Endogenously induced secondary dormancy in seeds ofStriga hermonthica

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Abstract
At the end of the cropping season in November 1994, Striga hermonthica seed populations were collected in northern Bénin (in the Atacora and Borgou departments). Host crops included Zea mays L. (corn), Pennisetum americanum (pearl millet), and Sorghum bicolor (L.) Moench (sorghum). The seed populations were kept dry in the laboratory, and germination was tested regularly after 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 fields. The length of the primary dormancy was approximately 6 mo. After passing through primary dormancy (after-ripening), the seeds later went through annual, recurrent states of secondary dormancy. Primary dormancy coincided with the dry season directly after maturity (i.e., between December 1994 and April 1995), and secondary dormancy coincided more or less with the subsequent 1995/1996 and 1996/1997 dry seasons. It is concluded that the secondary dormancy pattern was endogenous. Germination percentages during the period that coincided with the first rainy season after collection were generally higher than during the period that coincided with the second rainy season.