformed by means of One-Way ANOVA. Aprevious test of variance homogeneity (Bartlett)conrmed the lack of signicant differenceswith respect to the variances amongsamples. Also Tukey test of pair-wise multiplecomparisons was performed in order to detectany signicant differences in mycorrhizationfrequency in the 5 samples set collected from<strong>Quercus</strong> <strong>cerris</strong> roots at Dobreti. This locationwas selected to perform the specied statisticalanalyses due to the fact that it corresponds tothe highest diversity of morphotypes found atany location, at a particular moment.The association status of different morphotypeswith Coenococcum geophilum Fr., mostfrequently encountered morphotype, was assessedusing Yule coefcient of association.Yule’s Q coefcient of association is a symmetricmeasure, based on the difference betweenconcordant (meaning both absences a,<strong>and</strong> both presences, d) <strong>and</strong> discordant (meaningabsence-presence data, b <strong>and</strong> presence-absencedata, c) data pairs (Singh, 2004).Q = (ad-bc)/(cd+bc)The coefcient takes values between -1 <strong>and</strong>1: -1 corresponds to a complete exclusion ofthe species, 0 corresponds to r<strong>and</strong>om associations<strong>and</strong> 1 to constant associations. Q statisticdenes null relationship as statistical independence.Hierarchical cluster analysis of tree species<strong>and</strong> locations, with regard to mycorrhizal morphotypes,was performed after the calculationof the Sørensen similarity index. The similar-65

Ann. For. Res. 54(1): 57-71, 201166m30m29m28m27m26m25m24m23m22m21m20m19m18m17m16m15m14m13m12m11m10m9m8m7m6m5m4m3m2m10 10 20Figure 2 Frequencies of mycorrhizal morphotypesin root samples of Quecus <strong>cerris</strong>,<strong>Quercus</strong> <strong>frainetto</strong> <strong>and</strong> <strong>Quercus</strong> <strong>robur</strong>in several locations in Southern <strong>and</strong>North-Western <strong>Romania</strong>Research articlesity-dissimilarity matrix was used for clusteringby means of group average method. Statisticaltests were performed using KyPlot program.ResultsThere were identied 30 morphotypes of ectomycorrhizae,corresponding to <strong>Quercus</strong> <strong>robur</strong>,<strong>Quercus</strong> <strong>cerris</strong> <strong>and</strong> <strong>Quercus</strong> <strong>frainetto</strong> in Southern,Western <strong>and</strong> North-Western locations,presented in Table 1. The original descriptions(with the exception of Cenoccocum geophilumdescribed by Agerer in 1987), are presented inTable 2.The investigation of the maximum numberof morphotypes active a certain moment in therhizosphere of the host is 14 (Fig. 1) which isthe real instantaneous value of morphotyperichness (Q. <strong>cerris</strong> at Dobreti).The described morphotypes include only 6cases of identied mycobionts (Amanita maireiFoley, Scleroderma citrinum Pers., Russulaatropurpurea (Krombh.) Britzelm, Lactariusquietus (Fr.) Fr., Russula virescens (Schaeff.)Fr., Boletus chrysenteron Bull.) based on mycelialcontinuity between mycorrhizal mantle<strong>and</strong> the mycelium at the base of the carpophores.Easily recognizable Cenoccocumgeophilum Fr. is also included in morphotypedescriptions. Mantles of mycorrhizas with speciesof Lactarius as mycobionts (as examinedon cross sections of ne roots) exhibit characteristiclaticifers <strong>and</strong> pigments which are alsofound in the structure of the sporocarps. Thoseof Rusulla spp. exhibit distinctive cystidia <strong>and</strong>sulfovaniline reactive cells (Kernaghan <strong>and</strong>Currah 1997).The analysis of frequency distribution of thevarious morphotypes (Fig. 2) shows that thedominating type is Cenococcum geophilum(M30) that is present in all locations. Nextmost frequent morphotype is M2 described inQ. <strong>robur</strong> <strong>and</strong> Q. <strong>cerris</strong> at Buteni, Oradea <strong>and</strong>Slveti but found in almost all locations lessfrequently than C.geophilum.

