The efficacy of 8-hydroxyquinoline derivatives in controlling the fungus Ilyonectria liriodendri, the causative agent of black foot disease in grapevines

In vitro evaluation of the efficacy of 8-hydroxyquinoline derivatives for the control of Phaeomoniella chlamydospora, the causative agent of Petri disease in grapevines

AIM

This study evaluates the in vitro efficacy of 8-hydroxyquinoline (8HQ) derivatives in controlling the phytopathogenic fungus Phaeomoniella chlamydospora.

METHODS AND RESULTS

The in vitro tests assessed the susceptibility to the minimum inhibitory concentration (MIC), checkerboard assay, mycelial growth (MG) inhibition, and EC50 determination. Among the seven agricultural fungicides tested, tebuconazole (TEB) displayed the lowest MIC, 1.01 µg mL-1, followed by captan (CAP), thiophanate methyl (TM), and mancozeb with MICs of 4.06, 5.46, and 10.62 µg mL-1, respectively. The 8HQ derivatives used in this study were clioquinol and PH 151 (PH) with MICs of 1.09 and 2.02 µg mL-1, respectively. PH associated with TEB and CAP showed synergism and inhibited 95.8% of MG at the highest dose. TEB inhibited 100% of MG at the three highest doses, while associated with PH exhibited the lowest EC50 (0.863 + 0.0381 µg mL-1).

CONCLUSIONS

We concluded that the 8HQ derivatives tested controlled effectively the P. chlamydospora in vitro. PH associated with CAP and TEB exhibited a synergistic effect. The association between PH and TM was considered indifferent.

IMPACT STATEMENT

This study expands the list of active ingredients tested against P. chlamydospora, with the PH 151 and clioquinol derivatives being tested for the first time. The in vitro efficacy and synergistic action with other fungicides suggest a potential use as a grapevine wound protectant. This association makes it possible to reduce doses and increase the potency of both drugs, reducing the risk of resistance development and harm to humans and the environment.

Biological and chemical control of Ectophoma multirostrata causing root-rot and seedling death of Celosia argentea in Karbala/Iraq

This study was conducted in the College of the Agriculture/University of Karbala to control the fungus Ectophoma multirostrata that causes root rot of Celosia argentea by using Azotobacter chrocooccum, Salicylic acid and the chemical pesticide Beltanol. The pathogenic E. multirostrata was isolated for the first time in Iraq and showed a reduction in seed germination by 16.66% and 16.00%. The results showed that the bio-control bacteria A. chrocooccum, Salicylic acid and Beltanol effectively reduced the infection rate and severity of Celosia argentea root rot disease and increased the growth parameters. Among the treatments, Beltanol was the highest in reducing the infection rate and severity down to 0.00%, followed by the treatment of integration between A. chrocooccum and Salicylic acid to minimize infection and severity to 16.33% and 8.00%, compared to the infected untreated that showed 80%, 62.00% respectively. In addition, the A. chrocooccum and Salicylic acid integration improved plant growth, including shoot length, shoot and root dry weight to be 22.50 cm, 0.423 g and 0.133 g, compared to the untreated infected treatment that resulted in 5.00 cm, 0.090 g, and 0.003g, respectively. Keywords: Celosia argentea, Ectophoma multirostrata, Azotobacter chrocooccum, Root rot

Clioquinol and 8-hydroxyquinoline-5-sulfonamide derivatives damage the cell wall of Pythium insidiosum

AIMS

To evaluate the antimicrobial activity and to determine the pharmacodynamic characteristics of three 8-hydroxyquinoline derivatives (8-HQs) against Pythium insidiosum, the causative agent of pythiosis.

METHODS AND RESULTS

Antimicrobial activity was tested by broth microdilution and MTT assays. The antimicrobial mode of action was investigated using sorbitol protection assay, ergosterol binding assay, and scanning electron microscopy. Clioquinol, PH151, and PH153 were active against all isolates, with MIC values ranging from 0.25 to 2 µg ml-1. They also showed a time- and dose-dependent antimicrobial effect, damaging the P. insidiosum cell wall.

CONCLUSIONS

Together, these results reinforce the potential of 8-HQs for developing new drugs to treat pythiosis.