Chestnut blight fungus in Croatia: diversity of vegetative compatibility types, mating types and genetic variability of associated Cryphonectria hypovirus 1

Abstract

In order to improve understanding of its diversity, 338 isolates of Cryphonectria parasitica , the causal agent of chestnut blight, were sampled from 10 chestnut populations throughout chestnut-growing coastal and continental areas of Croatia. Eighteen vegetative compatibility (VC) types were identified. The VC type EU-1 was the most widespread, comprising 42·9% of the isolates, followed by EU-2 (21%) and EU-12 (14·2%). In respect to the occurrence of the main VC types, the C. parasitica populations in Croatia combined features of both northwestern and southeastern European populations. Perithecia and mating-type ratios of approximately 1 : 1 were found in all populations, suggesting that sexual reproduction of the fungus is common in Croatia. Natural hypovirulence was also evident in all populations, with incidence of hypovirus-infected isolates ranging from 12·7% in Istria-Buje to 66·6% in the continental part of the country. A total of 36 hypovirus-infected isolates sampled throughout Croatia were analysed in ORF-A and ORF-B by RT-PCR/RFLP analysis. All viral isolates belonged to the Italian subtype of Cryphonectria hypovirus 1 (CHV-1) and were closely related to the isolates found in other European countries. The RFLP patterns found were also identical or similar to the patterns of three isolates collected in Croatia 22 years ago, suggesting a slow evolution of the hypovirus.

Characterization of hypovirulent isolates of the chestnut blight fungus, Cryphonectria parasitica from the Marmara and Black Sea regions of Turkey

“…In accordance with this hypothesis, the dominant vc type in Turkey (EU-1) is also frequent in many European areas (e.g. Switzerland, Italy, France, and eastern Europe) where CHV-1 subtype I occurs (Gobbin et al 2003;Carbone et al 2004;Krstin et al 2008;Robin et al 2010). Very likely, subtype I was introduced into Turkey together with its fungal host of vc type EU-1.…”

“…The Italian subtype (subtype I) is the most widespread with a distribution range spanning from France, Italy, and Switzerland to south-eastern Europe and Greece (Allemann et al 1999;Sotirovski et al 2006;Krstin et al 2008;Robin et al 2010;Krstin et al 2011). Additional CHV-1 subtypes have been found in France (subtypes F1 and F2) and in Spain and Germany (subtype E/D) (Gobbin et al 2003;Montenegro et al 2008).…”

Diversity and spatial distribution of vegetative compatibility types and mating types of Cryphonectria parasitica in the Aydın Mountains, Turkey

“…In the Black Sea Region, two recently reported vc types (EU-2 and EU-14; Akıllı et al 2009) are known to be two of 14 vc types, which could have been generated from the EU-1 and EU-12 cross (Cortesi and Milgroom 1998). High vc-type diversity of C. parasitica was observed in some European countries such as France, Italy, Switzerland, Bosnia-Herzegovina (Robin and Heiniger 2001) and Croatia (Krstin et al 2008), where C. parasitica is known to reproduce sexually. On the other hand, certain Balkan countries such as Macedonia (Sotirovski et al 2004) and Greece (Perlerou and Diamandis 2006), where C. parasitica did not have sexual stage, were reported to have lower vc-type diversity.…”

Cryphonectria parasitica isolates of the same vegetative compatibility type display different rates of transfer of CHV1 hypovirus

“…Natural biological control of the chestnut blight fungus, using the Italian subtype of hypovirus CHV1, has been successful in different European countries (Heiniger and Rigling 1994;Sotirovski et al 2006;Krstin et al 2008;Robin et al 2010). Within Spain, CHV1 subtype I has been successful in controlling chestnut blight and has been widely dispersed in Cataluña (Colinas et al 2009).…”

“…Since then several subtypes have been identified (Allemann et al 1999;Gobbin et al 2003). The Italian subtype (subtype I) is the most widespread (Italy, Switzerland, France, Hungary, Croatia, Bosnia and Herzegovina, Macedonia, Turkey, Greece and Spain) (Allemann et al 1999;Sotirovski et al 2006;Krstin et al 2008;Robin et al 2010;Krstin et al 2011;Akilli et al 2013;Castaño et al 2015). Other subtypes of CHV1 are found in Germany (subtype D), France (Subtypes F1 and F2) and Spain (Subtypes F1 and E) (Allemann et al 1999;Gobbin et al 2003;Zamora et al 2012).…”