Foliar-applied ethephon enhances the content of anthocyanin of black carrot roots (Daucus carota ssp. sativus var. atrorubens Alef.)

Abstract

BackgroundBlack carrots (Daucus carota ssp. sativus var. atrorubens Alef.) constitute a valuable source of anthocyanins, which are used as natural red, blue and purple food colourants. Anthocyanins and phenolic compounds are specialised metabolites, accumulation of which often requires elicitors, which act as molecular signals in plant stress responses. In the present study, ethephon, an ethylene-generating compound was explored as enhancer of anthocyanin and phenolic contents during growth of ‘Deep Purple’ black carrots. The effects of ethephon on several parameters were investigated, and the expression of biosynthetic anthocyanin genes was studied during growth and anthocyanin accumulation.ResultsRoots of ethephon-treated carrot plants exhibited an increase in anthocyanin content of approximately 25%, with values ranging from 2.25 to 3.10 mg g−1 fresh weight, compared with values ranging from 1.50 to 1.90 mg g−1 fresh weight in untreated roots. The most rapid accumulation rate for anthocyanins, phenolic compounds, soluble solids and dry matter was observed between 10 and 13 weeks after sowing in both untreated and ethephon-treated carrots. The differences in anthocyanin contents between untreated and treated carrots increased for several weeks after the ethephon treatment was terminated. Five cyanidin-based anthocyanin forms were identified, with variable relative abundance values detected during root growth. Overall, the expression of the anthocyanin biosynthetic genes analysed (PAL1, PAL3, F3H1, DFR1, LDOX2) increased in response to ethephon treatment, as did the expression of the MYB1 transcription factor, which is associated with activation of the phenylpropanoid pathway under stress conditions. In addition, a correlation was proposed between ethylene and sugar contents and the induction of anthocyanin synthesis.ConclusionsThis study presents a novel method for enhancing anthocyanin content in black carrots. This finding is of economic importance as increased pigment concentration per unit of biomass implies improved profitability parameters in food colour production. We provide new insight into the accumulation patterns of the different cyanidin-based anthocyanins and phenolic compounds during root growth. Moreover, we show that enhanced anthocyanin content in ethephon-treated carrots is accompanied by increased expression of anthocyanin biosynthetic genes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-017-1021-7) contains supplementary material, which is available to authorized users.

Determination of Anthocyanins of Purple Carrot Two Cultivars

“…The chromatograms of anthocyanins of the two cultivars of purple carrot extracts under investigation in a current paper are almost the same but different from published elsewhere [5][6][7][8][9][10] The shift may be the consequence of cyanidin derivatives acylation with substituted cinnamic acids, the proposition is confirmed by appearance of local maxima at 330 nm. These maxima of absorption reveal the presence in the anthocyanins' structure substituted cinnamic acids chromophore groups [12].…”

“…Among the plants that are used nowadays for production of anthocyanin colorants there are purple (or even black) colored carrot roots [5][6][7][8][9][10]. However, in Russia, this type of carrots was still out of interest, and only recently, seeds of some purple-colored carrots became available in the market for the gardeners, though we could not find information about type of anthocyanins and overall anthocyanin accumulation in the roots of the carrots.…”

UV-B Exposure of Black Carrot (Daucus carota ssp. sativus var. atrorubens) Plants Promotes Growth, Accumulation of Anthocyanin, and Phenolic Compounds

“…sativus var. atroburens), with anthocyanins as major secondary metabolites [1]. The main interest in black carrot anthocyanins is related to their high ratio of mono-acylated structures with three sugar moieties, which provide a high physicochemical stability to the colour extracts and make black carrot suitable for developing natural colourants (labelled E163 in Europe) [2].…”

Combined Effects of Water Deficit, Exogenous Ethylene Application and Root Symbioses on Trigonelline and ABA Accumulation in Fenugreek

“…Ethephon treatment increased the accumulation of proline and antioxidant enzymes activity in maize subjected to water stress by maintaining water status, membrane stability and modulate cuticular wax biosynthesis [35]. In addition, foliar-applied ethephon markedly improve anthocyanin and total phenolic content in black carrots [36]. Several lines of evidence indicated the stimulating effect of ethylene on diosgenin content and enzyme activities also in fenugreek [37,38].…”