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Induction of conifer immune responses by phytopathogenic fungus metabolites

Polyakova, G. G., Pashenova, N. V., Polyakov, V. I., Zrazhevskaya, G. K.
Russian journal of plant physiology 2008 v.55 no.4 pp. 496-502
Abies sibirica, Larix sibirica, Picea obovata, Pinus sibirica, Pinus sylvestris, bark, basidia, conifers, elicitors, hypersensitivity, immune response, lignin, metabolites, mycelium, phloem, plant pathogenic fungi, proanthocyanidins, tree trunk, trees, Siberia
The elicitor activity of compounds extracted from the mycelia of six species of phytopathogenic fungi was assessed from the sizes of necrotic lesions on the external surface of the living trunk phloem of five coniferous species inhabiting Siberia: Siberian larch (Larix sibirica L.), Scotch pine (Pinus sylvestris L.), Siberian spruce (Picea obovata Ledeb.), Siberian fir (Abies sibirica L.), and cedar pine (Pinus sibirica (Rupr.) Mayr.). The compounds for inoculation were extracted from the mycelium of ascomycetes imperfect, and basidium fungi; the living mycelia of these fungi were also used. The fungal extract or mycelium was placed into the hollows 7 mm in diameter in the trunk bark. Infection triggered the formation of hypersensitivity necrotic lesions in the inner bark exceeding in size those appeared after control wounding of four tree species (larch, pine, spruce, and cedar); fir was an exclusion. In experiments with tree trunks and conifer calluses, a dependence of immune response parameters (the sizes of necrotic lesions and the content of lignin and bound proanthocyanidins) on the quantity of the fungal preparation was elucidated. The largest necrotic lesions appeared after injection of 500μg of the fungal preparation into the hollow in the trunk, and its higher quantities did not increase the indices measured. The size of the necrotic lesion on the trunk bark is supposed to be used as a promising index characterizing the level of tree immunity and tolerance under various ecological conditions.