Identification and characterization of hypovirus-infected Cryphonectriaparasiticaisolates from biological control plots in İzmir, Kütahya, and Sinop

Seçil Akilli Şi̇mşe,Deniz Çakar,Nora Borst,Y Zekai Katircioğlu,Salih Maden,Daniel Rigling,Simone Prospero

doi:10.3906/tar-1901-82

Abstract

In a pilot study, a biological control with hypovirus-infected Cryphonectria parasitica was applied in 3 study plots in Turkey, in June 2013. The aim of this study was to evaluate the success of the applied biological control by verifying the establishment of the released hypovirus (CHV-1) strains using molecular markers. C. parasitica isolates were sampled from cankers at 3 different time points: before the biological control treatments (April 2013), and 5 months (October 2013) and 11 months (May 2014) after the treatment. In total, 255 C. parasitica isolates were recovered and characterized. First, the culture morphology and vegetative compatibility type of these isolates were assessed. Next, the presence of hypoviruses in white isolates was checked by RNA extraction and subsequent RTPCR. Finally, a sequence analysis was performed to compare the hypoviruses to the released biological control hypoviruses by examining single nucleotide markers and reconstructing their phylogenetic relationship. The study sites in İzmir and Kütahya were found to be free of hypoviruses prior to the biological control, whereas in Sinop, the occurrence of hypoviruses of the Italian subtype was observed. Reisolations of the treated cankers and subsequent molecular analysis resulted in the detection of the released biocontrol hypovirus strains in all 3 study sites. The reisolated hypoviruses in İzmir and Kütahya originated from either one of the released biocontrol strains. In Sinop, both natural and artificially introduced hypoviruses were detected. Our study showed that the released biological control hypoviruses persisted in the treated cankers, which is promising for the biological control of chestnut blight in Turkey.

Highlights

In Turkey, sweet chestnut, Castanea sativa Mill., with an acreage of about 262,000 ha, as in pure stands (11.3%), stands mixed with deciduous trees (73.4%), and in stands mixed with conifers (9.3%), is an important tree species with horticultural benefits
Original populations In order to determine the occurrence of the vc types and CHV-1 at the 3 study sites (İzmir, Kütahya, and Sinop), the ORIG C. parasitica populations were characterized prior to the biological control with hypovirulence
This phenomenon is caused by a hyperparasitic hypovirus (CHV-1) that infects C. parasitica, thereby acting as a biological control agent against chestnut blight

Summary

Introduction

In Turkey, sweet chestnut, Castanea sativa Mill., with an acreage of about 262,000 ha, as in pure stands (11.3%), stands mixed with deciduous trees (73.4%), and in stands mixed with conifers (9.3%), is an important tree species with horticultural benefits. After a great expansion and damage, the infected trees began to recover from the disease in many stands in Europe, as indicated by the occurrence of superficial nonlethal bark cankers. This recovery has been attributed to hypovirulence, a phenomenon in which fungal viruses infect C. parasitica and significantly reduce its virulence and sporulation capacity (Grente, 1965; Choi and Nuss, 1992; Heiniger and Rigling, 1994; Milgroom and Cortesi, 2004)

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