Quality and PR gene expression of table grapes treated with ozone and sulfur dioxide to control fungal decay.

Background: Gaseous fumigants are commonly employed to control fungal decay of cold-stored grapes. So far it is not clear if these fumigants, besides the direct interaction against fungal structures, induce transcriptional responses of defensive markers. In order to contribute to understanding the mechanisms by which these fumigants exert their effect, we studied the influence of ozone (O3) and sulfur dioxide (SO2) on the decay caused by Botrytis cinerea, and the quality and expression of the defense-related genes chitinase, β-1,3-glucanase and phenylalanine ammonia-lyase (PAL) in the table grape cultivars 'Redglobe' and 'Sugraone'.

Results: The application of SO2 or O3 delayed decay of both table grape cultivars caused by B. cinerea compared with the inoculated control. O3 treatments altered weight loss, firmness and shatter in both cultivars. Significant upregulation of chitinase and β-1,3-glucanase were observed in SO2 -treated 'Redglobe' berries stored at 2 °C. O3 treatment transiently increased the expression of chitinase and PAL in 'Redglobe' and 'Sugraone' berries, respectively.

Conclusion: Ozone and sulfur dioxide treatments can influence the expression patterns of PAL, chitinase and β-1,3-glucanase to different extents in different grape cultivars and under different exposure conditions. The upregulation of these genes may be involved in the mechanism by which these fumigants inhibit the decay caused by pathogenic fungi.