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American elderberry (Sambucus canadensis) is a plant native to North America with anthocyanin-rich fruits. Our objective was to investigate the effects of cultivar and ripeness on the phytochemical characteristics of its fruits and the corresponding color performance. Cultivars ‘Adams’, ‘Johns’, ‘Nova’, ‘Wyldewood’, and ‘York’ were examined for their °Brix, pH, anthocyanin (pH-differential method), and phenolic content (Folin-Ciocalteau method). Extract composition were analyzed by uHPLC-PDA-MS/MS. Color and spectra were determined using a plate reader. All characteristics evaluated were significantly affected by ripeness and cultivar, except for °Brix and total phenolic content, which did not vary significantly among cultivars. Most anthocyanins (63–72%) were acylated with p-coumaric acid, with cyanidin-3-(trans)-coumaroylsambubioside-5-glucoside the most predominant. The proportion of acylated anthocyanins was the only characteristic evaluated that decreased during ripening (from 80 to 70%). Extract from fully-ripened fruits exhibited red (lvis-max ~520 nm) and blue hues (lvis-max ~600 nm) at acidic and alkaline pH, respectively. Extracts from half-ripe fruit rendered yellowish tones and overall dull color. C-18 semi-purified extracts displayed higher color saturation (smaller L* and larger C*ab) than crude extracts. The vibrant and broad color expression of fully-ripened fruit extract, especially after C-18 purification, suggests this North American native plant as a promising natural colorant source.

The brown marmorated stink bug, Halyomorpha halys (Stål), is an invasive pest from Asia that feeds on many agricultural crops in the United States, including blueberries. Yet, the effects of H. halys feeding on fruit chemistry and induced resistance to insects remain unknown. Here we hypothesized that frugivory by H. halys changes fruit chemical composition, which in turn affects insect feeding behavior. In field experiments, blueberry fruit was either mechanically injured or injured by 0 (control), 2, 5, or 10 H. halys Total soluble solids (°Brix) and anthocyanin and phenolic content in injured and uninjured fruits, as well as their effects on feeding behavior by conspecifics, were measured subsequently in the laboratory. Results showed lower °Brix values in injured fruit as compared with uninjured fruit. Fruit injured by 2 and 5 H. halys also had 32 and 20% higher total phenolics, respectively, than the uninjured controls. The proportions of the anthocyanins derived from delphinidin, cyanidin, and petunidin increased, whereas those from malvidin decreased, in fruit after mechanical wounding and frugivory by H. halys In dual-choice tests, H. halys fed more often on uninjured fruit than those previously injured by conspecifics. These results show that frugivory by H. halys reduces the amounts of soluble solids, alters anthocyanin ratios, and increases levels of phenolics, and, as a result, injured fruits were a less preferred food source for conspecifics. To our knowledge, this is the first study to investigate the effects of frugivory on fruit chemistry and induced fruit resistance against a fruit-eating herbivore.

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