A functional analysis of mitochondrial respiratory chain cytochrome bc1 complex in Gaeumannomyces tritici by RNA silencing as a possible target of carabrone

The Effects of Antofine on the Morphological and Physiological Characteristics of Phytophthora capsici

Phytophthora capsici is an important plant pathogenic oomycete that causes great losses to vegetable production around the world. Antofine is an important alkaloid isolated from Cynanchum komarovii Al. Iljinski and exhibits significant antifungal activity. In this study, the effect of antofine on the mycelial growth, morphology, and physiological characteristics of P. capsici was investigated using colorimetry. Meanwhile, the activity of mitochondrial respiratory chain complexes of P. capsici was evaluated following treatment with a 30% effective concentration (EC30), as well as EC50 and EC70, of antofine for 0, 12, 24, and 48 h. The results showed that antofine had a significant inhibitory effect against P. capsici, with an EC50 of 5.0795 μg/mL. After treatment with antofine at EC50 and EC70, the mycelia were rough, less full, and had obvious depression; they had an irregular protrusion structure; and they had serious wrinkles. In P. capsici, oxalic acid and exopolysaccharide contents decreased significantly, while cell membrane permeability and glycerol content increased when treated with antofine. Reactive oxygen species (ROS) entered a burst state in P. capsici after incubation with antofine for 3 h, and fluorescence intensity was 2.43 times higher than that of the control. The activities of the mitochondrial respiratory chain complex II, III, I + III, II + III, V, and citrate synthase in P. capsici were significantly inhibited following treatment with antofine (EC50 and EC70) for 48 h compared to the control. This study revealed that antofine is likely to affect the pathways related to the energy metabolism of P. capsici and thus affect the activity of respiratory chain complexes. These results increase our understanding of the action mechanism of antofine against P. capsici.

Antifungal activity of Ligusticum chuanxiong essential oil and its active composition butylidenephthalide against Sclerotium rolfsii

BACKGROUND

Peanut stem rot caused by Sclerotium rolfsii is an epidemic disastrous soil-borne disease. Recently, natural products tend to be safe alternative antifungal agents to combat pathogens.

RESULTS

This work determined the preliminary antifungal activity of 29 essential oils against S. rolfsii and found that Ligusticum chuanxiong essential oil (LCEO) showed the best antifungal activity, with an EC50 value of 81.79 mg L-1 . Sixteen components (98.78%) were identified in LCEO by gas chromatography-mass spectrometry analysis, the majority by volume comprising five phthalides (93.14%). Among these five phthalides, butylidenephthalide was the most effective compound against S. rolfsii. Butylidenephthalide not only exhibited favorable in vitro antifungal activity against the mycelial growth, sclerotia production and germination of S. rolfsi, but also presented efficient in vivo efficacy in the control of peanut stem rot. Seven days after application in the glasshouse, the protective and curative efficacy of butylidenephthalide at 300 mg L-1 (52.02%, 44.88%) and LCEO at 1000 mg L-1 (49.60%, 44.29%) against S. rolfsii were similar to that of the reference fungicide polyoxin at 300 mg L-1 (54.61%, 48.28%). Butylidenephthalide also significantly decreased the oxalic acid and polygalacturonase content of S. rolfsii, suggesting a decreased infection ability on plants. Results of biochemical actions indicated that butylidenephthalide did not have any effect on the cell membrane integrity and permeability but significantly decreased nutrient contents, disrupted the mitochondrial membrane, inhibited energy metabolism and induced reactive oxygen species (ROS) accumulation of S. rolfsii.

CONCLUSION

Our results could provide an important reference for understanding the application potential and mechanisms of butylidenephthalide in the control of S. rolfsii. © 2023 Society of Chemical Industry.

Discovery of novel salicylaldehyde derivatives incorporating an α-methylene-γ-butyrolactone moiety as fungicidal agents

BACKGROUND

Plant diseases caused by phytopathogenic fungi and oomycetes pose a serious threat to ensuring crop yield and quality. Finding novel fungicidal candidates based on natural products is one of the critical methods for developing effective and environmentally friendly pesticides. In this study, a series of salicylaldehyde derivatives containing an α-methylene-γ-butyrolactone moiety were designed, synthesized, and their fungicidal activities were evaluated.

RESULTS

The bioassay studies indicated that compound C3 displayed an excellent in vitro activity against Rhizoctonia solani with a half-maximal effective concentration (EC50 ) value of 0.65 μg/mL, higher than that of pyraclostrobin (EC50  = 1.44 μg/mL) and comparable to that of carbendazim (EC50  = 0.33 μg/mL). For Valsa mali and Phytophthora capsici, compound C3 also showed good fungicidal activities with EC50 values of 0.91 and 1.33 μg/mL, respectively. In addition, compound C3 exhibited promising protective in vivo activity against R. solani (84.1%) at 100 μg/mL, which was better than that of pyraclostrobin (78.4%). The pot experiment displayed that compound C3 had 74.8% protective efficacy against R. solani at 200 μg/mL, which was comparable to that of validamycin (78.2%). The antifungal mode of action research indicated that compound C3 could change the mycelial morphology and ultrastructure, increase cell membrane permeability, affect respiratory metabolism by binding to complex III, and inhibit the germination and formation of sclerotia, thereby effectively controlling the disease.

CONCLUSION

The present study provides support for the application of these salicylaldehyde derivatives as promising potential pesticides with remarkable and broad-spectrum fungicidal activities against phytopathogenic fungi and oomycetes in crop protection. © 2023 Society of Chemical Industry.