Fodor et al. Mycorrhizal status of several <strong>Quercus</strong> species in <strong>Romania</strong> ...Table 4 The Yule coefcient of association of Cenococcum geophilum with several other mycorrhizal morphotypes in <strong>Quercus</strong> <strong>cerris</strong>, DobretiAssociationYule coefcient of associationC. geophilum + M10 -0.8004C. geophilum + M17 -0.1287C. geophilum + M8 0.2564C. geophilum + M3 0.2467C. geophilum + M11 -0.0943C. geophilum associates either r<strong>and</strong>omlywith other morphotypes in the same mycorrhizalsystem (values close to 0), or excludesother morphotypes (value close to -1 in the associationwith M10) according to our results, apattern consistent with its dominating position.It is also the most frequent <strong>and</strong> broad spectrumhost associated mycorrhizal type as other authorsreport (Moser et al. 2005).The comparison of the mycorrhizal status(relative frequencies of active mycorrhizal apices)among 5 samples of roots from <strong>Quercus</strong><strong>cerris</strong> at Dobreti by of one way ANOVA resultedin no signicant differences at p > 0.05.Also Tukey test for pair-wise multiple comparisonsdidn’t reveal any signicant differencesbetween samples.Søresen similarity index (Table 4) calculatedin order to compare locations <strong>and</strong> <strong>Quercus</strong>species (within site <strong>and</strong> between sites) showmaximum values in the following cases: <strong>Quercus</strong><strong>frainetto</strong> at Tinca with <strong>Quercus</strong> <strong>cerris</strong> atOradea (0.72), <strong>Quercus</strong> <strong>robur</strong> at Buteni with<strong>Quercus</strong> <strong>robur</strong> in the city of Oradea (0.61),<strong>Quercus</strong> <strong>cerris</strong> <strong>and</strong> <strong>Quercus</strong> <strong>frainetto</strong> at MihaiBravu (0.57).The analysis of the dendrogram resultedfrom the ordination of Sørensen similarity matrix,comparing different sites <strong>and</strong> tree hostswith regard to identied morphotypes (Fig. 3),reects the association between similar siteswithin same geographical <strong>and</strong> meso-climaticarea. Within same location, different host speciesare highly similar with respect to their mycorrhizalassociates, such as Q. <strong>cerris</strong> <strong>and</strong> Q.<strong>frainetto</strong> at Dobreti or Tinca (South-West atMihai Bravu).A distinct cluster is formed by hosts locatedin forest st<strong>and</strong>s from Southern <strong>Romania</strong> wherethese are vegetating in the plain <strong>and</strong> are exposedto temperate-continental climate withharsh winters <strong>and</strong> dry summers. Another distinctcluster is formed by hosts vegetating inst<strong>and</strong>s from Mihai Bravu, in the Neajlov riverdelta, characterized by wetter soil conditionsas compared to other Southern locations. However,Q. <strong>frainetto</strong> from Comana, a nearby location,to Mihai Bravu clusters together withother Southern locations characterized bydrier soil conditions. North Western locationscluster, together presents same pattern of associationwith their mycobionts, including aslocation Tinca <strong>and</strong> Oradea. <strong>Quercus</strong> <strong>robur</strong> ishighly dissimilar to other host species withregard to associated mycobionts <strong>and</strong> clustersseparately. Recurrent associations, in this caseof ectomycorrhizal mophotypes, correspondto fundamental properties of the interactionbetween species <strong>and</strong> their physical (site) <strong>and</strong>biotic environment (hosts) (Legendre & Legendre,1998).Previous studies (Timofte 2007) reported thepossibility to obtain micropropagated plantletsof Q. <strong>robur</strong> <strong>and</strong> Q. <strong>frainetto</strong> by means of somaticembryogenesis initiated from acorns.The embryos can be converted to plantletswhich, theoretically, can be outplanted.DiscussionThe energy ow through the mycorrhizal networksrepresents a major food chain in the foresttrophic web. The network represented by67

