Abstract
Bacterial wilt is a destructive disease caused by the phytopathogen Ralstonia solanacearum (R. solanacearum), which is widely found in various tobacco-growing areas all over the world. Botanical bactericidal substances have gradually emerged as a hot topic in modern pesticide research. In this study, the antibacterial activities of two phytochemicals (resveratrol and coumarin) against R. solanacearum and their in vivo and in vitro efficacy for controlling tobacco bacterial wilt were evaluated. We rule out significant biological effects of both phytochemicals using transmission electron microscope (TEM) and fluorescence microscope, which suppressed the growth of R. solanacearum. Furthermore, we demonstrated that the toxicity mechanisms mainly involved damaging bacterial cell membrane and preventing swarming motility and biofilm formation. A further pot experiment demonstrated that coumarin and resveratrol significantly inhibited early adhesion and colonization of R. solanacearum in tobacco plants and the corresponding control efficacies were 68% and 85% after incubation for 13 days, respectively. The findings of this study suggest that both resveratrol and coumarin have potential as non-toxic antimicrobial strategies for controlling tobacco bacterial wilt disease.
Highlights
Ralstonia solanacearum, belonging to the β-proteobacteria, is a soil-borne phytopathogenic bacterium that can cause bacterial wilt disease with destructive damage to a large number of economic crops, as well as some ornamentals
We demonstrated antibacterial activities of a series of coumarins series of coumarins against R. solanacearum with different substitution patterns, and the results against R. solanacearum with different substitution patterns, and the results found that hydroxylation found that hydroxylation at the C-6, C-7 or C-8 position significantly enhanced the antibacterial at the C-6, C-7 or C-8 position significantly enhanced the antibacterial activity of coumarins [31]
At a higher phytochemical concentration (128 μg/mL), it seems that the number of adherent bacterial cells was reduced even further, while green fluorescent material clustered and overlapped, with enhanced fluorescence. These results further demonstrated that both resveratrol and coumarin inhibited the formation of bacterial biofilms, in agreement with and resveratrol (Figure 7E,F) treatment at 64 μg/mL, only a few bacterial cells adhered to the carrier in a dispersed pattern; the green fluorescent material was markedly reduced and thinned compared with the control
Summary
Ralstonia solanacearum, belonging to the β-proteobacteria, is a soil-borne phytopathogenic bacterium that can cause bacterial wilt disease with destructive damage to a large number of economic crops, as well as some ornamentals. With the characteristic of genetic polymorphism in R. solanacearum, including worldwide geographic distribution and extraordinarily broad host range, bacterial wilt is one of the most devastating diseases in agriculture [1,2]. As a result of long-term co-evolution with the host and environment, R. solanacearum exhibits a high degree of complexity in its geographic distribution, host range, and pathogenetic mechanisms, making it difficult to prevent from infecting the host plants. Control measures against R. solanacearum have long relied on traditional chemical pesticides (e.g., zinc thiazole, bismerthiazol, and saisentong) and antibiotics in many countries. The use of these methods for field trial is largely limited due to their environmental pollution and potential health risks to human health or non-target organisms [3]
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