Using an adaptation of the Cut-root technique, twenty-one varieties of soybean were screened at 10, 15 and 20 days after planting (DAP) for the stimulation of S. hermonthica seed germination. The varieties were TGX1649-11F, TGX1740-7F, TGX1660-15F, TGX1740-2F, TGX1670-3F, TGX1674-3F and SAMSOY-2. Other varieties tested included TGX1681-3F, TGX1479-1E, TGX923-2E, TGX1440-1E, TGX1448-2E, TGX1660-19F, TGX1519-10F, TGX1019-2EN, TGM-344, TGX1019-EB, TGX1485-1D, TGX536-02D, TGM-351 and TGX849-3B. The strigol analogue, GR-24, was used as the control. The germination of S. hermonthica seeds that was stimulated by GR-24 was significantly higher (P≤0.01) than that stimulated by all the soybean varieties at all the periods. The most promising varieties were TGX1681-3F, TGX1479-1 E, TGX1649-11F and SAMSOY-2 with Specific Effectiveness Index (SEI) values of 0.76, 0.75, 0.58 and 0.54, respectively. The other varieties that showed promise include TGX1740-7F, TGX923-2E TGX1440-1 E and TGM344 with SEI values of 0.44, 0.44, 0.45 and 0.44, respectively. There was no relationship between the age of the plant and potency of its root exudates, except for TGX1649-11F, TGM-344 and TGX1681-3F where activity increased with age from 10DAP to 20DAP. These varieties may therefore be used in field crop rotation systems as an option for the management of S hermonthica.
Keywords: witchweed, soybean, trapcropping, crop rotation, Striga hermonthica
[Global Jnl Agric Res Vol.2(1) 2003: 25-32]