Demonstration of orobanchicidal effects of allelochemical
released by cereals suggests the potential of developing a
practical broomrape management strategy using cereals as
green manure crops or as intercrops. However, determining the
toxicity of specific compounds involved in broomrape
suppression is only part of the information needed to optimize
this management strategy. Further research is needed to
understand the fate of allelochemicals in soil and their use for
broomrape control. In addition to determining the concentration
of these compounds in soil, an appropriate cultivar
containing large concentrations of allelochemicals must be
used. For example, the amount of hydroxamic acids varies
greatly with plant age, organ, and cultivar, being affected by
water stress conditions, high temperatures, and fertilization.48
Hydroxamic acids do not persist for long periods.49,50 This
degradation in soil is interesting as this avoids the risks of
accumulation of toxic compounds in soil. However, this also
implies the need to adjust the timing of incorporation that
should coincide with the time of germination of O. crenata in
the soil.
Breeding programs focused on selection of host genotypes
for high root exudation levels of germination or radicle growth
inhibitors could identify better candidates for intercrops to be
used in a control strategy. Allelopathic potential seems to be a
quantitative trait of complex inheritance and highly influenced
by environment and, thus, difficult to breed. Allelophatic
potential of cereal crops can be enhanced by classical or
marker-assisted breeding provided that genetic variation and
proper screening methods exist. For instance, significant
variation in the level of scopoletin has been reported within
oat accessions, with accession PI-2666281 producing the
highest scopoletin content and showing the highest inhibition
of the growth of the tested Brassica weed.2 Such variation in the
content of various allelochemicals and in allelopathic activity
exists within various cereal crops cultivars, which may allow for
the selection of more allelopathic cultivars.1 In addition,
understanding the genes responsible for the biosynthesis and
release of allelochemicals will allow their incorporation in highyielding
cultivars by genetic manipulation.