ABSTRACT
Genetic exchange between wild and cultivated sorghums occurs in nature. The appearance of weedy traits such as shattering and rhizomatousness (development of plants that propagate from rhizomes) in crop-wild hybrids of sorghum has often been used as evidence for such exchanges. The impact of unusual traits resulting from these introgressions in the nature of the resultant hybrids including the appearance of feral forms has not been widely studied and documented. Sorghum is one of the five most important grain crops in the world and is mainly cultivated in the developing world including Africa, the ancestral home of the crop. In many of these areas, volunteer, wild, and weedy forms exist both together with the crop and in nearby ruderal areas. Intermediary forms such as shattercanes are ubiquitous and exist in a continuum of forms ranging from those that closely resemble the wild to those nearly indistinguishable from the cultivated members of the same genus. Although there is no clear evidence for the existence of feral types emerging as a result of mutational dedomestication (endoferality), the existence of intermediary forms in most sorghum growing areas offers an empirical evidence for noxious weedy forms arising from continued introgression (exoferality) among different sorghum types. For instance, the most widely recognized noxious weed in the sorghum taxa, Sorghum halepense (johnsongrass), is a natural hybrid between the cultivated Sorghum bicolor and wild rhizomatous species S. propinquum.
