Abstract
Botanical fungicides comprise attractive alternatives to chemical fungicides because of their environmental compatibility. Flavonoids extracted from Tagetes erecta L. have an inhibitory effect on fusarium wilt in watermelons caused by Fusarium oxysporum f. sp. niveum (FON). In this study, we synthesized one of these flavonoids, 2,5-dicyclopentylidene cyclopentanone (Tagetes erecta L. fungicide (TEF)) and assessed its activity against FON. In vitro, TEF inhibited FON growth and killed FON cells directly. TEF also affected FON cell physiology and mycelial structure. In watermelon plants with fusarium wilt, TEF protected the leaf cell structure and improved the germination rate of infected seeds while increasing overall plant resistance. A TEF-resistant mutant (FONM) was created by chemical mutagenesis. FON and FONM were analysed using iTRAQ and RNA-Seq, which identified 422 differentially expressed proteins and 7817 differentially expressed mRNAs in the proteome and transcriptome, respectively. The FONM mutations caused changes in the cell membrane and cell wall, which may constitute the site of action of TEF. Together, these results demonstrate that TEF could effectively control the watermelon fusarium wilt caused by FON, possibly through the inhibition of sterol biosynthesis. The data presented here suggest that TEF represents a new potential botanical anti-fungal drug.
Highlights
Fusarium wilt of watermelon is caused by Fusarium oxysporum f. sp. niveum (FON)
As currently widely used triazole fungicides can affect the formation of the fungal cell wall, resulting in cell changes including irregular swelling and considerable thickening[12], we concluded that TEF changes FON cell wall components
Bill et al.[21] used thyme oil obtained from avocado to treat the fungal infection anthracnose, and the results showed that the activities of Superoxide dismutase (SOD), POD, CAT, and pheynlalanin ammonialyase (PAL) all increased after treatment
Summary
Fusarium wilt of watermelon is caused by Fusarium oxysporum f. sp. niveum (FON). Worldwide, the loss of watermelons owing to FON infection has been increasing annually. As the process of breeding for FON-resistant cultivars can be challenging[1], chemical pesticides such as carbendazim, myclobutanil, and diniconazole have traditionally been used to control FON infections[2]. These drugs have high potential risks[3]. There have been no reports on the botanical fungicides to treat watermelon fusarium wilt caused by the FON pathogen. The extraction of these flavonoids directly from marigold roots for use on an agricultural scale was impractical To overcome this limitation, we have developed and patented a method to chemically synthesize the active substance (referred to as TEF; Patent No: ZL200810055370.X, China). The aim of the present study is to assess TEF’s antifungal effect on FON, its protective effect against fusarium wilt and the mechanism of action involved
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