Ioly Kotta-Loizou, University of Hertfordshire

John O. Daudu (1), James Snowden (2), Josephine L. Battersby (1,3), Unnati A. Shah (1), Charalampos Filippou (1) , Pedro Romon-Ochoa (2), Katherine V. Tubby (2), Robert H. A. Coutts (1), Ioly Kotta-Loizou (1,3)* (1) School of Health, Medicine and Life Sciences, University of Hertfordshire, Hatfield, AL10 9AB, UK (2) Forest Research, Alice Holt Lodge, Wrecclesham, Farnham, GU10 4LH, UK (3) Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK *Email: i.kotta-loizou2@herts.ac.uk; i.kotta-loizou13@imperial.ac.uk

Epidemiology, Evolution, and Diversity

Red-band needle blight, also known as pine needle blight or Dothistroma needle blight, is an economically important disease of conifers, particularly pine trees. It is caused by the phytopathogenic fungus Dothistroma septosporum, which has a worldwide distribution and is a relatively strict pathogen, therefore grows very slowly in artificial medium. The aim of the study was to investigate the diversity of mycoviruses in D. septosporum, together with their role in fungal pathogenesis. To this end, British and Turkish D. septosporum field isolates were screened for the presence and quantity of 14 mycoviruses. A novel mycovirus named Dothistroma septosporum chrysovirus (DsCV) 1, belonging to genus Alphachrysovirus, family Chrysoviridae, was initially identified using a small-scale double-stranded (ds) RNA extraction protocol and represents the first mycovirus discovered in D. septosporum. DsCV1 was detected in D. septosporum populations from the UK (England, Wales and Scotland) and Turkey using reverse transcription followed by quantitative polymerase chain reaction (RT-qPCR). Subsequently, a DsCV-1-infected D. septosporum isolate from Scotland was selected for further investigation. Following treatment with the nucleoside analogue ribavirin and DsCV1 eradication, the growth and virulence of virus-infected and virus-free isogenic lines were compared in vitro and in planta. DsCV1 infection reduced host growth and resulted in hypovirulence on pine saplings when fungal virulence was assessed by visual inspection, image analysis and qPCR. These results illustrate the potential of DsCV1 for biological control of red-band needle blight in affected pine trees, similar to Cryphonectria hypovirus 1 against the chestnut blight fungus Cryphonectria parasitica.