Diversity and ecology of Armillaria species in virgin forests in the Ukrainian Carpathians

In this study, we investigated the diversity and ecology of Armillaria species in virgin pure beech and mixed conifer forests (15,000ha) of the Carpathian Biosphere Reserve in Ukraine. Armillaria rhizomorphs were systematically sampled, both from the soil and from the root collar of trees (epiphytic), on 79 plots (25 × 20m) of a 1.5 × 1.5km grid. In both forest massifs, rhizomorphs were present in the majority of the soil samples, with an estimated dry weight of 512kg/ha in the pure beech forests and 223kg/ha in the mixed conifer forests. Similarly, in both forest massifs, most of the trees inspected had rhizomorphs at the root collar. Species identification based on DNA analyses showed that all five annulated European Armillaria species occur in these virgin forests, as previously observed in managed forests in central Europe. However, differences in the frequencies of the single species were observed. The predominance of the preferentially saprotrophic A. cepistipes and A. gallica (84 and 15% of the specimens, respectively) and the absence of significant pathogenic activity suggest that in these virgin forests Armillaria species are most likely to behave as saprotrophs. Forest management may increase the frequency of the pathogenic species A. ostoyae, which is rare in virgin forest

Eight microsatellite markers for Armillaria cepistipes and their transferability to other Armillaria species

We isolated eight polymorphic microsatellite markers for the basidiomycete Armillaria cepistipes and characterised them by analysing 50 isolates representing two geographically distinct populations from Switzerland and the Ukraine. The number of alleles per locus and population varied from one to eight, resulting in 43 alleles over the eight loci and two populations. In both populations, no significant linkage disequilibrium was observed between pairs of loci. Significant (P < 0.05) deviations from Hardy-Weinberg equilibrium were observed at one locus in the Swiss population and at three loci in the Ukrainian population. Of the eight loci developed for A. cepistipes, six were also polymorphic in A. gallica, four in A. ostoyae, two in A. mellea, and one in A. borealis. Beside the potential to be used for population genetic studies on A. cepistipes, these microsatellites thus represent additional molecular markers for three of the four annulated Armillaria species occurring in Europ

Interaction between two invasive organisms on the European chestnut: does the chestnut blight fungus benefit from the presence of the gall wasp?

The impact of invasive fungal pathogens and pests on trees is often studied individually, thereby omitting possible interactions. In this study the ecological interaction between the chestnut blight fungus Cryphonectria parasitica and the chestnut gall wasp Dryocosmus kuriphilus was investigated. We determined if abandoned galls could be colonized by C. parasitica and thereby act as an entry point and a source of pathogen inoculum. Moreover we assessed the identity and diversity of other gall-colonizing fungal species. A total of 1973 galls were randomly sampled from 200 chestnut trees in eight Swiss stands. In a stand C. parasitica was isolated from 0.4-19.2% of the galls. The incidence of C. parasitica on the galls and the fungal diversity significantly increased with the residence time of D. kuriphilus in a stand. All but one C. parasitica cultures were virulent. The predominant fungus isolated from galls was Gnomoniopsis castanea whose abundance influenced negatively that of C. parasitica. This study shows that D. kuriphilus galls can be colonized by virulent strains of the chestnut blight fungus C. parasitica. This can have effects on the chestnut blight incidence even in chestnut stands where the disease is successfully controlled by hypovirulence. The gall wasp presence influences also the fungal species composition on chestnut tree

Biological control of chestnut blight. Detection, identification and characterization of the Hypovirus - CHV1

O cancro do castanheiro é provocado pelo fungo Cryphonectria parasitica é considerado a principal causa do declínio dos castanheiros na Europa. C. parasitica é um ascomiceta (Diaporthales) nativo do continente asiático. A infeção do castanheiro manifesta-se pelo aparecimento de necroses extensas na casca dos ramos e troncos, que resulta na morte dos castanheiros. A hipovirulência é um método seletivo de controlo biológico do Cancro do Castanheiro, trata-se de uma infeção do fungo C. parasitica com Cryphonectria hypovirus 1 (CHV1), um vírus de dsRNA não encapsulado do género Hypovirus. O controlo biológico com estirpes hipovirulentas é considerado um método eficaz no controlo da doença e promove a recuperação dos castanheiros. A aplicação necessita da produção em laboratório de estirpes hipovirulentas compatíveis com a estirpe virulenta presente no campo e a sua introdução na margem de cancros ativos. Neste estudo pretendeu-se detetar, identificar e caracterizar o hipovirus CHV1 com potencial para integrar programas de controlo biológico do Cancro do castanheiro em Portugal. Com a utilização de métodos moleculares foram identificados e caracterizados 11 hipovirus em isolados brancos de C. parasitica obtidos em cancros no nordeste de Portugal.The chestnut blight caused by the fungus Cryphonectria parasitica is considered a major cause of the decline and disappearance of chestnut trees across Europe. C. parasitica is an ascomycete fungus (Diaporthales) that is native to eastern Asia. Infection of chestnut plants with this fungus is typically associated with extensive necrosis (cankers) of the bark on stems and branches, resulting in the subsequent death of the tree. Hypovirulence is a specific method for biological control of Chestnut Blight, it is an infection of C. parasitica with Cryphonectria hypovirus 1 (CHV1), a unencapsidate dsRNA virus of the genus Hypovirus. Biological control with hypovirulent strains is considered an efficient method to control the disease and improve the host plant recovery. The field application needs laboratorial production of compatible hypovirulent strain and introduction by inoculation at the margin of active cankers. In this work it was intended to identify and characterize the hypovirus with potential ability to integrate biological control programmes against Chestnut Blight. Using molecular techniques 11 hypovirus with hypovirulence potential were identified on white isolates of C. parasitica isolated on cankers from northeast of Portugal

