Assertion: sweet potato's tuber | /r/HasProperty | important
Facets:
value: in africa
type: LOCATION
value: historically
type: TEMPORAL
Source sentences:
text: Non-Dioscorea tubers that were historically important in Africa include Plectranthus rotundifolius (the Hausa potato) and Plectranthus esculentus (the Livingstone potato); these two tuber crops have now been largely displaced by the introduction of cassava.