Use of plant growth regulators to increase polyphenolic compounds in the wild blueberry

Abstract

With increasing awareness of the antioxidant properties of the wild blueberry (Vaccinium angustifolium Ait.), more emphasis has been placed on d eveloping cultural management practices to enhance fruit polyphenolic levels and the use of processing byproducts as potential polyphenolic sources for the nutraceutical market. Trials were initiated in 2004 and 2005, with four plant growth regulators (methyl jasmonate, abscisic acid, riboflavin and Retain®) applied to maturing berries of the select clone Fundy at the Wild Blueberry Research Centre (Debert, NS). Berries were harvested 3 wk after treatment applications, with collections of green leaf tissues at harvest and red leaf tissues two weeks after harvest in 2005. Assessment of polyphenolic and anthocyanin levels within the berry and leaf tissues followed the Folin-Ciocalteu and pH differential methods, respectively. Overall, substantially higher levels of polyphenolic compounds were found within the leaf tissues, although anthocyanin content was highest in the berries. The application of methyl jasmonate resulted in a minor elevation in levels of bioactives within the harvested berry and red leaf tissues. This increase in bioactives occurred, however, at the expense of harvestable yields, with lower yield in plots treated with methyl jasmonate in 2004. Results thus suggest that the use of some plant growth regulators (PGR) may serve to increase bioactives, but their value must be assessed against a possible yield reduction. In addition, these studies indicate that leaf debris may provide a superior polyphenolic source for the nutraceutical market. Key words: Wild blueberry, plant growth regulator, anthocyanins, polyphenolics