A New Double-Stranded RNA Mycovirus in Cryphonectria naterciae Is Able to Cross the Species Barrier and Is Deleterious to a New Host

Abstract

Cryphonectria is a fungal genus associated with economically significant disease of trees. Herein we characterized a novel double-stranded RNA virus from the fungal species Cryphonectria naterciae, a species unexplored as a virus host. De novo assembly of RNA-seq data and Sanger sequencing of RACE (rapid amplification of cDNA ends) clones gave the complete, non-segmented genome (10,164 bp) of the virus termed Cryphonectria naterciae fusagravirus (CnFGV1) that was phylogenetically placed within the previously proposed viral family Fusagraviridae. Of 31 field-collected strains of C. naterciae, 40% tested CnFGV1-positive. Cocultivation resulted in within-species transmission of CnFGV1 to virus-free strains of C. naterciae. Comparison of the mycelium phenotype and the growth rate of CnFGV1-infected and virus-free isogenic strains revealed frequent sectoring and growth reduction in C. naterciae upon virus infection. Co-culturing also led to cross-species transmission of CnFGV1 to Cryphonectria carpinicola and Cryphonectria radicalis, but not to Cryphonectria parasitica. The virus-infected C. naterciae and the experimentally infected Cryphonectria spp. readily transmitted CnFGV1 through asexual spores to the next generation. CnFGV1 strongly reduced conidiation and in some cases vegetative growth of C. carpinicola, which is involved in the European hornbeam disease. This study is the first report of a fusagravirus in the family Cryphonectriaceae and lays the groundwork for assessing a hypovirulence effect of CnFGV1 against the hornbeam decline in Europe.

A new tetra-segmented splipalmivirus with divided RdRP domains from Cryphonectria naterciae, a fungus found on chestnut and cork oak trees in Europe

“…C. naterciae has not yet been extensively explored as a virus host. We searched a collection of Portuguese isolates of C. naterciae for mycoviruses several years ago and characterized omnipresent viruses as well as peculiar viruses such as fusagraviruses (unclassified dsRNA viruses) (Cornejo et al, 2021b).…”

New detections of chestnut blight in Great Britain during 2019–2020 reveal high Cryphonectria parasitica diversity and limited spread of the disease

“…The discovery of CHV‐1 in C . radicalis represents, to the best of our knowledge, the first detections of CHV‐1 in this species in the wider environment (Chen et al, 1994; Cornejo et al, 2021). However, its presence could be an indicator of how long chestnut blight has been present in the United Kingdom because natural hypovirulence starts to appear and reduces the severity of chestnut blight outbreaks in Europe one to three decades after the establishment of a new chestnut blight fungus population (Milgroom & Cortesi, 2004).…”

Multiplex Detection of Pleurotus ostreatus Mycoviruses

“…To the best of our knowledge, this study is the first to report multiplex RT-PCR detection of P. ostreatus mycoviruses. Previous reports have demonstrated that some mycoviruses such as Cryphonectria hypovirus 1 (CHV1), Cryphonectria naterciae fusagravirus 1 (CnFGV1), and Cryphonectria nitschkei chrysovirus 1 (CnCV1) can cross the barrier of incompatibility and infect different related species of fungi [ 42 , 43 , 44 ]. To date, it is not clear whether the four known P. ostreatus mycoviruses (OMSV, OMIV, POSV, and PoV1) could infect other closely-related host species.…”