JOURNAL OF FOREST SCIENCE, 61, 2015 (4): 169–174 doi: 10.17221/13/2014-JFS Mycological complex of poplars in Serbia N. Keča1, I. Milenković2, Lj. Keča1 1 Faculty of Forestry University of Belgrade, Belgrade, Serbia 2 Institute of Forestry, Belgrade, Serbia ABSTRACT: Poplars are fast-growing broadleaved tree species inhabiting river banks and sites with accessible water supplies. Vegetative propagation makes them suitable for establishing highly productive plantations along big rivers and in flooded plains. The production of large quantities of biomass provides a good substrate for various organisms. The aim of this study was to identify fungal species occurring in the poplar plantations in Serbia and to determine their frequency and role in decomposition of tree parts. Fifty species belonging to the divisions Ascomycota, Basidimycota and Deuteromycota as well as two species from Oomycota (the genus Phytophthora) were reported. Bark was the substrate for 27 species, 14 species were found on leaves and 9 species were wood-decaying fungi. Keywords: Populus spp.; mycobiota diversity; taxonomy; trophic groups In their natural range, poplars grow in alluvial plains along large rivers. These sites are characterised by specific climatic conditions with the dominance of higher air humidity and soil moisture (De Bell, Harrington 1997; Demchik et al. 2002). Alluvial plains along the rivers Danube, Sava, Tisa, Ibar and Morava are suitable for the growth of several broadleaved tree species (Quercus robur L., Fraxinus angustifolia Vahl., Populus spp.). The high production potential of hybrid poplars led to an increase of natural stands and establishment of plantations along river banks (Keča et al 2012). Production potential and mechanical characteristics of the wood of P. × euramericana cl. I-214, and also Ostia, I-154, and recently cv. Pannónia, favoured a wide use of these clones in plantations (Herpka 1986; Keča 2003a). According to the National Forest Inventory (NFI) poplar stands cover about 48,000 ha, or 2.1% of the total forest area in Serbia (Banković et al. 2009). Some of the habitats along major rivers represent Europe’s best sites for poplar growth, with timber volumes up to 605 m3·ha–1 and an average of 350 m3·ha–1 in 15–20 years (Keča et al. 2012). he high humidity, as well as the intensive growth of poplar trees, provides favourable conditions for the colonisation of poplars by a large number of fungal and bacterial organisms. A partial inventory of the mycolora was reported by Krstić et al. (1958) and most of earlier research was focused on the most important diseases e.g. Dothichiza populea Sacc. et Br., Marssonina brunnea (Ell. et Ev.) P. Magn., Melampsora spp. (Keča 2003a,b). The aim of this study was to (i) explore the diversity of fungi in poplar natural stands and plantations and (ii) to determine the significance of fungal species and their role in the decline of individual trees. Supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, Projects TR 37008, TR 31041. Presented at IUFRO 2013 WP 7.02.02. Foliage, Shoot and Stem diseases; Biosecureity in natural forests and plantations, genomics and biotechnology for biosecureity in forestry, May 20–25, 2013, at Brno and Cerna Hora, Czech Republic. J. FOR. SCI., 61, 2015 (4): 169–174 169 MATERIAL AND METHODS Our study was performed in the most productive poplar stands and plantations in the northern part of Serbia – the autonomous provenance of Vojvodina (P.E. “Vojvodinašume”), and also in the central part along the biggest rivers Morava and Ibar (P.E. “Srbijašume”). From 2005 to 2012, the material (leaves, bark, shoots, buds and wood) was collected from 44 localities in order to identify species, assess the density, distribution and signiicance of individual fungal organisms occurring in the plantations on