Mateja FELICIJAN, Metka NOVAK, Nada KRAŠEVEC, Andreja URBANEK KRAJNC

pp. 9-18

ABSTRACT

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 flow 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 flow 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).

Key words: antioxidants, ascorbate-glutathione system, blue-stain fungus Ceratocystis polonica (SIEM.) C. MOREAU, Norway spruce (Picea abies (L.) H. KARST.), phenolics, systemic acquired resistance (SAR)

Slovenian:

ni obrambni odziv lubja navadne smreke ob napadu podlubnikov in z njimi povezanimi glivami modrivkami

Čeprav so podlubniki in z njimi povezane glive sestavni del gozdnih ekosistemov, sta osmerozobi smrekov lubadar (Ips typographus Linnaeus) in z njim povezana patogena gliva modrivka [Ceratocystis polonica (Siem.) C. Moreau], ena najbolj uničujočih škodljivcev navadne smreke [Picea abies (L.) H. Karsten]. Lubadarji navadno naseljujejo oslabela in podrta drevesa, v specifičnih pogojih pa lahko napadejo tudi vitalna. S poškodbami floema in kambija ter motnjo transpiracijskega toka v ksilemu, drevesu povzročijo številne fiziološke motnje. Iglavci imajo široko paleto obrambnih mehanizmov, ki temeljijo na anatomiji lubja in fiziološkem stanju drevesa. Njihova osnovna funkcija je zaščita hranilno in energetsko bogatega floemskega tkiva, meristematske aktivnosti vaskularnega kambija in transpiracijskega toka v sekundarnem ksilemu debla. Glavno področje obrambnih mehanizmov je namreč sekundarni floem, ki predstavlja fizično in kemično zaščito lubja pred škodljivci, saj vsebuje polifenolne parenhimatske celice, sklerenhim, kristale kalcijevega oksalata in shizogene smolne kanale. Obrambni sistem lubja iglavcev zajema tri vrste obrambnih strategij – konstitutivno in inducirano obrambo ter sistemsko pridobljeno odpornost. Konstitutivna in inducirana obramba zavirata kolonizacijo podlubnikov, rast gliv in zapirata ranitvena mesta. Med uspešnim napadom pa je za drevo ključnega pomena še vzpostavitev sistemsko pridobljene odpornosti (SAR). Le ta se postopoma širi po rastlini ter izzove sistemske spremembe v metabolizmu drevesa, ki se ohranjajo skozi daljše časovno obdobje. Med številnimi obrambnimi odzivi, povezanimi z aktivacijo SAR, sta pomembni sinteza antioksidantov in aktivacija antioksidativnih encimov, ki varujejo rastlino pred reaktivnimi kisikovimi spojinami (ROS). Prispevek zajema pregled dosedanjega znanja o strategijah antioksidativnega odziva lubja smreke pri napadu smrekovega lubadarja (Ips typographus) in z njim povezane patogene glive modrivke (Ceratocystis polonica).

Ključne besede: /

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