Comparative studies on the effects of a yucca extract and acibenzolar-S-methyl (ASM) on inhibition of Venturia inaequalis in apple leaves

Marianne Vibeke Bengtsson, Ednar Gadelha Wulff, Hans Jørgen Lyngs Jørgensen, Thi Hue Anh Pham, Mette Lübeck, John Hockenhull

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    Abstract

    The effect of an extract of Yucca schidigera on the control and infection process of the apple scab pathogen, Venturia inaequalis, was examined and compared with the chemical resistance inducer, acibenzolar-S-methyl (ASM). In seedling assays, both materials significantly reduced apple scab symptoms and pathogen sporulation on leaves and both showed similar control efficacies as the reference treatment, sulphur. Whereas yucca extract and sulphur gave significant inhibition of conidial germination in vitro, ASM did not inhibit germination. Histopathological studies of the infection process of V. inaequalis in apple leaves showed that the yucca extract primarily acted by inhibiting pre-penetration events and penetration itself. In contrast, the ASM treatment significantly inhibited more stages of the infection process (pre-penetration, penetration and post-penetration events). These observations suggest that the yucca extract acted mainly by a direct fungitoxic effect whereas ASM, as expected, acted as a resistance inducer. However, expression studies of two genes encoding the PR proteins, PR1 and PR8, in apple seedlings indicated that yucca extract may also affect plant defence as expression of both genes was up-regulated following yucca treatment, to a level similar to that observed after treatment with ASM. The fungitoxic effect of sulphur on V. inaequalis was also confirmed in this study.
    Original languageEnglish
    JournalEuropean Journal of Plant Pathology
    Volume124
    Issue number2
    Pages (from-to)187-198
    Number of pages12
    ISSN0929-1873
    DOIs
    Publication statusPublished - 2009

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