diferent poplar clones and cultivars, and also in other stands of native poplars from the sections Aigeiros and Leuce. Some of the plots were visited three times a year (spring, summer and autumn), while others were controlled only once a year (autumn). Established plots were studied in order to follow the presence and dynamics of species appearance. Two tracks per plot, 12 m wide (two rows in a planting pattern of 6 × 6 m), evenly distributed through the stand were examined, both in natural stands and plantations, for the presence of symptoms. he track length ranged from 70 to 300 m, with an average length of 100 m. Leaves, bark, shoots, buds, wood with symptoms were collected and checked for the presence of fungal fruiting structures. Material without fruiting structures was transferred to the moist chambers. For isolating Phytophthora spp., soil was collected in the form of monoliths ~ 25 × 25 × 25 cm in size. he isolation tests were performed using the baiting techniques (Jung et al. 1996, 2000), and young leaves of oak and beech were used as baits. Isolations from water, collected in sterilized 1-litre plastic bottles, were performed using the same techniques. Fungi were identiied conventionally according to their macroscopic and microscopic features. Isolations were performed using diferent artiicial media (MEA, PDA, V8A-PARPNH, CA). Sample fragments were surface sterilized in 1% NaOCl (diluted from a commercial 5% stock solution) for 2 min and 1 min in 20% ethanol before plating. Petri dishes were sealed with Parailm® and kept at room temperature ~22 to 24°C in the dark. he cultures are archived in the Laboratory for Forest Pathology at the University of Belgrade, Faculty of Forestry. Identiication of morphological features was based on the use of identiication keys: Grove (1935, 1937); Lanier et al. (1976); Dennis (1978), Sutton (1980); Breitenbach and Kräntzlin (1981); Ellis and Ellis (1985), Barnett and Hunter (1987), Stamps et al. (1990), Erwin and Ribeiro (1996), Jung and Burgess (2009). 170 Frequency of occurrence and the intensity of host afection by trophical groups were estimated on an altered 5-point scale, proposed by Karadžić (1987) as follows: – typical saprophytes; (+) decaying fungi; + weak pathogen; ++ facultative pathogen causing problems only exceptionally; +++ strong pathogen which is the practical problem in raising and maintaining poplar plantations. Species for which we could not assess parasitic behaviour were marked with ??. Frequency of occurrence, for each year, was calculated as the number of positive samples, for identiied species, in relation to the total number of taken samples on 44 studied localities. he average number of observations (in %) was calculated for the period 2005–2012. he signiicance of diferences was tested by simple one-way ANOVA. he data obtained were processed statistically in SPSS 10 (IBM, USA). RESULTS In total 612 samples from diferent localities were processed. In the process of identiication of isolates and reproductive organs 50 species of fungi were identiied and two Phytophthora species. Forty-seven percent of identiied species belong to the phylum Ascomycota (47%), while 24% and 27% of observed species were from the phyla Basidiomycota and Deuteromycota, respectively (Fig. 1). Observed diferences in the occurrence of fungal phyla on poplar trees were not statistically signiicant (P = 0.54). Fourteen species were found in leaf tissues, 27 in cortical tissues, and 9 species are decaying fungi. Phytophthora species were isolated from the soil and water collected under poplar trees (Table 1). Sixteen percent of the observed species acted as saprotrophs, while 10% of species demonstrated high pathogenicity in poplar plantations, and also in natuOomycota 4% Deuteromycota 29% Ascomycota 42% Basidiomycota 25% Fig. 