Californian thistle (Cirsium arvense): endophytes and Puccinia punctiformis.

Californian thistle (Cirisum arvense) is a troublesome weed in pastures and cropping systems. The fungal biocontrol agent Puccinia punctiformis, commonly referred to as thistle rust, performs inconsistently on C. arvense. Problems with P. punctiformis establishment and control of C. arvense may be attributable to differing plant endophytic populations in various environments. This article provides an overview of the relationships between endophytes and their host, but also between endophytes and pathogens with a focus on rust pathogens. This review provides insights into reasons why P. punctiformis performs inconsistently and identifies gaps in our knowledge. Filling these gaps may help to improve performance of this classical fungal biocontrol agent. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Curvulin and Phaeosphaeride A from Paraphoma sp. VIZR 1.46 Isolated from Cirsium arvense as Potential Herbicides.

Phoma-like fungi are known as producers of diverse spectrum of secondary metabolites, including phytotoxins. Our bioassays had shown that extracts of Paraphoma sp. VIZR 1.46, a pathogen of Cirsium arvense, are phytotoxic. In this study, two phytotoxically active metabolites were isolated from Paraphoma sp. VIZR 1.46 liquid and solid cultures and identified as curvulin and phaeosphaeride A, respectively. The latter is reported also for the first time as a fungal phytotoxic product with potential herbicidal activity. Both metabolites were assayed for phytotoxic, antimicrobial and zootoxic activities. Curvulin and phaeosphaeride A were tested on weedy and agrarian plants, fungi, Gram-positive and Gram-negative bacteria, and on paramecia. Curvulin was shown to be weakly phytotoxic, while phaeosphaeride A caused severe necrotic lesions on all the tested plants. To evaluate phaeosphaeride A's herbicidal efficacy, the phytotoxic activity of this compound in combination with five different adjuvants was studied. Hasten at 0.1% (v/v) was found to be the most potent and compatible adjuvant, and its combination with 0.5% (v/v) semi-purified extract of Paraphoma sp. VIZR 1.46 solid culture exhibited maximum damage to C. arvense plants. These findings may offer significant importance for further investigation of herbicidal potential of phaeosphaeride A and possibly in devising new herbicide of natural origin.

Bio-statistical enhancement of acyl transfer activity of amidase for biotransformation of N-substituted aromatic amides.

Acyl transfer activity (ATA) of amidase transfers an acyl group of different amides to hydroxylamine to form the corresponding hydroxamic acid. Bacterial isolate BR-1 was isolated from cyanogenic plant Cirsium vulgare rhizosphere and identified as Pseudomonas putida BR-1 by 16S rDNA sequencing. This organism exhibited high ATA for the biotransformation of N-substituted aromatic amide to the corresponding hydroxamic acid. Optimization of media, tryptone (0.6%), inducer, pH 8.5, and a growth temperature 25°C for 56 h, resulted in a 7-fold increase in ATA. Further, Response Surface Methodology (RSM) and multiple feeding approach (20 mM after 14 h) of inducer led to a 29% enhancement of ATA from this organism. The half life (t1/2) of this enzyme at 50°C and 60°C was 3 h and 1 h, respectively. The ATA of amidase of Pseudomonas putida BR-1 makes it a potential candidate for the production of a variety of N-substituted aromatic hydroxamic acid.

'Candidatus Phytoplasma cirsii', a novel taxon from creeping thistle [Cirsium arvense (L.) Scop].

