Temperature Effects on the Cryphonectria hypovirus 1 Accumulation and Recovery within Its Fungal Host, the Chestnut Blight Pathogen Cryphonectria parasitica

Abstract

Biological control of Cryphonectria parasitica fungus, the causal agent of chestnut blight, by virus infection (hypovirulence) is an effective control strategy against chestnut blight in Europe and some parts of North America. The most studied mycovirus is the Cryphonectria hypovirus 1 (CHV1) type species of the Hypoviridae family. In this study, the CHV1 virus was studied within some highly infected British isolates of Cryphonectria parasitica, gained in the past through co-culture transmissions. The effects of six temperatures (5–30 °C, in 5 °C steps) on six infected isolates (three with viral strain E-5, and other three with viral strain L-18) and their respective negative non-infected controls, three isogenic virulent fungal isolates, were examined. Experiments were performed with the nine isolate types with three replicates on potato dextrose agar (PDA) with cellophane sheets per isolate and temperature. A recently developed rapid, specific, quantitative reverse transcription PCR (RT-qPCR) screening method was used. This enabled quantifying the concentration (nanograms per microliter or copy numbers) of the virus within each isolate repetition. The presence of the virus had a significant negative effect between 20 and 25 °C on the C. parasitica growth rate, which was anyway highly influenced by and positively correlated with the temperature. The temperature clearly determined the virus accumulation and its recovery from cold or heat, and the virus optimum temperature was estimated at 15–25 °C.

Cryphonectria parasitica Detections in England, Jersey, and Guernsey during 2020–2023 Reveal Newly Affected Areas and Infections by the CHV1 Mycovirus

“…Contrary to North America, where the CHV1 spread is highly hampered by the high number of VCGs, research in England is now mainly focused on possible biocontrol using CHV1 on sites where one dominant VCG is present and where CHV1 has been detected, such as London (EU10), Devon (EU9), and Nottinghamshire (EU9). CHV1 from highly infected fungal strains from continental Europe (mainly EU10 and EU9) has been successfully transmitted to uninfected English C. parasitica isolates of the same VCGs, and further experiments about the in planta behaviour under controlled conditions of these virus-infected isolates have been completed successfully [27,42,43]. This success, along with the evidence of three findings of naturally occurring CHV1 observed in this study, is encouraging, and paves the way for further research into its use as a biocontrol agent in the UK, subject to the relevant field permits and regulatory consent, given that this fungal pathogen is considered a protected-zone quarantine pest in the European Union according to the Commission Implementing Regulation 2019/2072.…”

Forecasting of Airborne Conidia Quantities and Potential Insect Associations of Cryphonectria parasitica, the Causal Agent of Chestnut Blight, in England

“…Research is now focused on possible biocontrol using Cryphonectria hypovirus 1 (CHV1) on those sites where one dominant Vegetative Compatibility Group (VCG) [ 12 ] is present, and CHV1 has been detected. CHV1 from highly infected fungal strains from Europe has been successfully transmitted to uninfected English C. parasitica isolates of the same VCGs (mainly EU10 and EU9) and further experiments about the in planta and thermal behaviour, under controlled conditions, of those virus-infected isolates have been completed successfully [ 13 , 14 ].…”