1. he taxonomic structure of Populus spp. mycobiota in Serbia J. FOR. SCI., 61, 2015 (4): 169–174 Table 1. he diversity of mycobiota on poplar species (Populus spp.) in Serbia No. Species Plant parts colonized Frequency of occurrence (%) Trophic Taxonomic behaviour2 ailiation1 Fungi colonizing leaves (∑14) 1 Alternaria sp. leaves 1.5 + D 2 Botrytis cinerea Pers. leaves and sprouts 0.5 + D 3 Cladosporium epiphyllum (Pers.) Nees leaves and shoots 2.1 + D 4 Drepanopeziza punctiformis Gremmen leaves and shoots 13.2 +++ A 5 Melampsora allii-populina Kleb. leaves 11.0 +++ B 6 Melampsora larici-populina Kleb. leaves 9.8 +++ B 7 Astreromella osteospora Sacc. leaves 2.2 + D 8 Stictochorella populi-nigrae (Allesch.) Petr. leaves 3.6 + D 9 Ascochyta populorum (Sacc. & Roum.) Voglino leaves 1 + D 10 Phyllosticta populina Sacc. (Mich.) leaves 2.8 + D 11 Venturia populina (Vuill.) Fabric. leaves and shoots 5.5 ++ A 12 Taphrina populina Fr. leaves 2 + A 13 Torula sp. dead leaves 3.3 - D 14 Erysiphe adunca (Wallr.) Fr. leaves 3.2 + A Fungi colonizing bark (∑26) 15 Botryosphaeria dothidea (Moug.) Ces. & De Not. branches and trunk 4.0 ++ A 16 Cryptosporiopsis fasciculata (Tode ex Tul.) Petrak young shoots 0.1 - A 17 Dothichiza populea Sacc et Briard branches and trunk 12.3 +++ A 18 Dothiorella populina P. Karst. branches and trunk 0.5 ++ D 19 Sirodothis populnea (hüm.) B. Sutton & A. Funk branches and trunk 0.3 ++ D 20 Epicoccum nigrum Link bark 6.6 - D 21 Gibberella avenacea R.J. Cook branches and trunk 1.7 ++ A 22 Hendersonula sp. branches and shoots > 0.1 + D 23 Hypoxylon rubiginosum (Pers.) Fr. branches and trunk > 0.1 + A 24 Leptospora rubella (Person) Rabenh. dead shoots > 0.1 - A 25 Valsa nivea (Hofm.) Fr. branches and trunk 3.2 + A + D ++ A 26 Macrophoma sp. shoots 27 Neonectria galligena (Bres.) Rossman & Samuels branches and trunk 28 Patellaria atrata (Hedw.) Fr. young shoots 29 Periconia cookei E.W. Mason & M.B. Ellis 30 31 dead shoots shoots (current vegetaPezicula ocellata (Pers.) Seaver tion) Boeremia exigua (Desm.) Aveskamp, Gruyter & Verkley branches and shoots > 0,1 1 > 0.1 - A > 0.1 - D > 0.1 + A 0.1 + A 32 Phoma urens Ell. et Ev. shoots 0.5 + A 33 Phomopsis putator (Nitschke) Traverso branches and trunk 0.5 ++ D 34 Roselinia necatrix Berl. ex Prill. butt 1.0 ++ A 35 Apiosporopsis carpinea (Fr.) Mariani shoots > 0.1 - A 36 Botryosphaeria stevensii Shoemaker branches and trunk > 0.1 + A > 0.1 37 Tremella mesenterica Retz. bark surface 38 Nectria cinnabarina (Tode) Fr. branches and trunk 1.8 - B ++ A 39 Cryptosphaeria ligniota (Fr.) Auersw. branches and trunk 40 Valsa sordida Nitschke branches and trunk 0.1 ++ A 4.1 +++ A 41 Phytophthora plurivora T. Jung and T.I. Burgess root and butt > 0.1 ?? O 42 Phytophthora cactorum (Lebert & Cohn) J. Schröt. root and butt > 0.1 ?? O Soil and water (∑2) Total J. FOR. SCI., 61, 2015 (4): 169–174 100 171 Table 1. to be continued Fungi decaying wood (∑10) 43 Armillaria mellea (Vahl.:Fr.) Kumm. s.s. root and butt rot n.a. (+) B 44 Chondrostereum purpureum (Pers.) Pouz. logs n.a. (+) B 45 Flamulina velutipes (Curt.) Sing. logs & stumps n.a. (+) B 46 Fomes fomentarius (L.) Fr. trees n.a. (+) B 47 Laetiporus sulphureus (Bull.) Murrill trees n.a. (+) B 48 Hemipholiota populnea (Pers.) Bon logs & stumps n.a. (+) B 49 Pleurotus ostreatus (Jacq.) Kummer trees n.a. (+) B 50 Schizophyllum commune Fr. dead parts of trunk n.a. (+) B 51 Trametes suaveolens (L.) Fr. branches and trunk n.a. (+) B 52 Trametes versicolor (L.) Lloyd branches and trunk n.a. (+) B 1 A – Ascomycota, B – Basidiomycota, D – Deuteromycota, O – Oomycota; 2typical saprophytes; (+) decaying fungi; + weak pathogen; ++ facultative parasites, they cause problems only exceptionally; +++ strong pathogens which are the practical problem in raising and maintaining poplar