Creeping thistle [Cirsium arvense (L.) Scop.] and dahlia (Dahlia sp.) plants showing typical symptoms of phytoplasma infection including yellowing, stunting, inflorescence and proliferation, were sampled; the presence of phytoplasma was confirmed by standard PCR using universal primers. RFLP analysis allowed classification of the detected phytoplasma strains CirYS, CirYS1 and DahlP within the 16SrXI group, the unique restriction profile F2nR2 fragment obtained in silico by iPhyClassifier indicated that they belong to the new 16SrXI-E subgroup. Genetic analysis of the 16S rRNA gene revealed that the studied strains shared less than 97.5% similarity with all of the previously described 'Candidatus Phytoplasma' species. The closest relatives are 'Candidatus Phytoplasma cynodontis' and 'Candidatus Phytoplasma oryzae' with 96.8% and 96.6% similarity. All strains studied bear three specific regions in the 16S rRNA gene, discriminating them from the other phytoplasma species. Phylogenetic analysis of the 16S rRNA and secA genes confirmed this specificity, as the creeping thistle and dahlia phytoplasma strains clustered in a distinguishable lineage group. The uniqueness of the genetic analysis agrees with the biological characterization of the studied phytoplasma strains, their host range, and geographical distribution. The strains only infect dicotyledonous plants in Europe, contrary to their closest relatives. Based on their unique properties, it could be concluded that the studied phytoplasma strains represent a discrete group that is proposed as a novel taxon 'Candidatus Phytoplasma cirsii', with strain CirYS as a reference strain.

Rhizobacterial communities associated with spontaneous plant species in long-term arsenic contaminated soils.

The microbial community composition in three soil fractions (bulk soil, rhizosphere and rhizoplane) of the root-soil system of a thistle, Cirsium arvense, and of a tufted hair grass, Deschampsia caespitosa, was investigated. The two spontaneous wild plant species were predominant in two Italian lands contaminated since centuries by arsenic and at present show high levels of arsenic (from 215 to 12,500 mg kg(-1)). In order to better understand how the rhizobacterial ecosystem responds to a long-term arsenic contamination in term of composition and functioning, culture-independent techniques (DAPI counts, fluorescence in situ hybridization and denaturing gradient gel electrophoresis analysis) along with cultivation-based methods were applied. Microbial community structure was qualitatively similar in the two root-soil systems, but some quantitative differences were observed. Bacteria of the α-, ß-, and γ-subclasses of the Proteobacteria were dominant in all fractions, while the subdominant groups (Cytophagaceae, gram-positive spore-forming, and filamentous bacteria) were significantly more abundant in the root-soil system of D. caespitosa. As regards to arsenic resistant strains, Firmicutes, Actinobacteria, Enterobacteria and γ-Proteobacteria were isolated from soil system of both plants. Our results suggest that the response to a high level of arsenic contamination governed the rhizosphere microbial community structure together with the soil structure and the plant host type effects. Data from this study can provide better understanding of complex bacterial communities in metal-polluted soils, as well as useful information of indigenous bacterial strains with potential application to soil remediation.

Infection by a foliar endophyte elicits novel arabidopside-based plant defence reactions in its host, Cirsium arvense.

Endophytic fungi live asymptomatically within plants. They are usually regarded as nonpathogenic or even mutualistic, but whether plants respond antagonistically to their presence remains unclear, particularly in the little-studied associations between endophytes and nongraminoid herbaceous plants. We investigated the effects of the endophyte Chaetomium cochlioides on leaf chemistry in Cirsium arvense. Plants were sprayed with spores; leaf material from both subsequent new growth and the sprayed leaves was analysed 2 wk later. Infection frequency was 91% and 63% for sprayed and new growth, respectively, indicating that C. cochlioides rapidly infects new foliage. Metabolomic analyses revealed marked changes in leaf chemistry with infection, especially in new growth. Changes in several novel oxylipin metabolites were detected, including arabidopsides reported here for the first time in a plant species other than Arabidopsis thaliana, and a jasmonate-containing galactolipid. The production of these metabolites in response to endophyte presence, particularly in newly infected foliage, suggests that endophytes elicit similar chemical responses in plants to those usually produced following wounding, herbivory and pathogen invasion. Whether endophytes benefit their hosts may depend on a complex series of chemically mediated interactions between the plant, the endophyte, other microbial colonists and natural enemies.

Molecular phylogenetic status of Korean strain of Podosphaera xanthii, a causal pathogen of powdery mildew on Japanese thistle (Cirsium japonicum) in Korea.

