Induced plant responses include changes in both volatile and non-volatile secondary metabolites. To investigate the role of bacterial pathogenesis in plant volatile emissions, tobacco plants, Nicotiana tabacum strain K326, were inoculated with virulent, avirulent, and mutant strains of Pseudomonas syringae. Volatile compounds released by inoculated tobacco plants were collected and analyzed. In the incompatible interactions involving P. syringae pv. maculicola ES4326 (Psm ES4326) or pv. tomato DC3000 (Pst DC3000), infected tobacco plants emitted quantitatively different, but qualitatively similar volatile blends of (E)-b-ocimene, linalool, methyl salicylate (MeSA), indole, caryophyllene, b-elemene, a-farnesene, and two unknown sesquiterpenes. Plants treated with the hrcC- mutant of Pst DC3000 (hrcC-, deficient in the type III secretion system) released small quantities of many of the same found in volatiles from Psm ES4326 or Pst DC3000-infected plants, with the exception of MeSA, which was emitted not at all or in trace amounts. A different blend, consisting of only MeSA and two unknown sesquiterpenes was released by plants infected with the virulent P. syringae pv. tabaci (Pstb). Emission of these compounds by infected plant may not only serve as a direct defense against pathogen infections but also affect host recognition by some herbivores.
Keywords: volatile emissions
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