Magnesium carbonate elicits defense-related genes in King Ruby grapevines against downy mildew and improves its...

Downy mildew, caused by Plasmopara viticola (Berk. and M. A. Curtis) Berl. and De Toni, is a serious disease of grapevines in general and King Ruby seedless cultivar in particular, affecting their growth and yield. Magnesium carbonate (MgCO₃) is an antitranspirant, which induces stomatal closing and enhances plant growth and physiology. In this study, effect of foliar application of MgCO₃ at 1 and 3% on plant resistance, growth, yield and physiology of grapevines (cv. King Ruby seedless) infected with downy mildew was investigated under field conditions. The obtained results showed that foliar application of MgCO₃ at 3% led to upregulation of the transcription factor JERF3 (9.6-fold), and the defense-related genes GLU (6.3-fold), POD (8.7-fold), PR1 (9.6-fold), and CHI II (8.6-fold). In addition, this treatment led to a reduction in the disease severity (78%), and an increment in the yield per grapevine (20%). Furthermore, biochemical properties of berries, total contents of the photosynthetic pigments, phenolic compounds, and activities of the antioxidant enzymes peroxidase and polyphenol oxidase also enhanced. In contrast, lipid peroxidation, and H₂O₂ content in grapevines leaves reduced in response to MgCO₃ spraying. Light microscope observations revealed that average number of closed stomata increased and the average stomatal pore area decreased in grapevines leaves as a result to MgCO₃ spraying. Based on these results, we can conclude that spraying with MgCO₃ at 3% has effective roles in inducing the plant resistance against downy mildew, and improving the growth and yield of grapevines.