Abstract
The current study aimed to examine the in vitro and in vivo antifungal potential of pinocembrin-7-glucoside (P7G). P7G is an antifungal flavanone glycoside isolated from Ficus hirta Vahl. fruit against Penicillium italicum, a causative pathogen of blue mold disease in citrus fruit, and this study elucidates its possible action mechanism. P7G had a prominent mycelial growth inhibitory activity against P. italicum, with an observed half maximal effective concentration, minimum inhibitory concentration and minimum fungicidal concentration of 0.08, 0.2, and 0.8 g/L, respectively. The data from the in vivo test show that P7G significantly reduced blue mold symptoms and disease development of P. italicum in artificially inoculated “Newhall” navel orange. Compared to the control, increases in the cell membrane permeability of P. italicum supernatant and decreases in the intracellular constituent (e.g., soluble protein, reducing sugar, and total lipid) contents of P. italicum mycelia were identified, supporting scanning electron microscopy and transmission electron microscopy observations. Furthermore, a marked decline in both chitin and glucanase contents of P. italicum mycelia treated with P7G was induced by increasing its related degrading enzyme activities, suggesting that the cell wall structure was destroyed. The current study indicated that P7G may be a novel alternative for reducing blue mold by suppressing mycelial growth of P. italicum via a cell membrane/wall-targeting mechanism.
Highlights
By far, China is the largest country in the world in terms of both citrus yield and cultivated area, and it has a large variety of species and varieties, such as loose-skin mandarin, sweet orange, pummelo, kumquat, lemon, grapefruit, citron, and different special hybrids [1,2]
With the highest Minimal Inhibitory Concentration (MIC) and minimum fungicidal concentration (MFC) value (0.8 g/L). These results are in line with our previous study of clove essential oil (CEO) [35], and indicating that the in vitro antifungal efficiency of CEO may be similar and better than traditional citrus preservatives, with the values of MIC against P. italicum, P. digitatum, G. citri-aurantii, and A. citri ranging from 0.2 to 1.0 mL/L
In the in vitro study, our results demonstrated that, in comparison with the control group, the colony diameter of P. italicum dropped to 50% when P7G achieved 0.08 g/L on PDA; the germination rate of P. italicum spore was suppressed by half in 0.032 g/L P7G in potato dextrose broth (PDB), indicating that in comparison to mycelia, the spore germination of P. italicum was more sensitive to P7G treatment (Figure 2 and Table 2)
Summary
China is the largest country in the world in terms of both citrus yield and cultivated area, and it has a large variety of species and varieties, such as loose-skin mandarin, sweet orange, pummelo, kumquat, lemon, grapefruit, citron, and different special hybrids [1,2]. Blue mold is the primary postharvest disease that causes 20–50% of citrus fruit loss in. Increasing public concerns regarding chemical residues on human health, environmental pollution, and resistance pathogens due to excessive use of chemical fungicides have initiated an investigation. Microorganisms 2020, 8, 536 residues on human health, environmental pollution, and resistance pathogens due to excessive use of chemical fungicides have initiated an investigation into alternative strategies for reducing postharvest fungal decay for without anypostharvest human, environmental, plant toxicity [11,12,13]. A into alternative strategies reducing fungal decayor without any human, environmental, huge number studies have adocumented antifungal effects of plant-derived or plant toxicity of Recently, huge numberthe of studies have documented the antifungalnatural effects compounds, generally regarded as safe (GRAS)
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