Ann. For. Res. 54(1): 57-71, 2011Research articlesLocations <strong>and</strong> <strong>Quercus</strong> speciesDistanceFigure 3 Cluster Analysis of mycorrhizal morphotypes associated with <strong>Quercus</strong> <strong>cerris</strong>, Q. <strong>frainetto</strong> <strong>and</strong> Q.<strong>robur</strong> using Sørensen Similarity Index <strong>and</strong> Average Linkage Method.Notation: 1 - <strong>Quercus</strong> <strong>robur</strong>, Buteni; 2 - <strong>Quercus</strong> <strong>robur</strong>, Oradea; 3 - <strong>Quercus</strong> <strong>cerris</strong>, Brneti; 4 - <strong>Quercus</strong><strong>frainetto</strong>, Mihai Bravu; 5 - <strong>Quercus</strong> <strong>cerris</strong>, Mihai Bravu; 6 - <strong>Quercus</strong> <strong>frainetto</strong>, Dobreti; 7 - <strong>Quercus</strong> <strong>cerris</strong>,Dobreti; 8 - <strong>Quercus</strong> <strong>cerris</strong>, Tinca; 9 - <strong>Quercus</strong> <strong>frainetto</strong>, Tinca; 10 - <strong>Quercus</strong> <strong>cerris</strong>, Oradea; 11 - <strong>Quercus</strong><strong>cerris</strong>, Arad; 12 - <strong>Quercus</strong> <strong>frainetto</strong>, Arad (Radna); 13 - <strong>Quercus</strong> <strong>cerris</strong>, tefneti; 14 - <strong>Quercus</strong> <strong>cerris</strong>,Vlsia; 15 - <strong>Quercus</strong> <strong>cerris</strong>, Slveti; 16 - <strong>Quercus</strong> <strong>frainetto</strong>, Slveti; 17 - <strong>Quercus</strong> <strong>cerris</strong>, Vldiceasca; 18- <strong>Quercus</strong> <strong>cerris</strong>, Bneasa; 19 - <strong>Quercus</strong> <strong>frainetto</strong>, Comana (Giurgiu); 20 - <strong>Quercus</strong> <strong>cerris</strong>, Brgan.mycelia <strong>and</strong> assimilative roots associated inmycorrhizae operates in allocations <strong>and</strong> reallocationsof nutrients, water, in blocking thepotential root infection courts relying on thediversity of mycobionts, each performing adifferent job. The identied 30 morphotypes,associated with species of <strong>Quercus</strong>, are assigneddifferently, depending on geographicaldistribution of hosts, on health status (there arefewer root active apices in trees vegetating understressful conditions) <strong>and</strong> host species.The niche partitioning among several mycobiontsis possible because the ectomycorrhizalfungi differ in their tolerance to water stress<strong>and</strong> temperature extremes, in their ability totake up different nutrients, their resistance topathogens (Jones et al. 1998). The instantaneousrichness value, for morphotypes active ata certain moment on the same host species isfar less than the total richness of the existingmycobionts, associated with a host, as can berevealed by molecular methods. During the investigationsof the present study, the maximum68number of active morphotypes associated to ahost species, in a particular location, was of 14(<strong>Quercus</strong> <strong>cerris</strong> at Dobreti), a fact that is concordantwith the hypothesis of redundant speciesas functional insurance (Yachi & Loreau,1999). There is a sequential mobilization ofmycorrhizal fungi from the common speciespool, active within a particular time window.The degree of mycorrhization differs amongtrees, parts of the root system, <strong>and</strong> phenologically.Our ndings revealed a uctuation infrequencies of mycorrhizal apices between13.1% <strong>and</strong> 86% during the same period.One of our ndings during the study is thedominance of C. geophilum morphotype, aresult shared with other similar studies. Gerhardtet al. (2007) found that this is the dominatingmorphotype in 80% of the investigated<strong>Quercus</strong> rubra st<strong>and</strong>s also the most abundantmycorrhiza forming mycobiont on the rootsof <strong>Quercus</strong> garryana (Valentine et al. 2004).C. geophilum is a pioneer stage mycorrhizalpartner but, also a late stage, being present

Fodor et al. Mycorrhizal status of several <strong>Quercus</strong> species in <strong>Romania</strong> ...in seedling mycorrhizae as well as in maturetrees’ roots (Piggott 1982, Kranabetter &Wylie 1998) associating with 122 host species(Trappe 1964). The outer layer of the mantleconsists of thick walled cells, resembling thegelatinous walls of many lichenicolous fungi.When wet, these walls become gelatinous,providing an environment for water storage,which is of capital importance during thedrought episodes. This pecularity gives an advantageto seedlings possessing C. geophilummycorrhiza (Piggot 1982). Being ubiquitous bynature, C. geophilum links plants in a commonmycorrhizal network (Valentine at al. 2004). Itis an early stage <strong>and</strong> also a late stage associatein seral succession of the forests. Late stagefungi, such