Implications of seed dormancy for control of Striga hermonthica in Ghana

Freshly collected seeds of Striga hermonthica were conditioned (in darkness ) at various constant temperatures (20 - 35 degrees C) and water potentials (0 to -2MPa) for periods up to 35 d to observe the effects of temperature and water potential on germination. In general germination increased as the water potential during conditioning increased from -2 to 0 MPa irrespectiv e of temperature. Maximum germination occurred at 25 degrees C and 0 MPa af ter 10-14 days conditioning. Restricted seed germination was also observed after conditioning at low to medium water potentials over the entire temper ature range. The optimum conditioning temperature and period appeared to re main the same (i.e. 25 degrees C) with decrease in water potential. Results are discussed in terms of predicting the optimum planting dates of suscept ible crops as a function of period from onset of seasonal rains. Field tria ls in Northern Ghana to validate these predictions will also be described.