Slight dependence of temperate-forest herbaceous plants, Geum urbanum and Senecio ovatus, on arbuscular mycorrhizal fungi (AMF) enables them to colonise soils with a low level of AMF abundance.

While numerous studies have revealed that arbuscular mycorrhizal fungi (AMF) enhance plant performance, the influence of these symbionts on temperate-forest herbaceous species in relation to soil physical and chemical properties has been left largely unexplored. Therefore, two perennial herbs, Geum urbanum (Rosaceae) and Senecio ovatus (Asteraceae), were examined in a laboratory pot experiment to determine whether AMF influenced their growth, photosynthetic performance index, and N and P contents in biomass. The treatments, involving three widespread AMF species, were prepared in the soils of two habitats colonised by both plants, namely beech and riparian forests, as follows: (1) control-soils without AMF, (2) Claroideoglomus claroideum, (3) Funneliformis geosporus, and (4) Funneliformis mosseae. Neither shoot mass nor photosynthetic performance index of G. urbanum and S. ovatus was enhanced by AMF. Senecio ovatus root mass was increased compared to control only by F. geosporus. Inconsistent effects were observed in N and P contents in shoots and roots of both species. The direction and magnitude of these responses were dependent on the fungal species and soil type. Although the plant species belong to families whose representatives are usually regularly colonised by and highly responsive to AMF, our study indicates that AMF had only a slight impact on the performance of G. urbanum and S. ovatus at the early stages of their development. The plants being slightly dependent on AMF are thus adapted to colonise temperate-forest soils with a low level of availability of AMF propagules.

Neoerysiphe kerribeeensis sp. nov. (Ascomycota: Erysiphales), a new species of Neoerysiphe on native and introduced species of Senecio (Asteraceae) in Australia.

Anamorphic powdery mildew fungi on introduced taxa of Senecio and Pericallis × hybrida in Australia have previously been identified as Neoerysiphe cumminsiana on the basis of a combination of Euoidium-type conidiophores and lobed mycelial and germ tube appressoria. But, two specimens with chasmothecia on the indigenous Senecio glossanthus did not agree with published descriptions of N. cumminsiana. The teleomorph of the S. glossanthus mildew differed from that of N. cumminsiana in the morphology of its peridial cells, the pigmentation of its appendages, and the morphology and pigmentation of some secondary hyphae. Ribosomal DNA ITS sequences from the two S. glossanthus mildew specimens and five other specimens of Senecio mildews from south-eastern Australia demonstrated that all Australian Senecio mildews are conspecific and distinct from the northern hemisphere Senecio mildew (N. cumminsiana) and from other Neoerysiphe taxa. Based on morphological characters and rDNA sequence data, the Australian Senecio mildew is described as a new species, Neoerysiphe kerribeeensis. This is the first native teleomorphic powdery mildew described from Australia.

Species-specific effects of polyploidisation and plant traits of Centaurea maculosa and Senecio inaequidens on rhizosphere microorganisms.

Invasive plant species represent a threat to terrestrial ecosystems, but their effects on the soil biota and the mechanisms involved are not yet well understood. Many invasive species have undergone polyploidisation, leading to the coexistence of various cytotypes in the native range, whereas, in most cases, only one cytotype is present in the introduced range. Since genetic variation within a species can modify soil rhizosphere communities, we studied the effects of different cytotypes and ranges (native diploid, native tetraploid and introduced tetraploid) of Centaurea maculosa and Senecio inaequidens on microbial biomass carbon, rhizosphere total DNA content and bacterial communities of a standard soil in relation to plant functional traits. There was no overall significant difference in microbial biomass between cytotypes. The variation of rhizosphere total DNA content and bacterial community structure according to cytotype was species specific. The rhizosphere DNA content of S. inaequidens decreased with polyploidisation in the native range but did not vary for C. maculosa. In contrast, the bacterial community structure of C. maculosa was affected by polyploidisation and its diversity increased, whereas there was no significant change for S. inaequidens. Traits of S. inaequidens were correlated to the rhizosphere biota. Bacterial diversity and total DNA content were positively correlated with resource allocation to belowground growth and late flowering, whereas microbial biomass carbon was negatively correlated to investment in reproduction. There were no correlations between traits of the cytotypes of C. maculosa and corresponding rhizosphere soil biota. This study shows that polyploidisation may affect rhizosphere bacterial community composition, but that effects vary among plant species. Such changes may contribute to the success of invasive polyploid genotypes in the introduced range.

Putative natural hybrid between Puccinia lagenophorae and an unknown rust fungus on Senecio madagascariensis in KwaZulu-Natal, South Africa.

Several specimens of an aecial rust fungus were collected on Senecio madagascariensis during a field survey carried out in KwaZulu-Natal, South Africa. As telia were not present in the specimens collected, DNA sequence analyses were undertaken to determine the identity of the rust species. ITS and beta-tub1 sequencing confirmed that one of the isolates recovered is Puccinia lagenophorae sensu lato. On the other hand, sequencing and RFLP analysis revealed the presence of two divergent copies of ITS and beta-tub1 in all the other six isolates investigated. In both phylogenetic trees, one copy of the gene region grouped within a well supported clade with sequences of P. lagenophorae accessions from different geographical origins and hosts, and the Australian rusts Puccinia saccardoi and Puccinia stylidii. The other copy of these gene regions grouped within a separate clade comprising European accessions of Puccinia dioicae (ITS) and Uromyces sommerfeltii (beta-tub1) that occur on Asteraceae hosts. Multiple copies of these gene regions were not observed in Australian isolates of P. lagenophorae. Our study provides some evidence that an interspecific hybrid rust fungus, with P. lagenophorae as one of its parents, may occur on S. madagascariensis in South Africa. The identity of the other parent remains unknown.