as Lactarius spp. <strong>and</strong> Russula spp.are infrequent on roots <strong>and</strong> the inoculationproduces via root connections, rather than bymycelial fragments or spores as in early stagemycorrhiza (Jones et al. 1998).The association of different morphotypes ismore or less r<strong>and</strong>om, with respect to closelyrelated hosts in the same location <strong>and</strong> showrelatively high similarity between locationsrelated to the same host species. Still the nullhypothesis of r<strong>and</strong>om association is to be carefullyveried on larger sets of data. The generaltrend is a variation of morphotypes, accordingto geographical factors (Southern versusNorth-Western <strong>Romania</strong>) <strong>and</strong> also to relatedhosts allocation (<strong>Quercus</strong> spp.). There is anevidence of within site partition of the samemorphotypes among <strong>Quercus</strong> hosts <strong>and</strong> similarityof sites from same geographical area. Itis worth to mention the dissimilarity in morphotypeallocation in Q. <strong>robur</strong> as compared toQ. <strong>cerris</strong> <strong>and</strong> Q. <strong>frainetto</strong>.Stressful conditions affect trees in urban areas,a fact reected in their mycorrhizal status,<strong>and</strong> in lower frequency of mycorrhizal apices.Also, carpophore production is a seldom eventin urban areas (Danielson & Pruden 1989, Baxteret al. 1999) never observed in present survey(from 1997 to 2008) in the city of Oradea.Drought <strong>and</strong> oil pollution reported from Tincainuenced the mycorrhizal status of Q. <strong>cerris</strong><strong>and</strong> Q. <strong>frainetto</strong>, reected in low frequenciesof mycorrhizal apices.Modern investigations on the diversity ofmycorrhiza, associated with a particular treehost, rely on DNA nger-printing. This diversityassessment takes into account all potentialmycobionts associated with a tree <strong>and</strong> notthose active at a particular moment. For activemycorrhiza at a time snapshot, the classical assessmentbased on morphotypes is a better approachon our opinion based on the presentedresults.These results lead to the idea that articialinoculation with site-adapted mycobiontswould enhance plant growth <strong>and</strong> survival afteroutplanting, an opinion shared with otherauthors (e.g. Gerhardt et al. 2007). The mycorrhizationis induced either under laboratoryconditions on dual host-fungus systems, eitherduring the seedlings growth by inoculation ofthe fungal inoculum in nursery containers, theinoculum being represented by spores, myceliaor simply, fragments of appropriate carpophores(Martinez-Amores et al. 1991). The micropropagatedplantlets of <strong>Quercus</strong> species canbe exposed to mycobionts in order to inducemycorrhization. In our opinion, a good c<strong>and</strong>idateis Cenococcum geophilum, due to its largeecological <strong>and</strong> host range, <strong>and</strong> the capacity toinduce frequent mycorrhizal tips, a hypothesisworth to test under experimental conditions.As a consequence, it is a good c<strong>and</strong>idate formycorrhization in dual systems (oak microcuttingsor micropropagated plants + mycobiont)in Petri dishes, a similar approach being proposedby Herrmann et al. (1998).ConclusionThe investigation of mycorrhizae using theclassical approach of morphotype descriptionyielded 30 types common for <strong>Quercus</strong> <strong>robur</strong>,Q. <strong>cerris</strong>, Q. <strong>frainetto</strong>. The original descriptionsof the morphotypes provide a recognition69

Ann. For. Res. 54(1): 57-71, 2011tool, to be used in further studies on <strong>Quercus</strong>spp. mycorrhizae, Cenoccocum geophilum beingthe exception of the already described morphotypeby Agerer (1987-2002).Although the number of described morphotypesis relatively high, at a specic timesnapshot there are fewer, around 14 activemorphotypes. Most frequently encountered<strong>and</strong> dominating mycobiont, under normal<strong>and</strong> stressful conditions, was Cenococcumgeophilum, a good c<strong>and</strong>idate for in vitro mycorrhization<strong>and</strong> further acclimatization of theplantlets. However, there is a geographical <strong>and</strong>host dependent pattern for the association ofdifferent morphotypes, as our study reveals. 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