Orbitides and free polyamines have similarly limited fungicidal activity against three common pathogens of flax in vitro

• Published in: Facets (Ottawa) Vol. 7; pp. 843 - 852
• Main Authors: Alves da Costa Ribeiro Quintans, Isadora Louise, Alves da Costa Ribeiro Souza, Juliana, Deyholos, Michael K
• Format: Journal Article
• Language: English
• Published: Canadian Science Publishing 09-06-2022
• Subjects: antifungal assay; CLPs; fungi; orbitides; phytopathogens; polyamines
• ISSN: 2371-1671; 2371-1671
• DOI: 10.1139/facets-2021-0201

Fusarium oxysporum f. sp. lini and Septoria linicola are causes of fusarium wilt and pasmo in flax ( Linum usitatissimum). Members of a third fungal genus, Alternaria spp., have also been found in fiber and linseed varieties of flax, and are a source of post-harvest spoilage and mycotoxins in a wide range of crops. We performed a microdilution assay and calculated the median effective concentration (EC
50
) to compare the potency of cyclolinopeptides (CLPs), two polyamines (spermidine and spermine), and the fungicide carbendazimin in the control of three fungi that have potential pathogenic activity ( F. oxysporum, S. linicola, and Alternaria spp), of which the first two are particulary significant causes of disease in flax. For carbendazim, all EC
50
values were <0.6 μg/mL. The observed EC
50
ranged from 111 to 340 μg/mL for a mixture of six unique CLPs, 109 to 778 μg/mL for spermine, and 21 to 272 μg/mL for spermidine. Spermidine was most effective against Alternaria sp., with an EC
50
of 21 μg/mL. The results presented here showed that polyamines and CLPs possess limited antifungal activities against several fungi, with spermidines the most effective naturally occurring compound tested. Our findings do not support the hypothesis that CLPs act as potent antifungals against the three species of pathogens tested.