Baghestani et al. (1999) investigated the phytotoxic
effects of root exudates of highly competitive (HC) and
less competitive (LC) cultivars of wheat, oat and two-
and six-rowed barley on germination and seedling
growth of wild mustard. HC wheat cultivars were found
to be more phytotoxic compared to LC cultivars. Root
exudates of cereal cultivars mainly contained phenolic
acids. These authors concluded that vanillic and
o-coumaric acids and scopoletin are likely to be
responsible for phytotoxic effects of wheat, barley and
oat, and should be considered for use when monitoring
the breeding potential for allelopathic crop cultivars.