engleski

Flavescence dorée phytoplasma infection induces changes to the phenolic profile of 'Pinot noir' (Vitis vinifera L.) leaves

Phytoplasmas (genus ‘Candidatus Phytoplasma’) are uncultivable bacterial intracellular parasites of plants, as well as insects, which act as vectors for their dispersal. They cause heavy damage to agricultural production worldwide. Among infecting other agriculturally important plant species, they are known to heavily affect viticultural production. Two phytoplasmas have been identified as causative agents of grapevine yellows diseases, one of which is the flavescence dorée phytoplasma (FDp), a quarantine pathogen in many countries. Due to the inability to cultivate phytoplasmas in a pure culture in vitro, phytoplasma research faces many challenges. In this study, we sampled the leaves from symptomatic and asymptomatic grapevine (Vitis vinifera L.) var. ‘Pinot noir’ from a vineyard in central continental Croatia at three time points during the development of infection. Infection of symptomatic plants with FDp was successfully confirmed using a multiplex real-time PCR assay, developed for simultaneous detection of both phytoplasma species causing the grapevine yellows disease. In order to analyse and compare the phenolic content of infected and uninfected grapevine leaves, extraction of phenolic compounds was carried out with 70% (v/v) ethanol. Using various spectrophotometric assays, content of total phenolics, flavonoids, hydroxycinnamic acids, flavanols, catechins, proanthocyanidins and tannins was analysed. Results revealed a high dynamic of the content of analysed groups of phenolic compounds in grapevine infected by the FDp through the development of infection. Several groups of phenolic compounds whose content increased in infected leaves compared to uninfected were identified as potential protective compounds against FDp infection. Severe changes to the phenolic compounds content in infected grapevine leaves compared to the uninfected leaves point the phenolics biosynthesis being a target of FDp effector molecules which interfere with the host physiological processes, because of the potential of phenolic compounds as protective molecules against phytoplasma infection.

flavescence dorée ; phytoplasmas ; phenolics ; specialized metabolism

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