Powdery mildew diseases are sensitive to climate change and spread can be favored by increased temperature and low moisture. During 2011 to 2012, a powdery mildew disease by a Podosphaera species was observed on the leaves of Japanese thistle (Cirsium japonicum) in Korea. The initial sign of this disease included scattered superficial white mycelia on leaves. As the disease progressed, abundant necrotic black spots exhibiting chasmothecia were formed on the leaves. rDNA ITS and 28S homologies of the fungus (EML-CSPW1) showed 100% identity values with those regions from many strains of P. xanthii (syn. P. fusca) via NCBI BLASTN search.

Differential effects of foliar endophytic fungi on insect herbivores attacking a herbaceous plant.

Foliar endophytic fungi appear to be ubiquitous in nature, occurring in a very wide range of herbaceous plants. However, their ecological role within forbs is very poorly known and interactions with foliar-feeding insects virtually unexplored. In this study, leaves of Cirsium arvense were infected with different combinations of endophyte fungi that had been previously isolated from this plant species. Two months later, leaf material was fed to larvae of a generalist insect, Mamestra brassicae, and adults of a specialist feeder, Cassida rubiginosa. Endophytes had different effects on the two insects; one species, Chaetomium cochliodes, reduced growth of M. brassicae but increased feeding by C. rubiginosa. Another species, Cladosporium cladosporioides, increased beetle feeding also, but had no effect on M. brassicae. Interactions were also seen between fungal species and dual infection with C. cladosporioides and Trichoderma viride greatly reduced beetle feeding. It is concluded that endophytes have significant effects on foliar feeding insects that differ with degree of specialism of the herbivore. We suggest that these effects are due to chemical changes in the host, brought about by fungal infection. These fungi have received remarkably little attention in the study of insect-plant interactions and yet could be important determinants of insect growth and even population dynamics.

The foliar endophytic fungal community composition in Cirsium arvense is affected by mycorrhizal colonization and soil nutrient content.

Foliar fungal endophytes are ubiquitous, but understudied symbionts of most plant species; relatively little is known about the factors affecting their occurrence, diversity and abundance. We tested the effects of soil nutrient content and arbuscular mycorrhizal (AM) colonization on the occurrence of foliar endophytic fungi in Cirsium arvense in two field studies. In the first study, we assessed relationships between soil moisture, organic matter, carbon and nitrogen content and plant water, nitrogen and carbon content and AM colonization and the occurrence of foliar endophytic fungal species. In the second study, we manipulated soil nutrient content and AM colonization of potted seedlings and identified differences in endophytic fungal species composition of the leaves and stems. The results reveal that endophytes can occur either more or less frequently, depending on soil nutrient and plant water content and AM colonization. We propose that these patterns were the result of differences in fungal growth responses to nutrient availability in the leaves, which can be affected by resources obtained from the soil or symbiotic fungi in the roots.

Arsenic-resistant bacteria associated with roots of the wild Cirsium arvense (L.) plant from an arsenic polluted soil, and screening of potential plant growth-promoting characteristics.

A rhizobacterial community, associated with the roots of wild thistle Cirsium arvense (L.) growing in an arsenic polluted soil, was studied by fluorescence in situ hybridization (FISH) analysis in conjunction with cultivation-based methods. In the bulk, rhizosphere, and rhizoplane fractions of the soil, the qualitative picture obtained by FISH analysis of the main phylogenetic bacterial groups was similar and was predominantly comprised of Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. The arsenic-resistant isolates belonged to 13 genera, the most abundant being those of Bacillus, Achromobacter, Brevundimonas, Microbacterium, and Ochrobactrum. Most bacteria grew in the presence of high arsenic concentrations (over 100mM arsenate and 10mM arsenite). Most strains possessed the ArsC, ArsB and ACR3 genes homologous to arsenate reductase and to the two classes of arsenite efflux pumps, respectively, peculiar to the ars operon of the arsenic detoxification system. ArsB and ACR3 were present simultaneously in highly resistant strains. An inconsistency between 16S rRNA phylogenetic affiliations and the arsenate reductase sequences of the strains was observed, indicating possible horizontal transfer of arsenic resistance genes in the soil bacterial community. Several isolates were able to reduce arsenate and to oxidise arsenite. In particular, Ancylobacter dichloromethanicum strain As3-1b possessed both characteristics, and arsenite oxidation occurred in the strain also under chemoautotrophic conditions. Some rhizobacteria produced siderophores, indole acetic acid and 1-amino-cyclopropane-1-carboxylic acid deaminase, thus possessing potential plant growth-promoting traits.

