C. Olivier et al., Variation in allyl isothiocyanate production within Brassica species and correlation with fungicidal activity, J CHEM ECOL, 25(12), 1999, pp. 2687-2701
Bassica nigra (black mustard) and B. juncea (Indian mustard) genotypes were
tested for pathogen suppression and release of allyl isothiocyanate (AITC)
, a fungitoxic volatile produced in mustard tissue after enzymatic hydrolys
is of allyl glucosinolate (sinigrin). In bioassays, 28 genotypes of B. nigr
a and 35 genotypes of B, juncea were screened for inhibition of the potato
pathogens Helminthosporium solani and Verticillium dahliae by volatiles rel
eased from macerated leaf tissue. Release of AITC from plant tissue was qua
ntified by gas chromatography; isothiocyanate profiles were determined by h
eadspace analysis. All mustard genotypes produced compounds that suppressed
radial growth of both fungi. Growth suppression and AITC release differed
significantly (P < 0.001) among genotypes of B. nigra and B. juncea. Mustar
d treatments releasing >1.2 mg AITC/g plant tissue were fungicidal to both
pathogens. Headspace analysis confirmed that allyl glucosinolate was the ma
jor glucosinolate in all genotypes of B. nigra tested; most genotypes also
produced 2-phenylethyl-isothiocyanate (ITC). Brassica juncea genotypes prod
uced variable amounts of AITC and other volatiles with antimicrobial activi
ty, including 2-phenylethyl-ITC, benzyl-ITC, and 3-butenyl-ITC. Evaluating
mustards from geographically diverse locations allowed selection of mustard
genotypes that may be useful in breeding programs designed to develop dise
ase-suppressing green manure cultivars.