Wounding response in xylem of Scots pine seedlings shows wide genetic variation and connection with the constitutive defence of heartwood

Abstract

In this greenhouse experiment, 3-year-old Scots pine (Pinus sylvestris L.) seedlings were wounded by drilling holes through the stem. In the xylem next to the wound, the concentration of resin acids (RAC) increased, and the production of extractives typical for heartwood (stilbenes) and knotwood (stilbenes and lignans) of mature trees was induced. The induced stilbenes were pinosylvin (PS) and pinosylvin monomethyl ether (PSM), and the lignans nortrachelogenin (NTG) and matairesinol (MR). There was positive phenotypic correlation between concentrations of the different extractives. Except for the RAC, the extractive concentrations showed no correlation with the size of the seedlings. The treated seedlings belonged to half-sib families, which enabled the estimation of the genetic parameters for the response variables. The proportion of heritable variation (heritability, h(2)) in the concentration of PS, NTG and MR varied between 0.71 and 1.03, whereas for PSM and RAC the heritability was lower (0.35 and 0.31). Genetic correlation was significant between PS and PSM (r = 0.55, P = 0.018), and between NTG and MR (r = 0.50, P = 0.033). Heritabilities were also estimated on the basis of the regression of the offspring on their mothers h(2)(0P). These estimates were assessed for the concentration of PS, PSM and RAC in the wound response area of the seedlings and correspondingly in the heartwood of their mothers. The heritability was highest for the concentration of PS h(2)(0P). The findings of this study support the suggestion that the wounding of Scots pine seedlings may facilitate the development of an early testing method for breeding heartwood durability.

Phenolic compounds in Scots pine heartwood: are kelo trees a unique woody substrate?

“…Karppanen et al (2008) measured rapid concentration declines of both PS and PSM with increasing mass loss of Scots pine heartwood decayed by the brown-rot Coniophora puteana. They concluded this fungus was capable of eliminating these two compounds, even though they have been identified as playing a major part in heartwood decay resistance (e.g., Venäläinen et al 2004;Harju et al 2009). This interpretation fits our observations here as well.…”

Regulation of stilbene biosynthesis in plants

“…Rudolf and Resurreccion (2005) found that slicing of peanut kernels increased production of t-resveratrol. Harju et al (2009) report that wounding caused by drilling holes through the stem of Scots pine induced the production of pinosylvin and pinosylvin monomethyl ether.…”

The O‐methyltransferase PMT2 mediates methylation of pinosylvin in Scots pine

“…For wounding experiments, 5-yr-old Scots pine seedlings were used. Seedlings were grown in the glasshouse and wounded by drilling through the stem as described by Harju et al (2009). Xylem samples were collected 3 h (3H), 24 h (1D) and 96 h (4D) after wounding.…”

“…The transition zone corresponds to a narrow, one to two growth ring wide zone in the wood where the transition of sapwood into heartwood is occurring (Lim et al, 2016). Stilbene production is known to be induced in response to UV-C and wounding stresses, in addition to developmental regulation during heartwood formation (Schoeppner & Kindl, 1979;Bergstr€ om, 2003;Harju et al, 2009). Transcripts encoding the Scots pine stilbene synthase (STS) were strongly upregulated in these conditions; however, when we analyzed the expression profile of the previously described pinosylvin methylating enzyme-encoding PMT1 (Chiron et al, 2000a) in our transcriptome libraries, it was either not expressed at all or not coregulated with STS ( Fig.…”