Allelochemicals Biologica... - Name

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ANA LUISA ANAYA
we cannot eliminate the use of herbicides, their use can be reduced by exploiting
allelopathy as an alternate weed management tool for crop production against weeds
and other pests.
The use of allelopathy for controlling weeds could be either through directly
utilizing natural allelopathic interactions, particularly of crop plants, or by using
allelochemicals as natural herbicides. In the former case, a number of crop plants
with allelopathic potential can be used as cover, smother, and green manure crops for
managing weeds by making desired manipulations in the cultural practices and
cropping patterns. These can be suitably rotated or intercropped with main crops to
manage the target weeds (including parasitic ones) selectively. Even the crop mulch/
residues can also give desirable benefits. The allelochemicals present in the higher
plants as well as in the microbes can be directly used for weed management along
with the management of some herbicides (Singh et al., 2003b).
Singh et al. (2003b) also mentioned that the bioefficacy of allelochemicals can be
enhanced by structural changes or the synthesis of chemical analogues based on them.
Further, in order to enhance the potential of allelopathic crops, several improvements
can be made with the use of biotechnology or genomics and proteomics. In this context
either the production of allelochemicals can be enhanced or the transgenics with
foreign genes encoding for a particular weed-suppressing allelochemical could be
produced. These authors comment that in the former, both conventional breeding and
molecular genetical techniques are useful. However, with conventional breeding being
slow and difficult, more emphasis is laid on the use of modern techniques such as
molecular markers and the selection aided by them. Although the progress in this
regard is slow, nevertheless some promising results are coming and more are expected
in future. In this sense, is important to point out that the potential use of transgenic
plants and other genetically modified organisms (GMO’s) with such or other proposal,
cause a strong controversial with the principles of organic agriculture defined and
established by the International Federation of Organic Agriculture Movements
(IFOAM) founded with the aim to promote an agriculture that is ecologically,
economically, and socially sustainable. IFOAM is opposed to genetic engineering in
agriculture, in view of the unprecedented danger it represents for the entire biosphere
and the particular economic and environmental risks it poses for organic producers
(IFOAM, 2002) * .
Using a soil bioassay technique, Conkling et al. (2002) assessed seedling growth
and incidence of disease of wild mustard (Brassica kaber) and sweet corn (Zea mays)
in soil from field plots that received either of two treatments: incorporated red clover
(Trifolium pratense) residue plus application of compost (‘amended soil’), or
application of ammonium nitrate fertilizer (‘unamended soil’). Soils were analyzed
for percent moisture, dissolved organic carbon, conductivity, phenolics, and nutrient
content. A trend toward greater incidence of Pythium spp. infection of wild mustard
seedlings grown in amended soil was observed during the first 40 days after
* IFOAM, 2002: International Federation of Organic Agriculture Movements (IFOAM). Position on Genetic
Engineering and Genetically Modified Organisms. http://www.ifoam.org/pospap/ge_position_0205.html 2002.