Antioxidant defences of Norway spruce bark against bark beetles and its associated blue-stain fungus

Bark beetles and their fungal associates are integral parts of forest ecosystems, the European spruce bark beetle (Ips typographus Linnaeus, 1758) and the associated pathogenic blue stain fungus Ceratocystis polonica (SIEM.) C. MOREAU, are the most devastating pests regarding Norway spruce [Picea abies (L.) H. KARST.]. Bark beetles commonly inhabit weakened and felled trees as well as vital trees. They cause physiological disorders in trees by destroying a phloem and cambium or interrupt the transpiration -ow in the xylem. Conifers have a wide range of effective defence mechanisms that are based on the inner bark anatomy and physiological state of the tree. The basic function of bark defences is to protect the nutrient-and energy-rich phloem, the vital meristematic region of the vascular cambium, and the transpiration -ow in the sapwood. The main area of defence mechanisms is secondary phloem, which is physically and chemically protected by polyphenolic parenchyma (PP) cells, sclerenchyma, calcium oxalate crystals and resin ducts. Conifer trunk pest resistance includes constitutive, inducible defences and acquired resistance. Both constitutive and inducible defences may deter beetle invasion, impede fungal growth and close entrance wounds. During a successful attack, systemic acquired resistance (SAR) becomes effective and represents a third defence strategy. It gradually develops throughout the plant and provides a systemic change within the whole tree’s metabolism, which is maintained over a longer period of time. The broad range of defence mechanisms that contribute to the activation and utilisation of SAR, includes antioxidants and antioxidant enzymes, which are generally linked to the actions of reactive oxygen species (ROS). The presented review discusses the current knowledge on the antioxidant defence strategies of spruce inner bark against the bark beetle (Ips typographus) and associated blue stain fungus (Ceratocystis polonica).

Induced wound response of Norway spruce Picea abies P. Karst. after artificial inoculation by imagoes of Ips typographus

Inoculation experiments were carried out on a set of trees with imagoes of Ips typographus L. which origin from the Šumava Mts. and the Křtiny Training Enterprise. The objective of back inoculations was to determine whether species found on the surface of Ips typographus imagoes spread after the inoculation also through host tissues. It the vicinity of inoculation by Ips typographus imagoes, marked necrotic zones are evident including symptoms of the penetration of vascular pathogens through phloem and sapwood. The most marked reactions were observed in case of inoculation by an untreated Ips typographus imago. Treatment of Ips typographus imagoes by Ibefungin and Fundazol preparations did not demonstrate expected effects in full scale. The spores of several ophiostomoid fungi like Ceratocystis polonica (Siem.) C. Moreau were observed on the surface of bark beetles and at the same time were re-isolated from wounds inoculated by Ips typographus imagoes. The other fungi like Ophiostoma bicolor Davidson & Wells, Leptographium cf. lundbergii Lagerberg & Melin., Pezicula eucrita Karst., Phomopsis sp. and other were found in wounds with the imagoes artificial infection.