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Ethylene Production in Pinus radiata in Response to Sirex-Amylostereum Attack. Louis Shain, Senior Research Scientist, Forest Products Laboratory, Division of Applied Chemistry, CSIRO, South Melbourne, Victoria 3205, Australia, Present address of senior author: Department of Plant Pathology, University of Kentucky, Lexington 40506; W. E. Hillis, Chief Research Scientist, Forest Products Laboratory, Division of Applied Chemistry, CSIRO, South Melbourne, Victoria 3205, Australia. Phytopathology 62:1407-1409. Accepted for publication 15 June 1972. DOI: 10.1094/Phyto-62-1407.

Ethylene production was demonstrated in the sapwood of Pinus radiata which was mechanically injured or attacked by the wood wasp Sirex noctilio. Ethylene produced by the symbiotic fungus Amylostereum areolatum, which is inoculated into the tree at the time of oviposition, was negligible. Sirex lesions 1 to 4 weeks old in dominant trees produced significantly more ethylene than mechanically induced lesions or controls (42.3, 13.3, and 2.5 × 10^–9 liter C₂H₄/g dry wood per hr, respectively). Similar figures for a suppressed tree were 4.6, 9.0, and 2.2 × 10^–9 liter C₂H₄/g dry wood per hr. Trees which produced large quantities of ethylene in response to attack produced greater quantities of inhibitory phenols at a faster rate. The amount of ethylene produced may be a convenient and rapid means of distinguishing a susceptible from a resistant response. If heritable, the ability to produce large quantities of ethylene in response to attack may be a valuable parameter in breeding for disease resistance.