Effects of garlic (<Emphasis Type="Italic">Allium sativum</Emphasis>) juice containing allicin on <Emphasis Type="Italic">Phytophthora infestans</Emphasis> and downy mildew of cucumber caused by <Emphasis Type="Italic">Pseudoperonospora cubensis</Emphasis> |
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Authors: | Daniela Portz Eckhard Koch Alan J Slusarenko |
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Institution: | (1) Department of Plant Physiology, RWTH Aachen University, 52056 Aachen, Germany;(2) Federal Research Centre for Cultivated Crops (JKI), Institute for Biological Control, Heinrichstr. 243, 64287 Darmstadt, Germany |
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Abstract: | The volatile antimicrobial substance allicin (diallylthiosulphinate) is produced in garlic when the tissues are damaged and
the substrate allicin (S-allyl-l-cysteine sulphoxide) mixes with the enzyme alliin-lyase (E.C.4.4.1.4). Allicin undergoes thiol-disulphide exchange reactions
with free thiol groups in proteins and it is thought that this is the basis of its antimicrobial action. At 50 μg ml-1, allicin in garlic juice inhibited the germination of sporangia and cysts and subsequent germ tube growth by Phytophthora infestans both in vitro and in vivo on the leaf surface. Disease severity in P. infestans-infected tomato seedlings was also reduced by spraying leaves with garlic juice containing allicin over the range tested
(55–110 μg ml−1) with an effectiveness ranging from approximately 45–100%. Similarly, in growth room experiments at concentrations from 50–1,000 μg
ml−1, allicin in garlic juice reduced the severity of cucumber downy mildew caused by Pseudoperonospora cubensis by approximately 50–100%. These results suggest a potential for developing preparations from garlic for use in specialised
aspects of organic farming, e.g. for reducing pathogen inoculum potential and perhaps for use under glass in horticulture. |
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Keywords: | Natural fungicides Tomato leaf blight Plant antibiotic Antimicrobial Phytoanticipin |
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