Genetic diversity of the Chestnut blight fungus Cryphonectria parasitica and its associated hypovirus in Portugal

The European chestnut (Castanea sativa Mill.) agro‐ecosystem has been of high social, economic, and landscape importance in Portugal. Chestnut blight caused by the fungus Cryphonectria parasitica is considered a major cause of the decline of chestnut trees across Europe. C. parasitica is an ascomycete (Diaporthales) that is native to eastern Asia. Infection of chestnut trees with this pathogen is typically associated with extensive bark necrosis (so‐called cankers) on stems and branches, resulting in the subsequent death of the part of the tree above the infection point. Chestnut blight in Portugal was first reported in 1992 and since expanding in distribution. Here, we investigated the invasion history of C. parasitica and its associated hypovirus in Portugal. For this, we characterized 137 isolates collected between 2013 and 2014 in four chestnut stands for virus‐infection, vegetative compatibility (vc) type, mating type and microsatellite haplotype. A total of 33 haplotypes and four vc types were observed, although the Portuguese C. parasitica population is currently dominated by a single haplotype and a single vc type (EU‐11). Further diversification may be expected due to ongoing sexual recombination, but eventually also to new migration and additional introductions. Cryphonectria hypovirus 1 (CHV‐1) was found in two populations. Genetic analysis of the six CHV‐1 isolates obtained revealed that three viral strains belong to the Italian subtype and three to the French subtype, which suggest different, independent introductions.info:eu-repo/semantics/publishedVersio

Eficácia do tratamento do Cancro do Castanheiro em ensaios de inoculação com estirpes hipovirulentas de Cryphonectriaparasitica(CHV1) em Trás-os-Montes (Portugal)

O castanheiro europeu (Castanea sativa Mill) é a principal espécie do sistema agroflorestal nas regiões montanhosas de Portugal. O castanheiro é atualmente afetado por vários agentes patogénicos agressivos, destacando-se o fungo Cryphonectria parasitica, que causa o Cancro do Castanheiro, que provoca a morte da árvore. A Hipovirulência, associada à presença de Cryphonectria hypovirus 1 no fungo fitoparasita, é um método específico e eficiente no controlo biológico do Cancro do Castanheiro. Para uma aplicação eficaz deste método no campo é necessário conhecer as características das estirpes agressivas de C. parasitica presentes no campo. Na Serra da Padrela foi selecionado um souto para realizar este estudo. Foi efetuado uma caracterização dos cancros ativos, e posteriormente o seu tratamento por Hipovirulência. Dos isolados obtidos dos cancros, 99% eram agressivos, sendo identificados 3 isolados como hipovirulentos. Todos foram classificados como vc-type EU-11, estando em maior abundância o mating-type 2, numa proporção de 2:1 comparativamente ao mating-type 1. Os cancros agressivos foram tratados com as estirpes hipovirulentas compatíveis tendo-se observado ao fim de 1 ano uma recuperação das árvores afetadas tendo-se confirmado a presença das estirpes hipovirulentas em cancro anteriormente agressivos

Caracterização da estrutura populacional de Cryphonectria parasitica para aplicação da luta biológica por hipovirulência: um caso de estudo na Serra da Padrela

O castanheiro europeu (Castanea sativa Mill) é a principal espécie do sistema agroflorestal nas regiões montanhosas de Portugal. O castanheiro é atualmente afetado por vários agentes patogénicos agressivos, destacando-se o fungo Cryphonectria parasitica, que causa o Cancro do Castanheiro, que provoca a morte da árvore. A Hipovirulência, associada à presença de Cryphonectria hypovirus 1 no fungo fitoparasita, é um método específico e eficiente no controlo biológico do Cancro do Castanheiro. Para uma aplicação eficaz deste método no campo é necessário conhecer as características das estirpes agressivas de C. parasitica presentes no campo. Na Serra da Padrela foi selecionado um souto para realizar este estudo. Foi efetuado uma caracterização dos cancros ativos, e posteriormente o seu tratamento por Hipovirulência. Dos isolados obtidos dos cancros, 99% eram agressivos, sendo identificados 3 isolados como hipovirulentos. Todos foram classificados como vc-type EU-11, estando em maior abundância o mating-type 2, numa proporção de 2:1 comparativamente ao mating-type 1. Os cancros agressivos foram tratados com as estirpes hipovirulentas compatíveis tendo-se observado ao fim de 1 ano uma recuperação das árvores afetadas tendo-se confirmado a presença das estirpes hipovirulentas em cancro anteriormente agressivos

