Abstract
The claim that organic agriculture produces higher levels of phytochemicals has been controversial for decades. Using strawberries as a model crop in field conditions, a preharvest leaf wounding stress was applied to study the production of phytochemicals in fruits. As a result phenolic compounds (PCs) and total soluble sugars increased significantly, where specific phenylpropanoids showed increment up to 137% and several genes related to PCs biosynthesis and sugar transport were overexpressed. It was observed that the accumulation of PCs on fruits can be triggered by the application of wounding stress in a distant tissue and this accumulation is directly related to carbon partition and associated gene expression. This supports the idea that higher levels of healthy phytochemicals reported in organic fruits and vegetables could be due to the wounding component of the biotic stress attributed to insects to which the plant are exposed to.
Highlights
The organic food market have grown between 17% and 21% in the last years, compared to the 2–4% growth for conventional food products market[1]
In the present study we evaluated the systemic induction of secondary metabolites in fruits when the stress is applied in a distant organ of the plant and proposed a mechanism of phenylpropanoid accumulation in the fruit and how it is directly related to carbon partition and associated gene expression
Based on the results found in the present study and on previous research, we propose a model explaining the possible mechanism of polyphenol biosynthesis in strawberries as a result of distant wounding stress exerted in the plant leaves (Fig. 5)
Summary
The organic food market have grown between 17% and 21% in the last years, compared to the 2–4% growth for conventional food products market[1]. European countries and United States lead the global market as producers and consumers, and several other countries, including Australia, China, Argentina, Brazil and Uruguay are important producers for export markets[2] Studies evaluating secondary metabolite responses to biotic stress have shown an induction of phenolic compounds production and other phytoalexins as a local and systemic plant defensive response; these studies were conducted in the same tissue where the damage had been caused by piercing-sucking insects[9,19] or leaf chewing insects[20,21]. In the present study we evaluated the systemic induction of secondary metabolites in fruits when the stress is applied in a distant organ of the plant (e.g., leaves, Fig. 1) and proposed a mechanism of phenylpropanoid accumulation in the fruit and how it is directly related to carbon partition and associated gene expression
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