[Isolation, identification, and characteristics of the phytotoxin produced by the fungus Alternaria cirsinoxia].

An individual substance (20 mg/l) exhibiting phytotoxic properties, which, on the basis its spectral characteristics, was identified as zinniol, was obtained from the fungus Alternaria cirsinoxia. The nonspecific activity of this phytotoxin, with respect to plants of different families, was demonstrated. The minimum concentration (200 microg/ml) at which zinniol damages creeping thistle leaves and the median inhibition concentration (IC50) for rat embryonic fibroblasts (264 microg/ml) were determined.

Phyllostoxin and phyllostin, bioactive metabolites produced by Phyllosticta cirsii, a potential mycoherbicide for Cirsium arvense biocontrol.

Phyllosticta cirsii, a fungal pathogen isolated from diseased Cirsium arvense leaves and evaluated as a biocontrol agent of this noxious perennial weed, produces different phytotoxic metabolites with potential herbicidal activity when grown in liquid cultures. Phyllostictines A-D, four novel oxazatricycloalkenones, were recently isolated from this pathogen and chemically and biologically characterized. Further purification of the same organic extract provided two other metabolites, named phyllostoxin (1) and phyllostin (2), which were characterized by spectroscopic technique (essentially NMR and MS). Phyllostoxin and phyllostin proved to be a new pentasubstituted bicyclo-octatrienyl acetic acid ester and a new pentasubstituted hexahydrobenzodioxine carboxylic acid methyl ester, respectively. When tested on punctured C. arvense leaves, phyllostoxin proved to be highly phytotoxic, causing rapid and large necrosis, whereas phyllostin had no phytotoxicity in this bioassay. This is not surprising, considering the noteworthy structural differences between the two compounds, suggesting the presence of active functional groups in phyllostoxin not present in the other metabolite. These results further support the focused approach of finding novel metabolites with herbicidal properties by looking at the culture extracts of weed fungal pathogens.

Community structure of arbuscular mycorrhizal fungi in a primary successional volcanic desert on the southeast slope of Mount Fuji.

Community structure of arbuscular mycorrhizal fungi (AMF), evaluated as spore samples and mycorrhizal roots of four herbaceous plant species, was investigated at different altitudes in a primary successional volcanic desert on Mount Fuji using molecular methods (fragment and sequence analysis of the large ribosomal subunit RNA gene). In total, 17 different AMF clades were identified, and most were members of the Glomaceae, Acaulosporaceae, and Gigasporaceae. The AMF community structures detected by spore sampling were inconsistent with those from plant roots. Of all AMF clades, six (35.3%) were detected only on the basis of spores, six (35.3%) only in roots, and five corresponded to both spores and roots (29.4%). Although an Acaulospora species was the most dominant among spores (67.1%), it accounted for only 6.8% in root samples. A species analysis of AMF communities at different altitudes demonstrated that AMF species diversity increased as altitude decreased and that the species enrichment at lower altitudes resulted from the addition of new species rather than species replacement. The inconsistencies in the species composition of spore communities with those in roots and the change in species diversity with altitude are discussed.

Relation between in vitro production of ascosonchine and virulence of strains of the potential mycoherbicide Ascochyta sonchi: a method for its quantification in complex samples.

