Analysis by GC/MS/MS showed that a worldwide collection of 58 wheat accessi
ons differed significantly in the production of seven phenolic acids in the
roots of 17-day-old wheat seedlings. The allelochemical contents among whe
at accessions ranged from 24.5 to 94.5, 19.9 to 91.7, 3.7 to 15.4, 2.2 to 3
8.6, 1.0 to 42.2, 19.3 td 183.6, and 11.7 to 187.6 mg/kg of root dry weight
for p-hydroxybenzoic, vanillic, cis-p-coumaric, syringic, cis-ferulic, tra
ns-p-coumaric, and trans-ferulic acids, respectively. trans-Ferulic acid wa
s identified as the most predominant phenolic acid in the roots. Phenolic a
cids, with the exception of syringic acid, were more concentrated in roots
than in shoots. Significant correlation was found between the roots and the
shoots in the contents of vanillic, cis-p-coumaric, syringic, trans-p-coum
aric, and trans-ferulic acids, and in the content of each structural group
of phenolic acids. Wheat accessions with high levels of total identified ph
enolic acids in the roots were generally strongly allelopathic to the growt
h of annual ryegrass.