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Previously, we reported that marine yeast Scheffersomyces spartinae exhibited biocontrol efficacy against the gray mold of strawberries caused by Botrytis cinerea. Herein, tryptophol, a quorum-sensing molecule, was identified in the metabolites of S. spartinae. Subsequently, we found that 25 µM tryptophol promoted population density, biofilm formation, and cell aggregation of S. spartinae. Furthermore, 25 µM tryptophol improved the biocontrol efficacy of S. spartinae against B. cinerea in vitro and in the strawberry fruit. Under a scanning electronic microscope, tryptophol facilitated colonization and biofilm formation on strawberry wounds, showing that tryptophol increased the biocontrol efficacy of S. spartinae via quorum sensing. Transcriptome analysis revealed that tryptophol upregulated the gene expression of SDS3, DAL81, DSE1, SNF5, SUN41, FLO8, and HOP1, which was associated with cell adhesion or biofilm formation. Thus, to the best of our knowledge, this study was the first to report that tryptophol improved the biocontrol efficacy of S. spartinae via quorum sensing.

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This study aims to evaluate the antifungal effects of volatile organic compounds (VOCs) produced by a marine biocontrol yeast, Scheffersomyces spartinae W9. The results showed that the VOCs from the yeast inhibited the growth of Botrytis cinerea mycelium and spore germination by 77.8% and 58.3%, respectively. Additionally, it reduced the disease incidence and lesion diameter of gray mold on the strawberry fruit surface by 20.7% and 67.4%, respectively. Electronic micrographs showed that VOCs caused damage to the morphology and ultrastructure of the hyphae. Based on headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS), S. spartinae W9 emitted 18 main VOCs, and the pure substance of VOCs, such as 3-methyl-1-butanol, 2-methyl-1-butanol, 2-phenylethanol, and isoamyl acetate, showed antifungal effects against B. cinerea mycelium growth. Among them, 2-phenylethanol exhibited the strongest antifungal activity. It has been concluded that VOCs are the key antifungal mechanism of S. spartinae W9, and a promising strategy for controlling gray mold on strawberry fruit.

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The marine yeast Scheffersomyeces spartinae W9 is a promising biocontrol agent for gray mold caused by Botrytis cinerea in strawberries. Improving the biocontrol efficacy of S. spartinae W9 is necessary for its commercial application. In this study, different concentrations of ß-glucan were added to the culture medium to evaluate its effect on the biocontrol efficacy of S. spartinae W9. The results showed that 0.1% ß-glucan could increase the biocontrol effect of S. spartinae W9 against B. cinerea in strawberries and in vitro. We found that adding 0.1% ß-glucan to the culture medium promoted the growth of S. spartinae W9 in wounds of strawberries, enhanced biofilm formation ability, and secreted more ß-1,3-glucanase. In addition, 0.1% ß-glucan increased the survival rate of S. spartinae W9 under oxidative, thermal, osmotic, and plasma membrane stressors. Transcriptome analysis revealed 188 differential expressed genes in S. spartinae W9 cultured with or without 0.1% ß-glucan, including 120 upregulated and 68 downregulated genes. The upregulated genes were associated with stress response, cell wall formation, energy production, growth, and reproduction. Thus, culturing with 0.1% ß-glucan is an effective way to improve the biocontrol ability of S. spartinae W9 against gray mold in strawberries.

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2-Phenylethanol (2-PE), a common compound found in plants and microorganisms, exhibits broad-spectrum antifungal activity. Using Botrytis cinerea, we demonstrated that 2-PE suppressed mycelium growth in vitro and in strawberry fruit and reduced natural disease without adverse effects to fruit quality. 2-PE caused structural damage to mycelia, as shown by scanning and transmission electron microscopy. From RNA sequencing analysis we found significantly upregulated genes for enzymatic and nonenzymatic reactive oxygen species (ROS) scavenging systems including sulfur metabolism and glutathione metabolism, indicating that ROS stress was induced by 2-PE. This was consistent with results from assays demonstrating an increase ROS and hydrogen peroxide levels, antioxidant enzyme activities, and malondialdehyde content in treated cells. The upregulation of ATP-binding cassette transporter genes, the downregulation of major facilitator superfamily transporters genes, and the downregulation of ergosterol biosynthesis genes indicated a severe disruption of cell membrane structure and function. This was consistent with results from assays demonstrating compromised membrane integrity and lipid peroxidation. To summarize, 2-PE exposure suppressed B. cinerea growth through ROS stress and cell membrane disruption.

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Chinese bayberry fruit were treated with hot air (HA) at 48 ℃ for 3 h and then stored at 4 ℃ for 15 d. Changes in fungal communities were analyzed by high-throughput sequencing (HTS), and decay and fruit quality were monitored during storage. The results showed that HA treatment effectively maintains fruit quality and the richness and diversity of fungal communities. Heat treatment inhibited decay development and reduced the growth of fungi in the genera Botryotinia spp., Davidiella spp., Hanseniaspora spp., and Candida spp. Canonical correspondence analysis further revealed that Botryotinia spp. and Davidiella spp. were positively correlated with fruit decay and weight loss. FUNGuild analysis demonstrated that HA-treated bayberries had a lower relative abundance within the plant pathogen guild, but higher relative abundance within the endophyte guild. The results suggest that HA treatment reduces pathogens by favoring the increase of endophytes, providing new insight into the decay development and quality changes during the storage of postharvest Chinese bayberries.

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This study aimed to reveal the effects and possible mechanism of terpinen-4-ol, the main component of tea tree oil (TTO), on the disease resistance of strawberry fruit. When the effects of TTO and its components were compared on the decay development in fruit inoculated with Botrytis cinerea after treatment, strawberry treated with terpinen-4-ol showed the lowest disease incidence (44.4%) after 48 h and also the smallest lesion diameter during the whole storage. This indicates that terpinen-4-ol induces the highest disease resistance in strawberry compared with TTO and other components. Untargeted metabolomic analysis showed that terpinen-4-ol treatment strongly activated phenylpropanoid biosynthesis and flavonoid metabolism pathway by increasing the accumulation of cinnamaldehyde, coniferyl aldehyde, naringenin, taxifolin, quercetin, and quercitrin in fruit at 12 h after treatment. In addition, terpinen-4-ol treatment also caused the accumulation of total phenolics and lignin by enhancing activities and relative gene expression of key enzymes in the phenylpropanoid metabolism pathway. These results suggest that terpinen-4-ol, as the key component of TTO, is the most important contributor to the effectiveness of TTO in improving disease resistance of strawberry fruit through activating the phenylpropanoid metabolism pathway.

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This study investigated the effects of heat treatment (hot air at 38 degrees C) and antagonistic yeast (Pichia guilliermondii) alone or in combination against postharvest diseases (Botrytis cinerea, Alternaria alternata and Rhizopus nigricans) on cherry tomato fruit, and evaluated the elicitation of active defense responses. Results showed that heat treatment at 38 degrees C for 24 h in combination with P. guilliermondii at 1 x 10(8) CFU mL(-1) was the most effective approach to reduce various infections on cherry tomato fruit's wounds. Moreover, the combined heat and P. guilliermondii treatment stimulated a rapid increase of H(2)O(2) and higher lignin deposition in cherry tomato fruit showing that the oxidative burst and biological synthesis of lignin might play important roles in the fruit's active defense responses. In addition, the reduction of the fruit's susceptibility to pathogens by the combined treatment was positively correlated with higher activities of phenylalanine ammonia-lyase (PAL) and beta-1,3-glucanase in cherry tomato fruits, both of which are associated with plant defense responses.

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