Studies on the causal agents, distribution and host range of red band needle blight
During the last decades, serious outbreaks of red band needle blight have increasingly been reported from different parts of the world, in particular on Pinus radiata in the Southern hemisphere (e.g. Chile, Kenya, New Zealand), and in the Northern hemisphere on P. nigra subsp. laricio in France and the United Kingdom, on P. contorta var. latifolia in British Columbia (Canada), and on P. nigra in Hungary and the Czech Republic. Until recently, the cause of red band needle blight was attributed to Dothistroma septosporum (teleomorph Mycosphaerella pini – EU Annexes) and the name Dothistroma pini was considered as a synonym. However, comparison studies of DNA sequences (32 isolates from 13 countries) have demonstrated that two distinct fungal species were associated with the disease: Dothistroma septosporum (teleomorph Mycosphaerella pini) and Dothistroma pini (teleomorph unknown). These two species present some small differences in conidial morphology and dimensions but these characteristics cannot be used to differentiate them reliably. D. septosporum and D. pini can be distinguished on the basis of DNA sequence comparisons of nuclear gene regions (rDNA ITS, β-tubulin, TEF 1-α).
During these comparison studies, both pathogens have been detected on new hosts and from new countries. D. septosporum has been detected in Austria on P. peuce (new host record), on P. mugo in Hungary, on P. radiata and P. wallichiana (new host record) in Bhutan (new country record). To date, D. pini has been identified on Pinus nigra in USA (Illinois, Nebraska, Michigan and Minnesota) where it is causing severe damage, particularly in Christmas tree plantations. D. pini has also been detected on P. pallasiana (similar to P. nigra and considered by some authors as P. nigra var. pallasiana) in Ukraine and Russia. In Ukraine, D. pini has been detected near Tsyurupinsk (Kherson Oblast). In Russia, D. pini has been detected in 2 localities near Rostov (Southern Russia). It is noted that since 2004, red band needle blight has become a problem in P. pallasiana forests in Ukraine and South-Western Russia. The disease is noticeable on P. pallasiana in the Rostov and Volgograd regions and its distribution expands to most areas which are located along the basins of the Don and Donets rivers, as well as the Belaya Kalitva and Chir rivers. But in these regions it is not known whether D. pini occurs alone or in combination with D. septosporum. Further studies are now needed to better understand the geographical distribution and host range of both pathogens, and their respective role in the disease severity.
Sources
Barnes I, Crous PW, Wingfield BD, Wingfield MJ (2004) Multigenes phylogenies reveal that red band needle blight of Pinus is caused by two distinct species of Dothistroma, D. septosporum and D. pini. Studies in Mycology 50, 551-565.
Barnes I, Kirisits T, Akulov A, Chhetri DB, Wingfield BD, Bulgakov TS, Wingfield MJ (2008) New host and country records of the Dothistroma needle blight pathogens from Europe and Asia. Forest Pathology 38(3), 178-195.
Barnes I, Wingfield MJ, Groenewald M, Kirisits T, Crous PW, Wingfield BD (2007) Exposing the enigma of Dothistroma needle blight using molecular markers – a progress report. Acta Silvica and Lignaria Hungaria, special edition, 239-240.