Spread of plant pathogens and insect vectors at the northern range margin of cypress in Italy

The Mediterranean cypress (Cupressus sempervirens) is a multi-purpose tree widely used in the Mediterranean region. An anthropogenic range expansion of cypress has taken place at the northern margin of the range in Italy in recent decades, driven by ornamental planting in spite of climatic constraints imposed by low winter temperature. The expansion has created new habitats for pathogens and pests, which strongly limit tree survival in the historical (core) part of the range. Based on the enemy release hypothesis, we predicted that damage should be lower in the expansion area. By comparing tree and seed cone damage by pathogens and pests in core and expansion areas of Trentino, a district in the southern Alps, we showed that tree damage was significantly higher in the core area. Seed cones of C. sempervirens are intensively colonized by an aggressive and specific pathogen (the canker fungus Seiridium cardinale, Coelomycetes), associated with seed insect vectors Megastigmus wachtli (Hymenoptera Torymidae) and Orsillus maculatus (Heteroptera Lygaeidae). In contrast, we observed lower tree damage in the expansion area, where a non-aggressive fungus (Pestalotiopsis funerea, Coelomycetes) was more frequently associated with the same insect vectors. Our results indicate that both insect species have a great potential to reach the range margin, representing a continuous threat of the arrival of fungal pathogens to trees planted at extreme sites. Global warming may accelerate this process since both insects and fungi profit from increased temperature. In the future, cypress planted at the range margin may then face similar pest and pathogen threats as in the historical range.     

Phytophthora-Stammbasisfäule an Dieffenbachia maculate (Erreger: P. mexicana Hots. et Hart.)

Stem base rot of Dieffenbachia maculata caused by Phytophthora mexicana During the last years a stem rot of Dieffenbachia maculata (Lodd.) G. Don has been observed in greenhouses of several commercial nurseries, located in different parts of the Federal Republic of Germany. The disease partly caused heavy losses. From all diseased plant parts (stem base, petiole and root) the same fungus could be isolated. It was diagnosed as Phytophthora mexicana Hots, et Hart., which is closely related to P. palmivora (Butl.) Butl. Apparently the former species is recorded for the first time as the causal organism of a Dieffenbachia stem rot and also for the first time in Europe. It is supposed that the fungus was imported to Germany via the Netherlands because all plants had been bought there, which diseased later.     

A new Ophiostoma species isolated from the ambrosia beetle Xyleborus dryographus (Coleoptera: Scolytidae)

An undescribed ophiostomatoid fungus was isolated from the scolytid beetle Xyleborus dryographus in south-west Germany. The fungus is described as Ophiostoma verrucosum sp. nov. with a Hyalorhinocladiella anamorph. The teleomorph is characterized by thick-sheathed ascospores, numerous divergent ostiolar hyphae and an ornamented perithecial base.     

Three rare and little known cryptogonimid digeneans from the sciaenid fish Sciaena umbra (L.) in the western Mediterranean

Three species of cryptogonimid digeneans are redescribed from the gut of Sciaena umbra off Corsica. The systematics of the three species, Metadena pauli (Vlassenko, 1931), Paracryptogonimus aloysiae (Stossich, 1885) n. comb. and Anoiktostoma coronatum (Wagener, 1852), are discussed. The latter two species, which have not been reported for more than 100 years, have previously been confused and synonymised with each other. P. aloysiae, which is transferred to Paracryptogonimus from Anoiktostoma, is restricted to the rectum, whereas A. coronatum prefers the pyloric caeca and anterior intestine.     

Four closely related but forgotten species of Rhipidocotyle Diesing, 1858 (Digenea: Bucephalidae) in fishes from European seas

The following species of Rhipidocotyle are described: R. minima (Wagener, 1852) from Chelidonichthys gurnardus, C. lastoviza and Aspitrigla cuculus at various localities off the British Isles; R. nicolli n. sp. from A. cuculus off Plymouth, SW England; R. triglae (van Beneden, 1870) from C. lucernus in the Gulf of Marseilles, western Mediterranean; and R. viperae (van Beneden, 1870) from Echiichthys vipera at various localities off the British Isles. The distinguishing features of the species are discussed in detail. A list of the bucephalid species reported from the Mediterranean Sea is appended.     

Cystobasidiopsis nirenbergiae, a new agaricostilbomycete (Pucciniomycotina)

A new genus, Cystobasidiopsis, and a new species, Cystobasidiopsis nirenbergiae, are described for a fungus isolated from an arable loess soil in Ahlum near Braunschweig, Niedersachsen, Germany. An integrated analysis of morphological, ecological, ultrastructural and molecular data indicates that the new species belongs to the Chionosphaeraceae within the Agaricostilbales. Relevant characteristics of the new species are discussed and compared with those of related taxa.     