The potential of the fungus Ascochyta sonchi as a mycoherbicide for the biocontrol of the perennial weeds Sonchus arvensis and Cirsium arvense that occur throughout temperate regions of the world is under evaluation. Ascosonchine, a newly discovered enol tautomer of 4-pyridylpyruvic acid with potential herbicidal properties, is the main phytotoxin produced by this fungus. A simple and sensitive method has been developed for the rapid quantitative analysis of ascosonchine based on HPLC with UV detection. The toxin content in culture filtrates of different strains of A. sonchi was measured. The strains tested produced up to 2.7 mg/L when grown in static conditions. Toxin production was compared with the virulence on the host plant of each strain to determine if the most virulent strains could be simply selected by choosing the best toxin producers. The results obtained do not support this approach. The same HPLC method was also applied to quantify toxin production under different fungal growth conditions, in order to achieve the highest toxin production. The most productive strain synthesised more than 8 mg/L when grown for 8 weeks in static conditions.

Arbuscular mycorrhizal colonization of the dominant plant species in primary successional volcanic deserts on the Southeast slope of Mount Fuji.

Arbuscular mycorrhizal (AM) colonization was observed on four plant species in primary successional volcanic deserts on the Southeast slope of Mount Fuji. The AM colonization of the dominant species, Polygonum cuspidatum, contradicts the conclusion that Polygonaceae are often regarded as being non-mycorrhizal species. The secondary dominant species, Polygonum weyrichii var. alpinum, formed no mycorrhizas. The roots of Cirsium purpuratum, Clematis stans and Campanula punctata ssp. hondoensis, showed a higher percentage of AM colonization than P. cuspidatum. AM colonization and spore density in the rhizosphere soil of P. cuspidatum significantly decreased as elevation increased. AM colonization in roots of Cirsium purpuratum and Clematis stans also tended to decrease with increased altitudes. Cirsium purpuratum and Campanula punctata ssp. hondoensis formed single structural types of Arum- and Paris-type, respectively, whereas P. cuspidatum and Clematis stans formed both Arum- and Paris-type morphologies.

Arbuscular mycorrhizal status of wild plants in saline-alkaline soils of the Yellow River Delta.

A survey was made of the arbuscular mycorrhizal (AM) status of five dominant wild plants Tamarix chinensis, Phragmites communis, Suaeda glauca, Aeluropus littoralis var. sinensis and Cirsium setosum in saline-alkaline soils of the Yellow River Delta that show low plant diversity. All of the species were colonized and showed typical AM structures (arbuscules, vesicles). The colonization percentage ranged from 0.2% to 9.5%, where C. setosum was the highest. The species richness of AMF at the different sites ranged from 2.00 to 2.40 per 50 ml soil, with an average of 2.16. Species diversity ranged from 1.99 to 2.22 per 50 ml soil, with an average of 2.13. Spore density ranged from 3 to 30 per 50 ml soil, with an average of 12. Glomus was the dominant genus, with a frequency and relative abundance of 88.1% and 68.4%, respectively. G. caledonium, with a frequency and relative abundance of 15.0% and 4.6%, respectively, was the dominant species. Differences were also observed in the distribution of AMF in different soil layers. Although there were still AM fungal spores in the layer 40 cm below the surface, most spores were found at a depth of 0-40 cm.

Dynamics of a mutualism in a multi-species context.

Despite recent findings that mutualistic interactions between two species may be greatly affected by species external to the mutualism, the implications of such multi-species interactions for the population dynamics of the mutualists are virtually unexplored. In this paper, we ask how the mutualism between the shoot-base boring weevil Apion onopordi and the rust fungus Puccinia punctiformis is influenced by the dynamics of their shared host plant Cirsium arvense, and vice versa. In particular, we hypothesized that the distribution of the weevil's egg load between healthy and rust-infected thistles may regulate the abundance of the mutualists and their host plant. In contrast to our expectations we found that the dynamics of the mutualists are largely determined by the dynamics of their host. This is, to our knowledge, the first demonstration that the dynamics of a mutualism are driven by a third, non-mutualistic species.