Abutilon theophrasti is one of the most problematic weeds worldwide. Rye
mulches, rich in benzoxazinoids, could not suppress Abutilon (Herbiseeds) due
to its avoidance of high BOA/BOA detoxification product accumulation and
phytotoxic 2-aminophenoxazinone production. Since Abutilon theophrasti seed
coats harbour a variety of fungi and bacteria, a participation of those organisms
in BOA degradation was assumed. The avoidance of high detoxification
product/BOA accumulation in the roots was correlated with the presence of the
Zygomycete Actinomucor elegans, which is known to colonize Abutilon seed
coats. The microorganism(s) produced plant growth promoting compounds,
whereby tryptophan excretion was stimulated by BOA. In Fenton reactions with
BOA, tryptophan accelerates the destruction of the allelochemical via
hydroxylated BOA molecules, when used in defined ratios. Destruction of BOA
via hydroxylated molecules presents a new pathway for BOA degradation
without accumulation of 2-aminophenoxazinone. During this process tryptophan
is also degraded. Applications of high concentrations of tryptophan led,
however, to a higher, channelled synthesis of BOA-6-O-glucoside in the roots,
probably to slow down oxygen consuming Fenton reactions. From all possible
hydroxylated BOA molecules, BOA-6-OH is the best substrate for Oglucosylation.
Incubations in presence of the mono-oxygenase effector 2-
bromo-4´-nitroacetophenone revealed that those enzymes are mainly
responsible for BOA-6-OH synthesis and only a minor part results from Fenton
reactions. The study elucidates the important role of plant-microorganism
associations in the survival of allelopathic attacks