Abstract Fusarium Head Blight (FHB) is one of the most important diseases affecting wheat production. The disease causes yield and quality losses and hinders commercialization because of frequent grain contamination with trichothecenes, sesquiterpene mycotoxins that are harmful to human and animals and act as pathogenicity factors for FHB. Although not always effective, application of fungicides is the most common method for FHB management; thus, there is an urgent need to develop new efficient and sustainable tools. We analyzed the inhibitory activity of a group of commercially available naturally occurring compounds on the production of trichothecenes and on the severity of FHB on field-grown wheat spikes inoculated with Fusarium graminearum. The gene TRI5 codifies trichodiene synthase, the enzyme that catalyzes the synthesis of trichodiene, a volatile intermediate to trichothecenes. Our first aim was to obtain a trichothecene non-producing mutant of the pathogen by gene disruption of this gene. Seventeen putative ΔTRI5 mutants produced in the laboratory were characterized for pathogenicity and trichothecene production. The target gene was correctly and efficiently replaced in more than 75% of the transformants obtained, indicating a high efficacy of the approach used for gene disruption. Selected commercially available natural inhibitors -eugenol, apocynin, caffeic acid and propyl gallate-, were used to test their effect on trichodiene production in vitro and in field-grown wheat spikes inoculated with F. graminearum, using a ΔTRI5 mutant as non-trichodiene production control. Fungal volatile organic compounds production was measured by gas chromatography coupled to mass spectrometry. Caffeic acid, apocynin and eugenol produced a significant reduction of trichodiene production in vitro. In field assays, sesquiterpene inhibition was also significant at 2 days post inoculation (dpi), showing that effective inhibition of the trichothecene precursor can be achieved through the action of commercially available naturally occurring compounds. However, at later stages (>7 dpi) the production of trichodiene was similar to that of the F. graminearum-inoculated control. At 21 dpi, FHB severity did not differ between the treatments with inhibitors and the inoculated control. Hence, further experiments are required to identify the most appropriate inhibitors concentrations and formulations to improve their bioavailability and to achieve long lasting protection against F. graminearum infections.

中文翻译：

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禾谷镰刀菌中单端孢霉烯生产的市售天然抑制剂：控制小麦赤霉病的策略

摘要 镰刀菌赤霉病（FHB）是影响小麦生产的重要病害之一。由于单端孢霉烯、倍半萜类真菌毒素对人类和动物有害并作为 FHB 的致病因素，这种疾病会导致产量和质量损失并阻碍商业化。虽然并不总是有效，但使用杀菌剂是 FHB 管理最常用的方法；因此，迫切需要开发新的高效和可持续的工具。我们分析了一组市售天然化合物对单端孢霉烯的产生和 FHB 对接种禾谷镰刀菌的田间小麦穗的抑制活性。TRI5 基因编码单丁二烯合酶，​​催化单丁二烯合成的酶，单端孢霉烯的挥发性中间体。我们的第一个目标是通过对该基因的基因破坏来获得病原体的单端孢霉烯非生产突变体。实验室产生的 17 个推定的 ΔTRI5 突变体被表征为致病性和单端孢霉烯的产生。在获得的转化体中，75% 以上的靶基因被正确有效地替换，表明该方法用于基因破坏的效率很高。选定的市售天然抑制剂 - 丁香酚、夹竹桃素、咖啡酸和没食子酸丙酯 - 用于在体外和在接种禾谷镰刀菌的田间小麦穗中测试它们对单色二烯生产的影响，使用 ΔTRI5 突变体作为非单色二烯生产控制。真菌挥发性有机化合物的产生通过与质谱联用的气相色谱法进行测量。咖啡酸、夹竹桃素和丁子香酚在体外显着减少了单孢菌素的产生。在田间测定中，倍半萜烯抑制在接种后 2 天 (dpi) 也很显着，表明可以通过市售天然化合物的作用实现对单端孢霉烯前体的有效抑制。然而，在后期（> 7 dpi），单菌二烯的产量与接种禾谷镰刀菌的对照相似。在 21 dpi，FHB 严重程度在抑制剂处理和接种对照之间没有差异。因此，