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Summary. Pinus radiata is a tree species native to the Central Coast of California and Mexico, which has been widely introduced in Europe for wood production. In Spain, especially in the northern region, it was introduced in the nineteenth century. Plantations located in the Basque Country (northern Spain) showing symptoms of Diplodia shoot blight were studied to confirm the causative pathogen species. Symptomatic and asymptomatic trees were sampled, and more than 150 fungal isolates obtained were morphologically characterized, with identities confirmed by sequencing the internal transcribed spacer (ITS) and the translation elongation factor 1-a (EF1-a) regions. Species-specific primers for Diplodia sapinea and D. scrobiculata were used to differentiate these fungi. Diplodia scrobiculata was detected on samples from asymptomatic trees, and BLASTN comparison was performed using the NCBI database. Lesions on P. radiata seedlings under controlled conditions were proved to be more substantial from D. scrobiculata than from D. sapinea. This is the first report of virulent D. scrobiculata in asymptomatic P. radiata trees in Spain.
Key words: Pinus radiata, Diplodia shoot blight, asymptomatic, aggressiveness.
Introduction
Diplodia scrobiculata has been reported in Europe and Spain (Stanosz et al., 1999; Moret and Muñoz, 2007). This fungus is known to coexist and interact with D. sapinea, one of the most common fungi found on pine trees (Burgess et al., 2004), but D. scrobiculata has a much more limited distribution and host range (Bihon et al., 2010). In its native range, Pinus radiata D. Don (Monterey pine) has been suggested to be exclusively associated with D. scrobiculata (Burgess et al., 2004). Previous pathogenicity studies have shown D. scrobiculata to be less virulent than D. sapinea (Palmer et al., 1987; Blodgett and Stanosz, 1999; Blodgett and Bonello, 2003), and biocontrol experiments have proved its ability to reduce Diplodia shoot blight (Muñoz et al., 2008). Nevertheless, D. scrobiculata has been reported to be as virulent as D. sapinea in South Africa (Bihon et al., 2010).
This paper presents results which identified the fungal species associated with Diplodia blight in northern Spain.
Material and methods
A survey for incidence of wood fungal pathogens was conducted in Pinus radiata plantations showing Diplodia shoot blight symptoms, located in the Basque Country (northern Spain, 42.989625°N, -2.618927°E). Samples were obtained from diseased and symptomless trees...