sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDÜ Faculty of Forestry Journal
Two groups, A and B, were distinguished within S. sapinea sensu lato (Palmer
et al., 1987) based on several characteristics such as morphology, growth, virulence
and molecular markers (Palmer et al., 1987; Smith and Stanosz, 1995; de Wet et
al., 2000; Burguess and Wingfield, 2001). Recently, the B group has been
recognized as a distinct species and assigned the name Diplodia scrobiculata J. de
Wet, B. Slippers & M. J. Wingfield (de Wet et al., 2003). At the same time, the A
group was named as Diplodia pinea (Desmaz.) J. Kickx fil. (syn. Sphaeropsis
sapinea (Fr.:Fr.) Dyko & Sutton in Sutton) (de Wet et al., 2003). In terms of
pathogenicity, D. pinea has been shown to be more aggressive than D. scrobiculata
(Blodgett and Stanosz, 1997; Blodgett and Bonello, 2003).
The reported geographic and host ranges of D. pinea and D. scrobiculata are
broad and overlapping. Not only do distributions and hosts overlap, but D. pinea
and D. scrobiculata also are known to occur together. In this sense, both species
have been isolated from individual red pine (Pinus resinosa Aiton.) plantations
(Palmer, 1991; Stanosz et al., 2005) or even from a single tree (Morelet and
Chandelier, 1993) or a single sample (Smith and Stanosz, 2006). Those
experiments stated the potential for intimate association between D. pinea and D.
scrobiculata within host tissues, but relatively little is known about their local cooccurrence
and the implications of this fact for the disease development, and
subsequent survival.
Complete eradication of the pathogen is difficult due to latent infection of
symptomless tissues of apparently healthy trees (Flowers et al., 2001; Stanosz et
al., 2005; Maresi et al., 2007; Stanosz et al., 2007); however, proper control
measures could reduce the spread and virulence of the disease. Among those
measures, the use of biological control is of increasing interest since it provides an
effective and environmentally safer alternative to chemical application. Several
microorganisms, mainly fungi, have been observed to cause ‘systemic induced
resistance’ in the host after their inoculation into the plant, which may prompt a
lower host susceptibility to later infections with D. pinea (Luchi et al., 2005;
Blodgett et al., 2007; Muñoz et al., 2008). On the other hand, several endophytes,
which have been shown to produce secondary metabolites, some of them with
antifungal properties (Tan and Zou, 2001; Schulz et al., 2002), have shown
antagonism with several pathogens and they have been assessed as biological
control agents (Mehrotra et al., 1988; Holdenrieder and Greig, 1998; Roy et al.,
2001). However in the literature, few studies dealing with the use of endophytes as
biological control agents against D. pinea can be found.
Therefore, the main aim of the study was to analyse the effect of D.
scrobiculata and several fungal endophytes, isolated from healthy shoots of Pinus
resinosa and P. banksiana Lamb. (jack pine) adult trees, on the symptom severity
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