The role of silicon fertilization in the synthesis of phenolic compounds on chestnut plants infected with P. cinnamomi and C. parasitica

Silicon is considered a beneficial nutrient for agricultural crops by conferred protection against diseases. The antifungal effect of the phenolic extracts from chestnut plants treated with 0, 5, 7.5 and 10 mM SiK® was tested in vitro. The results showed that the phenolic extracts from 10 mM SiK®-treated plants presented strongest inhibition zone against P. cinnamomi (10.56 cm2) and C. parasitica (11.2 cm2) in vitro assays at 8 days after incubation. The highest concentration of Si induced the increase in phenylalanine ammonia-lyase and polyphenol oxidase activity in chestnut plants infected with P. cinnamomi and C. parasitica. In addition, the phenolic extracts from Si-treated leaves were analyzed by high-performance liquid chromatography (HPLC–DAD) and the compounds identified were gallic acid, gallic acid derivate, vescalagin, castalagin, 1-O-Galloyl castalagin, chlorogenic acid, coumaric acid, syringic acid, vanillic acid, ellagic acid, quercitin-3-O-rutinoside and apigenin. The main phenolic compounds found in Si-treated plants (10 mM SiK®) were castalagin, gallic acid and its derivatives with an increase of 463%, 244% and 274%, respectively, when compared with untreated plants which can be correlated with the induction of resistance in chestnut plants against phytopathogenic agents studied. The present study provides the evident antifungal activity of the phenolic extracts from plants treated with concentrations of 7.5 and 10 mM SiK® in vitro assays suggesting that Si application can be useful in the future to control the ink disease and chestnut blight in this crop.