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Screening of organically based fungicides for apple scab (Venturia inaequalis) control and a histopathological study of the mode of action of a resistance inducer

Bengtsson, M.; Jørgensen, H.J.L.; Pham, A.; Wulff, E. and Hockenhull, J. (2005) Screening of organically based fungicides for apple scab (Venturia inaequalis) control and a histopathological study of the mode of action of a resistance inducer. Poster at: 7th International IOBC/wprs Workshop on Orchard Diseases, Piacenza, Italy, 31 August - 4 September 2005.

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A range of possible substitutes for copper-based fungicides for control of apple scab (Venturia inaequalis) in organic growing were tested in laboratory and growth chamber experiments in the Danish project StopScab (2002-2004). Eighteen crude plant extracts, 19 commercial plant-based products and 6 miscellaneous compounds were tested for their ability to reduce scab symptoms on apple seedlings. Most of the compounds were also tested for their effect on conidium germination on glass slides. Fourteen of the crude plant extracts, 13 of the commercial plant products and 5 of the miscellaneous compounds showed promising control efficacies when used either preventively or curatively in the plant assay. A histopathological study was carried out on the mode of action of the resistance inducer, acibenzolar-S-methyl (ASM), which reduced scab severity and sporulation on apple seedlings in several plant assays when applied as preventive treatment. The effect of the inducer on key pre- and post-penetration events of V. inaequalis was studied and compared to these events in water-treated control leaves. The histopathological study showed that the inducer had its strongest effect on post-penetration events indicated by delayed infection and reduced stroma development. In addition, a small but significant inhibition of conidial germination and a stimulation of germ tube length were observed. This investigation provides new histopathological evidence for the mode of action of ASM against V. inaequalis and serves as a model for evaluation of the mechanisms by which the organically based fungicides reduce infection of V. inaequalis.

EPrint Type:Conference paper, poster, etc.
Type of presentation:Poster
Keywords:apple scab, control, botanical fungicides, induced resistance, organic growing, plant extracts, histopathological study, screening
Subjects: Crop husbandry > Crop health, quality, protection
Research affiliation: Denmark > DARCOF II (2000-2005) > I.14 (StopScab) Control of scab in organic apple growing
Denmark > KU - University of Copenhagen > KU-LIFE - Faculty of Life Sciences
Deposited By: Bengtsson, Post doc Marianne Vibeke
ID Code:9988
Deposited On:17 Nov 2006
Last Modified:25 Jun 2014 08:19
Document Language:English
Refereed:Not peer-reviewed

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