Influence of elevated CO concentration on disease development in tomato.

•  Changes are reported here in Phytophthora parasitica (root rot) infection of Lycopersicon esculentum (tomato) in response to elevated CO concentration. •  Defense-related gene expression in tomato infected with P. parasitica was measured in plants grown at ambient (350 ppm) and elevated (700 ppm) CO . •  Tomato plants showed a degree of tolerance against P. parasitica at elevated [CO ] but there was no significant difference in pathogenesis-related (PR) or wound-response gene expression. In response to P. parasitica, PR mRNAs increased in infected roots of plants grown at elevated [CO ] while wound-reponse gene mRNAs were not induced. By contrast, increases in PR mRNAs and wound-responses transcripts in leaves correlated with increases in salicylic acid and abscisic acid, respectively. The [CO ] had little effect on the timing or levels of both PR and wound-response mRNAs in infected plants. •  Tomato plants show a degree of tolerance against P. parasitica at elevated [CO ]. This tolerance might be due to the effect of carbon dioxide (CO ) concentration on the transcription or post-translational turnover of PR proteins, or through increased photosynthesis and water use efficiency.