Distribution and population structure of the chestnut blight fungus in Romania

Bolea

et al. 2017

Not Bot Horti Agrobo

Asiatic fungus Cryphonectria parasitica has gradually infected all chestnut habitats, forest and horticulture plantations from the most important natural centres of sweet chestnut distribution in Romania. The objectives of this work were to understand the destruction rate of chestnut habitats under C. parasitica pressure, and to test the efficacy of pathogen control in revitalizing these protected forests. Successive inventories of forest health status were carried out in forest districts of Maramures and Gorj counties. C. parasitica biologic control using CHV1 virus has been tested. The methodology includes standard laboratory and field work techniques: local hipervirulent strain identification and conversion to hipovirulence, field canker inoculation, and treatment efficacy evaluation. The fungus killed all mature chestnut trees in roughly two decades. Field inoculation has been successful on chestnut and sessile oak (fungus secondary host) in experimental plots from both target zones. This is the first time in Romania when a forest habitat is recovered by means of biological control, after a severe dieback of the old forest caused by a lethal invasive pathogen.

“…Similar results have been recorded in the same zones, both on chestnut and sessile oak (Radocz, 2001;Tarcali, 2007;Adamčíková et al 2015;Görcsös et al, 2015).…”

Section: Healing Evolutionsupporting

confidence: 83%

Biological Control of Cryphonectria parasitica in Romanian Protected Sweet Chestnut Forests

Bolea

et al. 2017

Not Bot Horti Agrobo

“…In the eastern European countries close to western Turkey, EU‐12 was highly dominant. According to previous reports, 80.5% of Bulgarian isolates (Risteski et al., ), 96% of Macedonian isolates (Sotirovski et al., ), 88% of Greek isolates (Perlerou & Diamandis, ) and 99% of Romanian isolates (Adamčíková et al., ) were identified as EU‐12. This vc type was likely introduced to the Aegean region from one of these countries.…”

Section: Discussionmentioning

confidence: 95%

Geographical distribution of vegetative compatibility and mating types of Cryphonectria parasitica in İzmir, Manisa and Denizli provinces in western Turkey

2018

To extend our knowledge of population structure of Cryphonectria parasitica in the Aegean region, 264 isolates obtained from eight subpopulations in Izmir, Manisa and Denizli provinces were studied. Only three vegetative compatibility (vc) types, EU‐1, EU‐12 and EU‐2, were identified. EU‐1 (59%) was dominant and was found in all eight subpopulations. EU‐12 (32%) was detected in six subpopulations and was highly dominant (71%) in the Ödemiş subpopulation (İzmir province). EU‐2 was restricted to only one subpopulation, Tire, but, there, had the highest frequency (50%). This is the first reported occurrence of EU‐2 in western Turkey. Regarding sexual compatibility, both MAT1‐1 and MAT1‐2 were detected in all subpopulations; however, 85% of the isolates were MAT1‐1 and no perithecia were found in any of the subpopulations. Multilocus linkage disequilibrium analysis determined that all subpopulations were clonal. Indicator co‐kriging representations showed that vc types and mating types were spatially aggregated. In combination, these results indicate that the dispersal of the pathogen most likely occurs via localized short‐distance transport of rain‐splashed asexual conidia, rather than the long‐distance dispersal of wind‐borne ascospores. Because of the presence four polymorphic vegetative incompatibility (vic) loci in certain subpopulations, C. parasitica has the potential to generate new vc types in the future.

Molecular Plant Pathology

“…It should be noted that there are still areas in which chestnut blight is present but CHV‐1 has not been detected or its prevalence is very low. Such areas include Portugal (Bragança et al ., ), Spain (Castano et al ., ; Zamora et al ., ), Bulgaria (Risteski et al ., ), Romania (Adamcikova et al ., ), northern Switzerland (Hoegger et al ., ) and the Aegean region of Turkey (Erincik et al ., ).…”

Section: Biological Control Using Hypovirulencementioning

confidence: 99%

Cryphonectria parasitica, the causal agent of chestnut blight: invasion history, population biology and disease control

Rigling

Prospero

2017

369

295

Summary Chestnut blight, caused by Cryphonectria parasitica, is a devastating disease infecting American and European chestnut trees. The pathogen is native to East Asia and was spread to other continents via infected chestnut plants. This review summarizes the current state of research on this pathogen with a special emphasis on its interaction with a hyperparasitic mycovirus that acts as a biological control agent of chestnut blight. Taxonomy Cryphonectria parasitica (Murr.) Barr. is a Sordariomycete (ascomycete) fungus in the family Cryphonectriaceae (Order Diaporthales). Closely related species that can also be found on chestnut include Cryphonectria radicalis, Cryphonectria naterciae and Cryphonectria japonica. Host range Major hosts are species in the genus Castanea (Family Fagaceae), particularly the American chestnut (C. dentata), the European chestnut (C. sativa), the Chinese chestnut (C. mollissima) and the Japanese chestnut (C. crenata). Minor incidental hosts include oaks (Quercus spp.), maples (Acer spp.), European hornbeam (Carpinus betulus) and American chinkapin (Castanea pumila). Disease symptoms Cryphonectria parasitica causes perennial necrotic lesions (so‐called cankers) on the bark of stems and branches of susceptible host trees, eventually leading to wilting of the plant part distal to the infection. Chestnut blight cankers are characterized by the presence of mycelial fans and fruiting bodies of the pathogen. Below the canker the tree may react by producing epicormic shoots. Non‐lethal, superficial or callusing cankers on susceptible host trees are usually associated with mycovirus‐induced hypovirulence. Disease control After the introduction of C. parasitica into a new area, eradication efforts by cutting and burning the infected plants/trees have mostly failed. In Europe, the mycovirus Cryphonectria hypovirus 1 (CHV‐1) acts as a successful biological control agent of chestnut blight by causing so‐called hypovirulence. CHV‐1 infects C. parasitica and reduces its parasitic growth and sporulation capacity. Individual cankers can be therapeutically treated with hypovirus‐infected C. parasitica strains. The hypovirus may subsequently spread to untreated cankers and become established in the C. parasitica population. Hypovirulence is present in many chestnut‐growing regions of Europe, either resulting naturally or after biological control treatments. In North America, disease management of chestnut blight is mainly focused on breeding with the goal to backcross the Chinese chestnut's blight resistance into the American chestnut genome.