© 2007 Heron Publishing—Victoria, Canada
Organ-dependent induction of systemic resistance and systemic susceptibility in Pinus nigra inoculated with Sphaeropsis sapinea and Diplodia scrobiculata
James T. Blodgett (1, 2, 3), Alieta Eyles (1) and Pierluigi Bonello (1)
1. Department of Plant Pathology, The Ohio State University, Columbus, OH 43210, USA / 2. USDA - Forest Service, Forest Health Management, Rapid City, SD 57702, USA / 3. Corresponding author (jblodgett@fs.fed.us) / Received April 21, 2006; accepted July 18, 2006; published online January 2, 2007
Summary
Systemic induced resistance (SIR) is a well-known host defense mechanism against pathogen attack in herbaceous plants, but
SIR has only recently been documented in conifers. We tested if inoculation of Austrian pine (Pinus nigra Arnold) with Sphaeropsis sapinea (Fr.:Fr.) Dyko and Sutton or Diplodia scrobiculata de Wet, Slippers and Wingfield results in SIR or systemic induced susceptibility (SIS) to subsequent colonization by S. sapinea. Induction at the stem base resulted in significant (P < 0.01) SIR in the upper stem, and induction in the upper stem resulted
in significant (P < 0.05) SIR at the stem base, indicating that SIR is bidirectional in Austrian pine. However, inoculation
at the stem base resulted in significant (P < 0.01) SIS in shoot tips, demonstrating that, in the same host species, the expression
of resistance can be organ-dependent, resulting in either SIR or SIS depending on the site of challenge infection. Systemic
induced resistance in the stem was associated with induced lignification, supporting a potential role for this defense mechanism
in disease resistance. Systemic induced susceptibility has been documented before, but this is the first demonstration of
organ-dependent expression of both SIR and SIS in a tree or any other plant.
Keywords:
Diplodia pinea, fungal pathogen, host defense, HPLC, lignification, predisposition, secondary metabolism, SIR, SIS, systemic induced resistance,
systemic induced susceptibility.