Interaction Of Barley Yellow Dwarf Virus and Fusarium culmorum (W. G. Sm.) Sacc. in Winter Wheat

The barley yellow dwarf virus (BYDV) epidemics, which occurred predominantly in northern Germany in 1988–90 and caused unusual yield losses of wheat, prompted our study on interactions of BYDV and Fusarium culmorum. At the late stages of plant development (EC 55/65) infections with BYDV resulted in a lower yield reduction of wheat plants than infections with F. culmorum. Combined infections at flowering resulted in severer yield reduction, indicating additive effects of the two pathogens. However, if wheat infected by BYDV at stage EC 25/35 was secondarily inoculated with the fungus at EC 55/65 the yield was less reduced than in combined infections at EC 55/65. Our results proved that the susceptibility of wheat plants to F. culmorum is increased when infection by BYDV takes place during the late stages of growth. These results correspond to observations during 3 years of the epidemic in Germany. In these years BYDV was spread mainly during the late spring, resulting in a severe secondary infection by the fungus. From the results of these investigations it may be concluded that during the years of BYDV epidemic the yield of wheat was reduced to an economically important extent because of the fungal infection, which was favoured by the virus infection.     

Interactions Between Hyphosphere-Associated Bacteria and the Fungus <Emphasis Type="Italic">Cladosporium herbarum</Emphasis> on Aquatic Leaf Litter

We investigated microbial interactions of aquatic bacteria associated with hyphae (the hyphosphere) of freshwater fungi on leaf litter. Bacteria were isolated directly from the hyphae of fungi from sedimented leaves of a small stream in the National Park “Lower Oder,” Germany. To investigate interactions, bacteria and fungi were pairwise co-cultivated on leaf-extract medium and in microcosms loaded with leaves. The performance of fungi and bacteria was monitored by measuring growth, enzyme production, and respiration of mono- and co-cultures. Growth inhibition of the fungus Cladosporium herbarum by Ralstonia pickettii was detected on leaf extract agar plates. In microcosms, the presence of Chryseobacterium sp. lowered the exocellulase, endocellulase, and cellobiase activity of the fungus. Additionally, the conversion of leaf material into microbial biomass was retarded in co-cultures. The respiration of the fungus was uninfluenced by the presence of the bacterium.     

New Races of Sunflower Downy Mildew (Plasmopara Halstedii) in Germany

Plasmopara halstedii, the causal agent of downy mildew of cultivated sunflower (Helianthus annuus), was documented in Germany for the first time in commercial fields. The pathogen was first observed in the Württemberg area, where races 1 and 4 were identified using a set of differential lines. Later, commercial fields near Baden were found to be infected by race 5, which is the first occurrence of that race outside of North America. With the discovery of race 5, there are now eight races of the sunflower downy mildew fungus that have been found in Europe. The sunflower cultivars most frequently grown in Germany were investigated for resistance to race 1, 4 and 5; while all were resistant to race 1, none were resistant to either race 4 or 5.     

New Races of Sunflower Downy Mildew (Plasmopara Halstedii) in Germany

Plasmopara halstedii, the causal agent of downy mildew of cultivated sunflower (Helianthus annuus), was documented in Germany for the first time in commercial fields. The pathogen was first observed in the Württemberg area, where races 1 and 4 were identified using a set of differential lines. Later, commericial fields near Baden were found to be infected by race 5, which is the first occurrence of that race outside of North America. Withthe discovery of race 5, there are now eight races of the sunflower downy mildew fungus that have been found in Europe. The sunflower cultivars most frequently grown in Germany were investigated for resistance to race 1, 4 and 5; while all were resistant to race 1, none were resistant to either race, 4 or 5.     

Molecular genetic determinants of intraspecific polymorphism of the phytopathogenic fungus <Emphasis Type="Italic">Cryphonectria parasitica</Emphasis>

The review summarizes the current evidence on the phytopathogenic fungus Cryphonectria parasitica, which is a classic object for studying hypovirulence. Phenotypic manifestations of hypovirulence and the molecular mechanisms of action of the mycovirus Cryphonectria hypovirus (CHV) infecting the fungus are described in detail. Genetic determinants of vegetative incompatibility in C. parasitica (a phenomenon increasing polymorphism of the fungus and preventing CHV expansion) are considered. The data on C. parasitica polymorphism are correlated with the data on the distribution of different CHV species in the European, American, and Asian populations of the fungus.     

