Endogenously induced secondary dormancy in seeds of Striga hermonthica

At the end of the cropping season in November 1994, Striga hermonthica seed populations were collected in northern Benin (in the Atacora and Borgou de partments). Host crops included Zea mays L. (corn), Pennisetum americanum ( pearl miller), and Sorghum bicolor (L.) Moench (sorghum). The seed populati ons were kept dry in the laboratory, and germination was tested regularly a fter 2 wk conditioning in the laboratory. The seeds passed through a state of primary dormancy, which was not the same for seed populations collected from Z. mays and S. bicolor fields and those collected from P. americanum f ields. The length of the primary dormancy was approximately 6 mo. After pas sing through primary dormancy (after- ripening), the seeds later went throu gh annual, recurrent states of secondary dormancy. Primary dormancy coincid ed with the dry season directly after maturity (i.e., between December 1994 and April 1995), and secondary dormancy coincided more or less with the su bsequent 1995/1996 and 1996/1997 dry seasons. It is concluded that the seco ndary dormancy pattern was endogenous. Germination percentages during the p eriod that coincided with the first rainy season after collection were gene rally higher than during the period that coincided with the second rainy se ason.