Jonathan Rodrigue


Usage of a prophylactic treatment with potassium silicate to control strawberry diseases and to increase strawberry nutraceutic value
The main objective of this project is to verify whether treatment with potassium silicate can induce the accumulation of phenolic products and flavonoids in the leaves and fruit of strawberry plants. To test this hypothesis, plots of conventional and day-neutral strawberries will be planted in the spring of 2004 and kept in place until fall 2005. Foliar treatments with potassium silicate will begin in the spring of 2004, with the appearance of the first leaves, and continue at varying frequencies and durations depending on the cultivar. The varieties used will be Yamaska, L'Acadie, Kent, Orleans, St-Jean Orleans and St-Laurent Orleans in the case of conventional strawberry plants, and Seascape and Aromas in the case of day-neutral strawberry plants. Four distinct treatments per cultivar will be applied: Control; 8 mM Si + 16 mM K; 16 mM Si + 0 mM K; and 0 mM Si + 32 mM K. A split plot design will be used, with 10 plants per experimental unit. The data collected will be divided into three different categories. Initially, the effects of the silica will be evaluated on growth and yield by measuring the wet and dry weight of the leaves, petioles, crowns and roots. In this same category, the photosynthetic activity will be measured three times during the vegetation period with a LI-COR 6400 infrared spectrophotometer. Then, the effect of the silica on disease will be evaluated. Initially, symptoms of diseases such as powdery mildew, anthracnose and gray mold will be evaluated, if they develop in the field, by assessing the incidence of disease expression vs. treatment. Then, the development time of gray mold caused by Botrytis cinerea during post-harvest storage at 4 C for 14 days will be evaluated. Finally, the silica content will be evaluated in different parts of the plant at the end of the season. The fruit's silica, phenolic acid, ellagic acid, flavonol, catechin, epicatechin, proanthocyanidin and anthocyanin content will be evaluated. According to the literature, there should be a direct correlation between the silica content of the plant and fruit, the quantity of phenolic products and flavonoids, and the plant's and fruit's ability to better resist different diseases. Once completed, this experiment will enable confirmation of whether foliar treatments with potassium silicate can reduce the incidence of disease in Fragaria x ananassa Duch., via the accumulation of phenolic products and flavonoids, and also increase the nutraceutical value of the fruit for the consumer.