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PI:
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Zeyaur Khan and Ahmed
Hassanali
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Contact details
Dr. Zeyaur Khan, ICIPE
P. O. Box 30772,
Nairobi, Kenya
Phone: +254 (2) 861680-4
Fax: 254 2 860110
Email direct from site:
zkhan@icipe.org
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Grantee:
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ICIPE
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Amount:
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US $75,000
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Duration:
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Three Years
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Publication: Z. R. Khan, A. Hassanali,
W. Overholt, T. M. Khamis, A. M. Hooper, J. A. Pickett, L. J. Wadhams,
C. M. Woodcock. 2002. Control of the witchweed Striga
hermonthica by intercropping with Desmodium uncinatum spp.
and the mechanism defined as allelopathic. J. Chem. Ecol.
28:1871-1885.
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A group of
structurally related isoflavanoid compounds have been isolated from
this allelopathic root exudate by bioassay-guided HPLC and their
structure elucidated by Microprobe-NMR analysis.
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The biological
activity of some components of the root exudate stimulate germination
(e.g. uncinanone B, 1), while the biological activity of other
components inhibit the length of the radical after germination (e.g.
uncinanone C, 2). This is the first example of a newly
identified, potential allelopathic mechanism to prevent S.
hermonthica parasitism.
Publication: Muniru K. Tsanuo, Ahmed
Hassanali, Antony M. Hooper, Zeyaur Khan, Festus Kaberia, John A.
Pickett, Lester J. Wadhams. 2003. Isoflavanones From The
Allelopathic Aqueous Root Exudate Of Desmodium uncinatum.
Phytochemistry (accepted).
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Polar fractions
from the allelopathic root exudate are the most potent inhibitors of
radical length. A number of compounds have been isolated from these
fractions by HPLC purification. Structure elucidation is now in
progress.
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Desmodium intortum
shows greater drought tolerance than D. uncinatum and has been
used successfully in the field to control striga in sorghum. Even in
the first season of protection, yields were over 2.2 tonne/ha compared
with ca 0.8 tonne/ha for control.
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