Fusarium Species Colonizing Spears and Forming Mycotoxins in Field Samples of Asparagus from Germany and Poland

The occurrence of Fusarium spp. and associated mycotoxins in asparagus spears was evaluated in Poland in 2002 and 2003 and in Germany in 2002. Spears of two cultivars, Eposs and Gijnlim, were collected from two locations in Poland, Swidwowiec and Poznan, on sandy and sandy loam soil, respectively. Fusarium oxysporum and F. proliferatum were detected at an average incidence of 38.3% and 15.8% in the spear sections sampled, respectively. In stands of 11 (tested) cultivars of asparagus sampled in Germany on sandy soil, the same species dominated, however, they were less frequent than in Poland (26.6% and 5.6% of the spears infected with F. oxysporum and F. proliferatum, respectively). Chemical analyses revealed that fumonisin B₁ (FB₁) and moniliformin (MON) were present in some of the spears sampled in Poland. FB₁ was not found and MON was not assessed in spears sampled in Germany in 2002, but F. proliferatum was able to form the toxin in vitro in the range from 101.4 up to 205.8 μg/kg maize kernel substrate. Asparagus samples in Poland contained FB₁ at up to 5.6 μg/kg spear fresh weight. The highest MON concentration (1350 μg/kg) was detected in cultivar Eposs in Marcelin, Poland, in 2002. MON and FB₁ were found in spears infected by both F. oxysporum and F. proliferatum, however, only the latter fungus was able to synthesize both toxins.     

Photoinhibition and Recovery of Photosynthesis in Canker-susceptible and Resistant Needles of Cypress (Cupressus sempervirens L.)

The aim of the present investigation was to test the hypothesis that the cypress canker caused by a fungus (Seiridium cardinale) infection induced effects on photosynthesis which could be related to photoinhibition and the process of recovery in susceptible and resistant needles. Photoinhibition of photosynthesis and recovery was studied in canker‐infected susceptible and resistant needles of cypress (Cupressus sempervirens L.) under controlled conditions (irradiation of detached needles to approximately 1900 μmol/m²/s). The degree of photoinhibition was determined by means of the ratio of variable to maximum chlorophyll (Chl) fluorescence (F_v/F_m) and electron transport measurements. The potential efficiency of photosystem (PS) II, F_v/F_m declined, and F_o increased significantly in canker‐susceptible needles, while F_o did not change in resistant needles. In isolated thylakoids, high light (HL) decreased the rate of whole chain and PS II activity markedly more in susceptible than in resistant needles. A smaller reduction of PS I activity was noticed only in susceptible needles. Upon subsequent dark incubation, fast recovery was noticed in both needle types and reached maximum rates of PS II efficiency similar to those noticed in non‐photoinhibited needles. The artificial exogenous electron donors such as diphenyl carbazide (DPC), NH₂OH and Mn²⁺ failed to restore the HL induced loss of PS II activity in susceptible needles, while DPC and NH₂OH significantly restored it in resistant needles. The results suggest that HL inactivates the donor side of PS II in resistant and the acceptor side of PS II in susceptible needles. The results on the quantification of the PS II reaction centre protein D1 and 33 kDa protein of water‐splitting complex following HL exposure showed pronounced differences between susceptible and resistant needles. The marked loss of PS II activity in HL‐irradiated needles was due to the marked loss of D1 protein in susceptible and 33 kDa protein in resistant needles, respectively.     

Digestive capacities of leaf-cutting ants and the contribution of their fungal cultivar to the degradation of plant material

Leaf-cutting ants (tribe Attini) are a unique group of ants that cultivate a fungus that serves as a main source of their food. The fungus is grown on fresh leaves that are harvested by workers. We examine the respective contribution of ants and their symbiotic fungus in the degradation of plant material by examining the digestive capacities of seven Attini species in the genera Atta and Acromyrmex. The results show that both, the ants and their mutualistic fungi, have complementary enzymatic activities. Ants are specialized in the degradation of low molecular weight substrates (oligosaccharides and heterosides) whereas the fungus displays high polysaccharidase activity. The two genera Atta and Acromyrmex are not distinguished by a specific enzymatic activity. The seven different mutualistic associations examined display a similar enzymatic profile but have quantitative differences in substrate degradation activities. The respective contribution of ants and the fungus garden in plant degradation are discussed.     

Structural characterization of the O-chain polysaccharide from an environmentally beneficial bacterium Pseudomonas chlororaphis subsp. aureofaciens strain M71

Pseudomonas chlororaphis subsp. aureofaciens strain M71 was isolated from the root of a tomato plant and it was able to control in vivo Fusarium oxysporum f. sp. radicis-lycopersici responsible for the tomato crown and root rot. Recently, strain M71 was evaluated even for its efficacy in controlling Seiridium cardinale, the causal agent of bark canker of common cypress (Cupressus sempervirens L.). Strain M71 ability to persist on the tomato rhizosphere and on the aerial part of cypress plants could be related to the nature of the lipopolysaccharides (LPS) present on the outer membrane and in particular to the O-specific polysaccharide.A neutral O-specific polysaccharide was obtained by mild acid hydrolysis of the lipopolysaccharide from P. chlororaphis subsp. aureofaciens strain M71. By means of compositional analyses and NMR spectroscopy, the chemical repeating unit of the polymer was identified as the following linear trisaccharide.     

