Two types of isoflavanoid constituents have been found in
compositionally complex root exudates of Desmodium uncinatum:
germination stimulants and haustorium inhibitors. The combined action
of these allelochemics provide a novel, in situ mechanism of
continuously depleting Striga seeds from the soil, so far
demonstrated in experimental Desmodium-maize intercrops. Some of the
allelochemics have been isolated and characterized. The differences
in activities of these compounds suggest relatively specific
structural requirements for germination stimulatory and haustorium
inhibitory activities. The implications for screening for Desmodium-type
Striga suppression attribute and for a biotechnological
approach to transferring this attribute to other crops will be
highlighted. Specifically, the presentation will address the
following topics: 1) the diversity of Desmodium root chemistry and
role, if any, in Striga suppression; 2) the occurrence of
isoflavanoid biochemistry in Leguminosae and 3) other families and
probability of finding Desmodium-type secondary compounds; and
prospects of transferring Desmodium biochemical attributes to other
crops.