Testing the evolution of increased competitive ability (EICA) hypothesis in a novel framework.

The "evolution of increased competitive ability" (EICA) hypothesis proposes that escape from natural enemies, e.g., after transcontinental introductions, alters the selection regime because costly defenses no longer enhance fitness. Such an evolutionary loss of defenses enables resources to be directed toward growth or other traits improving performance. We tested the EICA hypothesis in a novel framework in which the natural enemy is the traveler that follows its widespread host by accidental or deliberate (biocontrol) introductions. In a greenhouse experiment we used populations of Senecio vulgaris from North America, Europe, and Australia that differ in the history of exposure to the rust fungus Puccinia lagenophorae. Contrary to what is predicted by EICA, we found no evidence for increased levels of resistance to the rust fungus in plant populations with a longer history of rust exposure (Australia). Similarly, there was no evidence for reduced fecundity in these populations, although vegetative vigor, measured as secondary branching and growth rate, was lower. The maintenance of high rust resistance in populations with no (North America) or only a short history (Europe) of rust exposure is surprising given that resistance seems to incur considerable fitness costs, as indicated by the negative association between family mean resistance and fitness in the absence of disease observed for all three continents. The comparison of population differentiation in quantitative traits with estimates of differentiation in amplified fragment length polymorphic (AFLP) markers suggests that a number of fitness-related traits are under divergent selection among the studied populations. The proposed framework to test changes in the evolutionary trajectory underlying EICA can be employed in an expanded range of systems. These may include investigations on a cosmopolitan weed or crop when an antagonist is expanding its geographic range (such as our study), studies along a chronosequence of introduction time with expected increasing accumulation of natural enemies over time, or comparisons between introduced plant populations that differ in exposure time to biocontrol organisms.

Atividade antimicrobiana de Senecio heterotrichius DC. (Asteraceae) / Antimicrobial activity of Senecio heterotrichius DC.

Neste trabalho é relatada a avaliação da atividade antimicrobiana dos extratos diclorometânico e etanólico, obtidos por maceração das partes aéreas de S. heterotrichius pelo método de microdiluição em caldo, frente a patógenos bacterianos e fúngicos. O extrato diclorometânico evidenciou boa atividade inibitória frente a Candida krusei (CIM de 0,25 mg/mL) e moderada atividade frente a Staphylococcus aureus (CIM de 2,5 mg/mL). O extrato etanólico mostrou-se inativo frente aos microrganismos testados. Também foi isolado o constituinte majoritário do extrato diclorometânico, cuja análise espectroscópica indicou tratar-se de um sesquiterpeno, identificado como germacreno D.

This work describes the evaluation of the antimicrobial activity of CH2Cl2 and EtOH extracts obtained by the maceration of the aerial parts of Senecio heterotrichius DC. against bacterial and fungal pathogens by broth microdilution method. The CH2Cl2 extract showed the best activity against Candida krusei (MIC 0.25 mg/mL) and a moderate activity against Staphyllococcus aureus (MIC 2.5 mg/mL). The EtOH extract was inactive against the tested microorganisms. Besides, one of the main constituents of CH2Cl2 extract was isolated, and its spectroscopic analysis indicated the presence of a sesquiterpene identified as germacrene D.

Surveys of microfungi in a former industrial area in Duisburg-Nord.

One hundred and forty microfungi (Ascomycetes and Deuteromycetes) were collected in the "Landschaftspark Duisburg-Nord" located in North Rhine-Westphalia. New hosts for rarely found fungi are recorded for the first time. New for Germany are Massaria inquinans (Tode) De Not. and Nitschkia grevillei (Rhem) Nannf. on Acer pseudoplatanus L., Pirottaea nigrostriata Graddon on Artemisia vulgaris L., Ceratopycnis clematidis Höhn. on Clematis vitalba L., Dasyscyphus aff. humuli (W. Phillips) Dennis on Humulus lupulus L. and Leptosphaeria derasa (Berk. & Br.) Auersw. on Senecio inaequidens DC. New for North Rhine-Westphalia are Chaetosphaerella phaeostroma (Durieu & Mont.) E. Müller & Booth and Phomopsis platanoides (Cooke) Died. on Acer pseudoplatanus L., Microsphaeropsis pseudaspera Sutton, Mycosphaerella osborniae D. Hawksw. & Sivan. and Phomopsis oblita Sacc. on Artemisia vulgaris L., Leptosphaeria acuta (Fr.) P. Karst. and Leptosphaeria doliolum (Pers.) Ces. & De Not. on Bryonia dioica Jacq., Ophiobolus erythrosporus (Riess) G. Winter and Pleospora herbarum (Pers.) Rabenh. ex Ces. & De Not. on Dipsacus sylvestris (Huds), Keissleriella ocellata (Niessl) Bose on Hypericum perforatum L., Dactylaria aff. graminicola on Lolium perenne L., Siroplacodium aff. atrum on Oenothera beinnis L., Diatrypella favacea (Fr.) Sacc. on Prunus spec., Hapalosphaeria deformans (Syd.) Syd. and Microdiscula rubicola (Bres.) Höhn. on Rubus fructicosus agg. L., Cryptodiaporthe salicina (Pers.) Wehm. on Salix alba L. and Pleurophoma pleurospora (Sacc.) Höhn. on Salix caprea L.