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Protecting Our Native Caledonian Pine Woodlands

Black Wood of Rannoch

Cultivation of non-native pine trees such as Corsican pine (Pinus nigra) and Lodgepole pine (Pinus contorta) increases the risk of fungal disease transmission when planted next to native Caledonian Scots pine. That’s the conclusion of a research project led by plant researchers at Scotland’s Rural College (SRUC) and the University of Edinburgh.

The research, which was led by Dr Peter Heobe (SRUC) and Honorary Fellow Richard Ennos (University of Edinburgh) examined the fungus (Dothistroma septosporum), which is responsible for needle blight in pine trees*.

The study focussed on collecting hundreds of pine needle samples from pine forests throughout Scotland in order to examine the diversity, distribution and origin of D. septosporum outbreaks in native Caledonian Scots pine.

The results of the study, which were published in the journal ‘Evolutionary Applications’, distinguished three races of D. septosporum: one race of low generic diversity associated with introduced Lodgepole pine, a second race of high genetic diversity associated with introduced Corsican pine and a third race of intermediate diversity apparently endemic to Caledonian Scots pine.

The findings of the investigation appear to demonstrate that the planting of non-native pine woodlands has facilitated the introduction of two exotic races of D. septosporum into Scotland, which pose a threat to native Caledonian pines both directly, and indirectly through potential hybridization and introgression with the endemic race.

Given the growing concerns regarding fungal disease transmission to our native Caledonian pines from non-native pines, the results of the study support the growing movement towards the removal of non-native species from the vicinity of Caledonian pine populations, in addition to a restriction of movement of planting material to minimize the impact of fungal disease outbreaks.

* Needle blight, which has spread rapidly throughout the UK since the early 1990s, is the premature loss of needles from pine trees, which results in the loss of tree growth/yield or in severe case, tree death. Corsican pine is susceptibility to red band needle blight, in addition to other fungal diseases such as Lophodermella needle disease and Brunchorstia shoot dieback. Lodgepole pine is also susceptibility to red band needle blight, in addition to Heterobasidion root and butt rot and Ramichloridium shoot pathogen. Caledonian Scots pine is susceptible to all of the above fungal pathogens.

Information Source: Evolutionary Applications

Image Credit: Forest Commission, Expo Global Database & TETRIX Ecology

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