Phenol metabolism of two cultivars of durum wheat (Triticum durum Desf.) as affected by ozone and flooding stress

To compare the phenolic responses under oxidative stressors, plants of two Italian cultivars of durum wheat (Claudio and Mongibello) were (a) exposed to ozone (O-3) (80 ppb, 5 hr/day for 70 consecutive days), with the aim to investigate the changes of phenolic compound contents in their leaves, or (b) flooded (seven consecutive days). Plants showed O-3-induced visible injury, but their photosynthetic performance was not affected by the pollutant. Specifically, Claudio showed a higher O-3 tolerance than Mongibello. The major value of the present study is undoubtedly the pioneering investigation of phenolic metabolism of durum wheat under O-3. We identified 12 foliar phenolic compounds in all leaf samples (i.e. controls, exposed to O-3 and flooded): ten phenolic acids, a flavanol (catechin hydrate) and a phenolic aldehyde (syringaldehyde). Overall, O-3 exposure resulted in accumulations of phenolic compounds, especially in Claudio. These responses can be likely considered a fine-regulated repair process that equipped Claudio stressed plants with an antioxidant system capable of scavenging oxidative stress. Different phenolic variations were found in flooded plants, suggesting that phenolic response to environmental constraints is stress specific. Our study confirms that investigations and characterization of specific phenolic profiles of crop cultivars under oxidative stress may be helpful in breeding programmes.