Anti-Fungal Activity of Moutan cortex Extracts against Rice Sheath Blight (Rhizoctonia solani) and Its Action on the Pathogen’s Cell Membrane

Abstract

Rice sheath blight (RSB) caused by Rhizoctonia solani is one of the most destructive diseases of rice (Oryza sativa). Although chemical fungicides are the most important control methods, their long-term unreasonable application has brought about problems such as environmental pollution, food risks, and non-target poisoning. Therefore, considering the extraction of fungistatic substances from plants may be an alternative in the future. In this study, we found that the Moutan cortex ethanol extract has excellent antifungal activity against R. solani, with a 100% inhibition rate at 1000 μg/mL, which aroused our great exploration interest. In-depth exploration found that the antifungal active ingredients of M. cortex were mainly concentrated in the petroleum ether extract of the M. cortex ethanol extract, which still maintained a 100% inhibition rate with 250 μg/mL, and its effective medium concentration (EC 50 ) was 145.33 μg/mL against R. solani. Through the measurement of extracellular relative conductivity and OD 260 , the petroleum ether extract induced leakage of intracellular electrolytes and nucleic acids, indicating that the cell membrane was ruined. Therefore, we preliminarily determined that the cell membrane may be the target of the petroleum ether extract. Moreover, we found that petroleum ether extract reduced the content of ergosterol, a component of the cell membrane, which may be one of the reasons for the cell membrane destruction. Furthermore, the increase of MDA content would lead to membrane lipid peroxidation, further aggravating membrane damage, resulting in increased membrane permeability. Also, the destruction of the cell membrane was observed by the phenomenon of the mycelium being transparent and broken. In conclusion, this is the first report of the M. cortex petroleum ether extract exhibiting excellent antifungal activity against R. solani. The effect of the M. cortex petroleum ether extract on R. solani may be on the cell membrane, inducing the disorder of intracellular substances and metabolism, which may be one of the antifungal mechanisms against R. solani.

Antifungal Activity and Action Mechanisms of 2,4-Di-tert-butylphenol against Ustilaginoidea virens

“…The fungal cell wall is a dynamic skeleton with high plasticity that protects the cell from different stresses . It has been reported that some natural antifungal compounds that damage the cell membrane could target the cell wall at the same time . To explore the effects of 2,4-DTBP on the cell wall integrity of U.…”

“…22 It has been reported that some natural antifungal compounds that damage the cell membrane could target the cell wall at the same time. 23 To explore the effects of 2,4-DTBP on the cell wall integrity of U. virens, mycelia were stained with CFW, which is a specific fluorescent dye that could bind to chitin at the fungal cell wall and emit blue fluorescence. 24 As shown in Figure 6, all of the mycelia exhibited blue fluorescence.…”

Inhibitory Activity Against Rhizoctonia Solani and Chemical Composition of Extract from Moutan Cortex

“…The method of petroleum ether extract preparation of MC was by the cold-soaking method. [21] MC was crushed and sieved using a 60 mesh sieve. Next, it was weighed to 30 g and dissolved in 300 mL of petroleum ether at room temperature.…”

“…Additional extraction work demonstrated that the active component was primarily present in the petroleum ether extract. [21] However, the chemical components of MC petroleum ether extract that exert the main antifungal activity are unclear.…”

Novel Pyrazole-4-Carboxamide Derivatives Containing Oxime Ether Group as Potential SDHIs to Control Rhizoctonia solani

“…Due to the expanding population and growing food demands, rice ( Oryza sativa L.), one of the most widely consumed cereal crops in the world, is of great importance to feed the increasing population. , Rhizoctonia solani is a highly detrimental fungus to rice crops, with the potential to cause rice sheath blight (ShB) and result in significant reductions in both the yield and quality of rice. − For instance, this fungi results in significant yield losses of rice up to 50% in some South Asian countries such as China and India. , Up to date, chemical fungicides remain the most efficient and dependable means for controlling R. solani.…”