The role of myrosinase in the development of toxicity toward Nematospora in mustard seed

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Abstract
The toxicity of contaminated mustard seed toward Nematospora yeast was due to the action of endogenous myrosinase upon the glucosinolates, sinigrin from Brassicajuncea, and sinalbin from B. hirta seeds to produce toxic hydrolysis products. Allyl isothiocyanate from sinigrin was lethal at 20–35 μg/mL while p-hydroxybenzyl alcohol and p-hydroxybenzoic acid from sinalbin were toxic at >600 and >800 μg/mL, respectively. Two cultivars of rapeseed (B. campestris cv. Echo and cv. Candle) contained only trace amounts of sinigrin and sinalbin and were not toxic to the yeast. The activation of myrosinase during germination of oriental and yellow mustard and the production of toxic hydrolytic compounds may limit the spread of infection by reducing the reservoir of viable yeast in the seed. No evidence was obtained to suggest a role for these toxic products in resistance of the plant to invasion by Nematospora.