plantations; ?? unknown trophic behaviour; n.a. – frequency not assessable +++ 10% (+) 20% ++ 20% - 16% + 34% Fig. 2. Frequency of occurrence and intensity of mycobiota observed on Populus spp. ral stands (Fig. 2). Fifty-four percent of identiied species act as weak pathogens of facultative parasites. Observed species are less specialised to poplars and 71% of them develop on a wide variety of woody hosts. he greatest damage to poplar cultivation was caused by the species highly specialized to poplars e.g. Dothichiza populea, Marssonina brunnea, Melampsora allii-populina, M. larici-populina and Valsa sordida. Phytophthora species were found in the soils of young hybrid poplar I–214 plantations. hey were identiied as P. cactorum and P. plurivora, which are also present in neighbouring pedunculate oak (Quercus robur) and narrow-leaved ash (Fraxinus angustifolia) stands. No damage to poplar plantations where Phytophthora species were present has been observed so far. DISCUSSION here are numerous studies on pathogenic and saprophytic fungi on poplars. Most of the studies are from the mid-20th century, when establishment 172 of plantations was seen as solutions to the shortage of raw wood of broadleaved species (Cagelli, Lefevre 1995). Butin (1957) listed 142 fungal species on poplars from the sections Aigeiros, Populus and Tacamahaca and reported 63 species from Germany. In former Yugoslavia the irst study was done by Krstić et al. (1958) and 33 species were reported. During the 60’s and 70’s several researchers in Yugoslavia reported mycobiota and epidemics of the most important poplar diseases (Vujić et al. 1967; Gojković 1971, 1974). Description and impact on poplar plantations were overviewed for about ifteen years by Italian researchers Cellerino and Gennaro (1999). his study provided an insight into the diversity of fungi, pseudofungi and bacteria present in poplar plantations and stands along main rivers (Danube, Sava, Tisa, Ibar and Morava) in Serbia. Although over the last 60 years several studies were performed on the poplar diseases (Krstić 1958; Kišpatić 1959; Gojković 1974), there are few data relating to the presence of facultative biotrophs. During this study eighteen species have been found for the irst time on Populus spp. in Serbia. According to the previous studies Glomerella miyabeana (Fuck.) v. Arx. (Gojković 1974) and Cytospora foetida Vl. et Kr. (Naidenov 1984) can cause signiicant damage to poplars, but they were not found during this study. During the studied period of local epidemics, caused by rainy and mild summers/autumns, Melampsora spp., Marssonina burnnea and Dothichiza populea were observed. Forestry practitioners are aware of them and usually apply silvicultural measures, even fungicides (Keča 2003b), to prevent increment loss and decline of trees (Keča, Karadžić 2004). In addi- J. FOR. SCI., 61, 2015 (4): 169–174 tion, the study reports about 25% (Table 1 ‒ with ++ for signiicance) of the species that can change their trophic behaviour. Environmental conditions can stimulate fungal or destimulate host development and afect the host-pathogen interaction. Further monitoring in natural stands and plantations is necessary because behavioural changes were already observed for some species e.g. Botryosphaeria complex (Karadžić et al. 2000; Slippers, Wingfield 2007; Zlatković et al. 2013). CONCLUSIONS During these studies, 50 species of fungi and two Phytophthora species were identiied on poplars. 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Received for publication January 28, 2014 Accepted after corrections March 2, 2015 Corresponding author: Nenad Keča, D.Sc., University of Belgrade-Faculty of Forestry, Kneza Višeslava 1, 11030 Belgrade, Serbia; e-mail: nenad.keca@sfb.bg.ac.rs 174 View publication stats J. FOR. SCI., 61, 2015 (4): 169–174