Fusarium circinatum Nirenberg & O’Donnell (teleomorph = Gibberella circinata) is an ascomycete fungus and the causal agent of Pine Pitch Canker (PPC), a disease that causes substantial damages and loss in pine forests and plantations and is considered the most detrimental pathogen of Pinus seedlings in several countries around the world. PPC disease arrived to Europe in the year 2004, when Spain discovered the presence of the pathogen in pine nurseries in Asturias and on plantations in Cantabria. Since then, various scientific studies have evaluated the genetic diversity of the pathogen’s populations, its pathogenicity, and the role some insect species play as possible vectors in the spread of the disease.Recently, this research group has detected the presence of different viral RNA molecules in some isolates of the Spanish F. circinatum population, finding three viral strains belonging to two new different species of the genus Mitovirus, Fusarium circinatum mitovirus 1 (FcMV1), FcMV2-1 and FcMV2-2. The viruses found were common in the Spanish population of the pathogen, with almost 32% of the isolates infected by at least one of the three viral strains. These RNA molecules could have the potential to trigger hypovirulent processes in the fungal host, similar to what happens with Cryphonectria parasitica, the causal agent of the chestnut blight, which is effectively controlled by this method in the forest. However, in the first inoculation trials this effect was discarded, making the search for new mycoviruses imperative.
The virus detection techniques routinely used, like reverse transcription-polymerase chain reaction (RT-PCR), require prior knowledge of the virus in order for it to be detected and are, thus, inadequate for the detection of mycoviruses in fungus, of which very little is known to date. A metagenomic approach, coupled with Next Generation Sequencing (NGS), however, has the power to determine the complete virus community or virome of an organism, including mycoviruses.
The main objective of the present project is to use the NGS to: (1) identify the viral molecules hosted in isolates of F. circinatum from all around the world; (2) study the effect of the mycoviruses on Fusarium circinatum; and (3) study the effect of mycoviruses-free F. circinatum and mycoviruses-infected F. circinatum on inoculated pine seedlings. The achievement of these aims will clarify if there is any possibility that this strategy could aid in the control of pitch canker disease in Spain.