The problem of induced immunity in conifers

Abstract

During the field experiments on artificial inoculation, the mycelium of Grosmannia aoshimae (Ohtaka et Masuya) Masuya et Yamaoka fungus was observed to spread slowly in the conductive tissues of Siberian fir (Abies sibirica Ledeb.) trees that retained their viability after slow intensity attack by four-eyed fir bark beetles (Polygraphus proximus Blandford). In damaged trees the length of phloem necrosis after artificial inoculation of trunks with G. aoshimae culture was approximately 30 % less than in trees without signs of attack. The most likely reason for the inhibition is the defense reactions presumably induced in stems by unsuccessful attempts of the beetle attack prior to artificial inoculation. This phenomenon raises the question of the lack of knowledge about induced resistance in coniferous species. In contrast to herbaceous plants induced resistance in woody species including coniferous ones has been poorly studied. It was demonstrated that natural or artificial “low-intensity” infection with pathogens can increase tree resistance to diseases in branches and trunks, as well as to stem pests. However, the signaling pathways that cause the activation of defense reactions have not yet been sufficiently characterized. Because of the size of woody plants and the multiplicity of their ecological relationships, it is of particularly importance to study the interactions between molecular signaling pathways that are running from the different sites of damage. Studies of induced resistance in conifers, especially the characterization of endogenous signaling pathways, open the new prospects for tree conditions diagnosing, developing environmentally friendly methods for regulating the resistance of forest stands, mitigating the pest impact on trees, including the cases of biological invasions.

Keywords

• conifers
• phytopathogens
• pests
• induced resistance