1. The mechanism of protection of maize from striga by intercropping Desmodium uncinatum is due to an allelopathic root exudates.

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. 

2. 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.

3. The biological activity of some components of the root exudate stimulate germination (e.g. uncinanone B, 1; see Fig 1), while the biological activity of other components inhibit the length of the radical after germination (e.g. uncinanone C, 2; see Fig 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).

4. 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.

5. 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.