Worldwide diversity of endophytic fungi and insects associated with dormant tree twigs

International trade in plants and climate change are two of the main factors causing damaging tree pests (i.e. fungi and insects) to spread into new areas. To mitigate these risks, a large-scale assessment of tree-associated fungi and insects is needed. We present records of endophytic fungi and insects in twigs of 17 angiosperm and gymnosperm genera, from 51 locations in 32 countries worldwide. Endophytic fungi were characterized by highthroughput sequencing of 352 samples from 145 tree species in 28 countries. Insects were reared from 227 samples of 109 tree species in 18 countries and sorted into taxonomic orders and feeding guilds. Herbivorous insects were grouped into morphospecies and were identified using molecular and morphological approaches. This dataset reveals the diversity of tree-associated taxa, as it contains 12,721 fungal Amplicon Sequence Variants and 208 herbivorous insect morphospecies, sampled across broad geographic and climatic gradients and for many tree species. This dataset will facilitate applied and fundamental studies on the distribution of fungal endophytes and insects in trees.Estación Experimental Agropecuaria BarilocheFil: Franic, Iva. CABI; SuizaFil: Franic, Iva. Instituto Federal Suizo para la Investigación de Bosques, Nieve y Paisajes; SuizaFil: Prospero, Simone. Instituto Federal Suizo para la Investigación de Bosques, Nieve y Paisajes; SuizaFil: Adamson, Kalev. Estonian University of Life Sciences. Institute of Forestry and Rural Engineering; EstoniaFil: Corley, Juan Carlos. Instituto Nacional de Tecnologia Agropecuaria (INTA). Estacion Experimental Agropecuaria Bariloche; ArgentinaFil: Corley, Juan Carlos. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Lantschner, Maria Victoria. Instituto Nacional de Tecnologia Agropecuaria (INTA). Estacion Experimental Agropecuaria Bariloche. Area Forestal; ArgentinaFil: Lantschner, Maria Victoria. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Soliani, Carolina. Instituto Nacional de Tecnologia Agropecuaria (INTA). Estacion Experimental Agropecuaria Bariloche. Area Forestal; ArgentinaFil: Soliani, Carolina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Eschen, René. CABI; Suiz

Global invasion history of the emerging plant pathogen Phytophthora multivora

BACKGROUND: global trade in living plants and plant material has significantly increased the geographic distribution of many plant pathogens. As a consequence, several pathogens have been first found and described in their introduced range where they may cause severe damage on naïve host species. Knowing the center of origin and the pathways of spread of a pathogen is of importance for several reasons, including identifying natural enemies and reducing further spread. Several Phytophthora species are well-known invasive pathogens of natural ecosystems, including Phytophthora multivora. Following the description of P. multivora from dying native vegetation in Australia in 2009, the species was subsequently found to be common in South Africa where it does not cause any remarkable disease. There are now reports of P. multivora from many other countries worldwide, but not as a commonly encountered species in natural environments. RESULTS: a global collection of 335 isolates from North America, Europe, Africa, Australia, the Canary Islands, and New Zealand was used to unravel the worldwide invasion history of P. multivora, using 10 microsatellite markers for all isolates and sequence data from five loci from 94 representative isolates. Our population genetic analysis revealed an extremely low heterozygosity, significant non-random association of loci and substantial genotypic diversity suggesting the spread of P. multivora readily by both asexual and sexual propagules. The P. multivora populations in South Africa, Australia, and New Zealand show the most complex genetic structure, are well established and evolutionary older than those in Europe, North America and the Canary Islands. CONCLUSION: according to the conducted analyses, the world invasion of P. multivora most likely commenced from South Africa, which can be considered the center of origin of the species. The pathogen was then introduced to Australia, which acted as bridgehead population for Europe and North America. Our study highlights a complex global invasion pattern of P. multivora, including both direct introductions from the native population and secondary spread/introductions from bridgehead populations.http://www.biomedcentral.com/bmcgenomicsForestry and Agricultural Biotechnology Institute (FABI

Population History and Pathways of Spread of the Plant Pathogen Phytophthora plurivora

Human activity has been shown to considerably affect the spread of dangerous pests and pathogens worldwide. Therefore, strict regulations of international trade exist for particularly harmful pathogenic organisms. Phytophthora plurivora, which is not subject to regulations, is a plant pathogen frequently found on a broad range of host species, both in natural and artificial environments. It is supposed to be native to Europe while resident populations are also present in the US. We characterized a hierarchical sample of isolates from Europe and the US and conducted coalescent-, migration, and population genetic analysis of sequence and microsatellite data, to determine the pathways of spread and the demographic history of this pathogen. We found P. plurivora populations to be moderately diverse but not geographically structured. High levels of gene flow were observed within Europe and unidirectional from Europe to the US. Coalescent analyses revealed a signal of a recent expansion of the global P. plurivora population. Our study shows that P. plurivora has most likely been spread around the world by nursery trade of diseased plant material. In particular, P. plurivora was introduced into the US from Europe. International trade has allowed the pathogen to colonize new environments and/or hosts, resulting in population growth