Control of fungal plant pathogens using novel putrescine analogues

Havis, Neil D (1993) Control of fungal plant pathogens using novel putrescine analogues. PhD thesis, University of Glasgow.

Abstract

The effects of a number of synthetic, novel putrescine analogues were examined on a range of fungal pathogens both in vivo and in vitro. The three major compounds studied were E-1,4-Diaminobut-2-ene (E-BED), E-N,N,N',N'-Tetraethyl-1,4-diaminobut-2-ene (TED-1) and 1,2-bis(aminomethyl)-4,5 dimethylcyclohexa-1,4-diene (BAD). Each of these compounds gave significant control of Erysiphe graminis f.sp. hordei Marchal infection of barley seedlings. Post-inoculation treatments with these compounds were more effective than pre-inoculation treatments, which may be related to a perturbation of polyamine biosynthesis in the germinating conidia on the leaf surface. These three compounds all exhibited xylem mobility within the barley plant and E-BED and TED-1 appeared to possess some phloem mobility. The fate of these compounds within plants is still unclear however. The effects of various salts and derivatives of these three compounds on Erysiphe graminis infection of barley seedlings were also examined. These novel compounds gave slightly less control of Erysiphe graminis infection than active ingredients used in commercially available fungicides, when compared in the glasshouse environment. This may be due to the higher concentrations and superior formulations of the active ingredients used. In a field scale comparison, E-BED gave good early season control of E. graminis infection of barley. This control was comparable to that achieved with the commercial standard used and was superior to that produced by the ornithine decarboxylase (ODC) inhibitor, difluoromethylornithine (DFMO). E-BED also produced significant increases in plant height, plant dry weight and grain weight. Mixtures of these novel compounds gave greater control of E. graminis infection than sprays of the compounds alone. These three compounds produced very different effects on other fungal pathogens in vivo. Both E-BED and TED-1 gave significant control of Uromyces viciae-fabae and Botrytis fabae infection of broad bean seedlings. In contrast, BAD gave no control of U. viciae-fabae and only poor control of B. fabae infection. E-BED and TED-1 gave significant control of Phytophthora infestans infection of potato leaf discs. However,BAD gave poor control of this pathogen. All of these compounds gave significant control of Podosphaera leucotricha infection of apple seedlings. The compounds were also tested against a range of fungal pathogens in vitro. This was achieved by supplementing either solid or liquid growth media with the compounds. E-BED reduced growth of Botrytis cinerea significantly and was the only compound to reduce growth of the rice blast fungus, Pyricularia oryzae, even though this control was poor. E-BED and TED-1 both gave significant reductions in the growth of the oat leaf stripe pathogen, Pyrenophora avenae. The effect of E-BED and TED-1 on polyamine levels and poly amine biosynthetic enzymes in P. avenae was examined. E-BED depleted enzyme activities yet produced a very substantial increase in putrescine levels in the fungus. Spermidine levels were reduced while spermine levels increased. The substantial putrescine pool could have reached toxic levels within the fungus, causing the inhibition of growth observed. In contrast, TED-1 decreased putrescine and spermidine levels within P. avenae, while leaving spermine levels unchanged. TED-1 also increased soluble ODC activity within the fungus, but reduced soluble S-adenosylmethionine decarboxylase (AdoMetDC) activity. Further experiments indicated that TED-1's growth inhibition may not be related to binding at intracellular binding sites and effects on membrane integrity. It seems therefore, that different novel putrescine analogues may possess quite different modes of action. These results indicate that synthetic putrescine analogues possess considerable fungicidal activity.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Plant pathology.
• Colleges/Schools: College of Medical Veterinary and Life Sciences
• Supervisor's Name: Walters, Dr. D.R.
• Date of Award: 1993
• Depositing User: Enlighten Team
• Unique ID: glathesis:1993-72293
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 24 May 2019 15:12
• Last Modified: 23 Jul 2021 15:32
• URI: https://theses.gla.ac.uk/id/eprint/72293