Clonality of Pawpaw (Asimina triloba) Patches in Kentucky

Pawpaw [Asimina triloba (L.) Dunal] is a tree-fruit (see overleaf, page 2) native to the southeastern region of the United States. Kentucky State University serves as the USDA-National Clonal Germplasm Repository for pawpaw, therefore assessing genetic diversity across the pawpaw's native range is a high priority. Pawpaw is usually found in large patches as an understory tree and root suckering likely occurs. To determine if native pawpaw patches are clonal, DNA was extracted from leaf samples collected from trees in six native patches in three counties in central Kentucky. Two ISSR-PCR primers yielded three polymorphic and six monomorphic markers in the six patches. Three patches did not display any polymorphic markers in each patch, suggesting they were clonal. However, three other patches did show polymorphic markers within each patch, indicating these patches were not clonal and contained trees of at least two genotypes within each patch. This study suggests that to assess the genetic diversity of a pawpaw patch or local population, more intensive sampling strategies will be required.