Parasitic microfungi of the Tatra Mountains. 3. <Emphasis Type="Italic">Spermosporina gymnadeniae</Emphasis> (Hyphomycetes): species new to Slovakia and new records from Poland

Spermosporina gymnadeniae (Hyphomycetes) on Gymnadenia sp. (Orchidaceae) collected in the Polish part of the Tatra Mts was described in 2003. The fungus was recently found at new localities in Poland and Slovakia. It was recorded on Gymnadenia conopsea s.l. and Dactylorhiza fuchsii, which are new hosts of this parasite. The fungus is described and additional illustrations are provided.     

Trimmatostroma abietis sp. nov. (hyphomycetes) and related species

Trimmatostroma abietis from the needles of conifers and from stone, mostly in Germany, is described. On the natural substrate it is characterized by stromatic conidiomata. Conidia are mostly two-celled, are arranged in long chains, and originate by intercalary dilatation of fertile hyphae. The wide morphological plasticity of the fungus and its physiological profile are described. Its occurrence as a saprophyte and possibly opportunistic pathogen on plants and as an invader of environments with low water activity, particularly stone surfaces, are discussed. Relationships with other taxa are outlined.     

A new acidophilic fungus Teratosphaeria acidotherma (Capnodiales, Ascomycota) from a hot spring

A novel acidophilic fungus was isolated by an acidic enrichment culture of microbial mats and biofilms collected at an extremely acidic and high temperature hot spring. In culture studies, this fungus was revealed to produce ascomycetous teleomorph structures. Molecular phylogenetic study and morphological observation showed this fungus is a new species of the genus Teratosphaeria (Capnodiales, Dothideomycetes) and is phylogenetically close to Acidomyces acidophilus and Bispora sp., which were previously reported as acidophilic anamorphic fungi. This new fungus is described here as a new species of Teratosphaeria, and its physiological properties adapting to its habitat are demonstrated. This is the first report of a teleomorphic fungus having highly acidophilic and thermophilic properties.     

Attraction and oviposition responses of the fungus gnat Bradysia impatiens to microbes and microbe‐inoculated seedlings in laboratory bioassays

Laboratory tests were conducted to examine preferences of Bradysia impatiens Johannsen (Diptera: Sciaridae) larvae and adults for various microbes associated with greenhouse crops. Fungus gnat larvae and adults exhibited a preference for cultures of Pythium spp. over the medium used to grow the pathogens. Larvae also exhibited a preference for geranium seedlings infected with pathogenic Pythium spp. [P. aphanidermatum (Edson) Fitz., P. ultimum Trow, and P. irregulare Buis. (Oomycota: Peronosporales)] over non‐inoculated plants. Adult fungus gnats exhibited a strong ovipositional preference for the aforementioned Pythium spp. as well as a variety of other microorganisms, including the pathogenic fungus Thielaviopsis basicola (Berk. & Br.) (Ascomycota: Microascales), the geranium‐infecting bacterium Xanthomonas campestris pv. pelargonii (Brown) Dye (Proteobacteria: Xanthomonadales), the non‐pathogenic species Pythium torulosum Coker & P. Patt. and Pythium graminicola Subramaniam, the pathogen‐suppressive fungus Trichoderma harzianum Rifai (Ascomycota: Hypocreales), and the insect pathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales). Our study is the first to demonstrate that fungus gnats are attracted to and/or stimulated to oviposit by a wide array of living microorganisms both in pure culture and in association with plant seedlings. These findings have important implications with respect to the potential role of fungus gnats in plant pathogen transmission.     

CONTRIBUTIONS TO OUR KNOWLEDGE OF AMBROSIA FUNGI. II. ENDOMYCOPSIS FASCICULATA NOM. NOV. (ASCOMYCETES)

Hatha , Lekh R. (U. Kansas, Lawrence.) Contributions to our knowledge of ambrosia fungi. II. Endomycopsis fasciculat nom. nov. (Ascomycetes). Amer. Jour. Bot. 50(5): 481–487. Illus. 1963.—Endomyceu bispora Verrall (1943) is a later homonym of E. bisporus Beck (1922) (= Endomycopsis bispora [Beck] Dekker), and the former is now described under the new name Endomycopsis fasciculata Batra. The ambrosia beetle Gnathotrichus materiarius (Fitch) lives symbiotically with Endomycopsis fasciculata which serves as the major source of food for the larvae and probably for the adults. The fungus forms an extensive palisade lining throughout the larval or pupal cells and the main tunnel dug by the mother. All stages of the fungus can be obtained from the same tunnel and the fungus seems to be homothallic. The asci are typically 2-spored and aseosporcs are eucullate. The fungus does not assimilate nitrate as the sole source of nitrogen. Detailed morphology and nutritional requirements of E. fasciculata are discussed.