Systemic induction of traumatic resin ducts and resin flow in Austrian pine by wounding and inoculation with Sphaeropsis sapinea and Diplodia scrobiculata

Abstract

The potential role of the resin system in the response of Austrian pine (Pinus nigra Arn.) seedlings to mechanical injury and fungal infection was studied in greenhouse experiments. Anatomical observations were performed on 2-year-old plants wounded at collar level and inoculated with Sphaeropsis sapinea (Fr.: Fr.) Dyko & Sutton in Sutton or Diplodia scrobiculata (J. de Wet, B. Slippers & M. J. Wingfield, sp. nov.; sensu de Wet et al. 2003), two fungal pathogens that cause shoot blight and canker on conifers, and that are characterized by different levels of aggressiveness. Histological examination of host tissue taken from the stem at 0, 8, and 12 cm above the treatment site revealed significant treatment- and time-dependent effects on the course of locally and systemically induced traumatic resin duct (TRD) development. Occurrence of TRDs was observed after 4 days only in seedlings inoculated with D. scrobiculata. At 12 days, TRDs were present also in mock-inoculated controls. No TRDs appeared in seedlings inoculated with S. sapinea. However, S. sapinea caused loss of vacuolar phenolics, severe disruption of cambial tissue and invaded the host xylem quickly and apparently unimpeded, whereas D. scrobiculata was never detected in the host xylem. Five-year-old Austrian pines subjected to the same stem base treatments were used to determine the resin mass flowing from the stem 30 cm above the treatment sites. Wounding and/or inoculation induced a significant, 8.3-fold average increase in systemic resin flow over the untreated trees 3 weeks after basal treatment, suggesting that wounding is the sole prerequisite for systemic induction of resin flow. The results are discussed in the context of current disease resistance models.

Resin Flow, Symptom Development, and Lignin Biosynthesis of Two Pine Species in Response to Wounding and Inoculation with Fusarium circinatum

“…The same letters denote no significant difference at P = 0.01 according to FLSD test. (Luchi et al, 2005). Concomitantly, the results of lignin content were consistent with those of resin flow from the two pine species, showing a higher increase in lignin content from the woundinoculated bark and the pre-wounding wound-inoculated bark than any other treatments.…”

“…Conifers are all characterized by secondary growth, which gives a complicating factor of more complex growth than annual angiosperms commonly used in most host-pathogen studies (Hammerschmidt, 2006). Exposed to mechanical injury and attacks by numerous pathogens and insects, conifers deploy various defense mechanisms as other plants (Luchi et al, 2005). Constitutive production of either structural defense products such as cuticle and periderm or biochemical defense products such as phenolics and terpenoids provides a generalized defense against a broad range of organisms (Franceschi et al, 2005).…”

“…Constitutive production of either structural defense products such as cuticle and periderm or biochemical defense products such as phenolics and terpenoids provides a generalized defense against a broad range of organisms (Franceschi et al, 2005). Synthesized in specialized secretory structures called resin cells and resin ducts, resin is known to act primarily as a wound cleanser and sealant, and also shown to have antimicrobial activity (Luchi et al, 2005). Oleoresin (a mixture of monoterpenes, resin acids, and neutral compounds) is the most obvious and widespread resin of coniferous trees, providing a chemical and physical barrier against biotic intrusions (Lombardero et al, 2000(Lombardero et al, , 2006.…”

Monoterpene responses to interacting effects of drought stress and infection by the fungus Heterobasidion parviporum in two clones of Norway spruce (Picea abies)

“…This mechanism occurs not only in herbaceous plants (Durrant and Dong, 2004), but also in different conifer tree species (Bonello et al, 2001;Bonello and Blodgett, 2003;Luchi et al, 2005;Wallis et al, 2007).…”

Tree-ring analysis in natural hazards research – an overview

“…In contrast, resin ducts are not produced in traumatic and tangential rows in pine trees and cannot therefore be used for the dating of past ge- omorphic events, as this genus produces copious amounts of resin without necessarily suffering from mechanical wounding (Phillips and Croteau, 1999). Given that wounding occurred during the vegetation period of the tree, resin production will start only a few days after the event and axial ducts will emerge within less than three weeks after the disturbing event (Ruel et al, 1998;McKay et al, 2003;Luchi et al, 2005). When analyzing cross-sections, the intra-seasonal position of the first series of TRD can, therefore, be used for the reconstruction of previous events and with monthly precision Stoffel and Beniston, 2006;Stoffel, 2008), provided that the incidence occurred during the vegetation period.…”