Occurrence and pathogenicity of Corinectria spp. – an emerging canker disease of Abies sibirica in Central Siberia

Abstract

During recent years, a new disease of Siberian fir (A. sibirica) emerged in Central Siberia, exhibiting symptoms of stem/branch deformation, cambium necrosis, and dieback of branches and twigs, the causal agent remaining unknown. The aim was to identify agent of the disease and to investigate its pathogenicity to A. sibirica and Norway spruce (Picea abies). Symptomatic tissues of fir were subjected to pure culture isolation of anticipated pathogen(s). Obtained isolates were subjected to molecular identification, phylogenetic analyses, and pathogenicity tests with A. sibirica saplings, and seeds and seedlings of A. sibirica and P. abies. The study demonstrated that, (i) most commonly isolated fungus from canker wounds of A. sibirica exhibited Acremonium-like anamorphs; (ii) phylogeny demonstrated that investigated fungi belong to genus Corinectria, but are genetically well separated from other worldwide known Corinectria spp.; (iii) one species of isolated fungi has the capacity to cause the disease and kill A. sibirica saplings and seedlings, but also seedlings of P. abies. Guidelines for future research were defined in order to generate needed information on species description, its origin and ecology, and estimation of potential risks upon the eventual invasion of the pathogen to new geographic areas, in particular of Europe. Abies sibirica Ledeb., the Siberian fir, is a very widespread tree species: the range of its native distribution covers a huge geographic area, stretching from Northern Europe-Russia (starting east of the Volga River), through Siberia to northern China, Mongolia, and the Russian Far East, reaching north up to 67°40′ Northern latitude (http://www.agroatlas.ru/en/content/related/Abies_sibirica/map/index.html) (Fig. 1). There, A. sibirica forms extensive forests on the northern plains and on cool wet mountainsides, growing on soils that are usually of alluvial origin, podzolic, calcareous, well drained and free of permafrost; in the mountains, reaching elevations up to 2000 metres. It is an economically important timber species, extensively harvested from vast natural stands for use in construction, pulp etc.; the tree also has local medicinal uses 1. Notably, native range of A. sibirica in the European part of Russia (west of Ural Mountains reaching the Volga River) overlaps with that of Norway spruce (Picea abies (L.) Karst.) (Fig. 1), one of the most economically important timber producing tree species of Europe. During recent years, a new disease of A. sibirica emerged in Central Siberia (Fig. 1), exhibiting symptoms of stem/branch deformation, cambium necrosis, and dieback of branches and twigs, with the subsequent development on those of round red fungal fruitbodies (Fig. 2A-C). The disease is typically observed on relatively young re-growth trees, and often results in their death. The first symptoms of the disease have been observed in the year 2006 in the eastern Sayan Mountains (N54°29′13″; E93°27′11″; elevation 700 m), and after following two years it was repeatedly observed within ...