Induction of systemic resistance in broad bean to rust using salicylic acid and two derivatives

Meerman, Johannes C (1992) Induction of systemic resistance in broad bean to rust using salicylic acid and two derivatives. MSc(R) thesis, University of Glasgow.

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Investigations were made on the induction of systemic resistance (SR) to rust (Uromyces viciae-fabae) infection in broad bean (Vida faba), using exogenous inducers. In vivo and in vitro experiments were carried out in order to study various aspects of the systemic induced resistance (SIR). In addition, studies on the possible involvement of endogenous salicylic acid (Sa) in SIR were initiated. Thus, in broad bean, SR to rust infection could be induced using Sa, acetylsalicylic acid (AcSa), and sodium salicylate (NaSa). SIR was expressed as a reduction in the number of pustules cm-2 of the challenge-inoculated leaf. Increasing the interval between treatment of the first leaves with Sa, NaSa, or AcSa and inoculation of the third leaves had little effect on SIR to rust infection in broad bean. Sa, or a signal(s) produced after treatment with salicylates moved both acropetally and basipetally in broad bean plants, although the protection was greater in leaves above the induced leaves than below the induced leaves. A lag-period of at least 28 h after induction with Sa, NaSa, or AcSa was required before SR was expressed in broad bean. It is clear that the treated leaves were essential for SR to be induced, in the upper or lower leaves. Sa did not have a direct antifungal effect on broad bean rust, although NaSa and AcSa appeared to affect the rust directly. High concentrations of Sa, NaSa, and AcSa caused damage to the sprayed leaves, although the toxicity to plant tissue is unlikely to have caused the observed decrease in rust infection by Sa-, NaSa-, or AcSa treatments in experiments examining SIR. The effect of the salicylates on in vitro fungal growth was dependent on the particular fungus used (Botrytis cinerea or Pyrenophora avenae) and also on the pH of the medium. Growth reductions caused be the salicylates in these fungi appeared the be the result of the low pH of the medium. However, it seems unlikely that the reduction in rust infection in upper or lower leaves, caused by salicylate-treatment of lower or upper leaves respectively, was due to a direct effect of these compounds on the fungus. The variability between experiments observed in this work may reflect differences in environmental conditions, natural variability in broad bean (which is notoriously variable) or metabolism and/or conjugation of the salicylates. Salicylic acid in plant tissue could not be determined using TLC followed by spectrophotometry or spectrofluorometry. Using these procedures it seems likely that Sa- conjugates and/or other phenolic compounds were also being detected.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Keywords: Plant pathology.
Colleges/Schools: College of Medical Veterinary and Life Sciences
Supervisor's Name: Walters, Dr. Dale
Date of Award: 1992
Depositing User: Enlighten Team
Unique ID: glathesis:1992-72409
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:12
Last Modified: 22 Jul 2021 10:00

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