Clonal diversity, cultivar traits, geographic dispersal, and the ethnotaxonomy of cultivated Qat (Catha edulis, Celastraceae)

Authors: TEMBROCK, LUKE - Colorado State University; SIMMONS, MARK - Colorado State University; Richards, Christopher; Reeves, Patrick; Reilley, Ann; CURTO, MANUEL - University Of Natural Resources & Applied Life Sciences - Austria; MEIMBERG, HARALD - University Of Natural Resources & Applied Life Sciences - Austria; NGUGI, GRACE - National Museums Of Kenya; DEMISSEW, SEBSEBE - Addis Ababa University; ABDUL WALI, AL-KHULAIDI - University Of Sanaa; AL-THOBHANI, MANSOOR - Sana'A University; Simpson, Sheron; VARISCO, DANIEL - University Of Chicago

Submitted to: Economic Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2020
Publication Date: 8/19/2020
Citation: Tembrock, L.R., Simmons, M.P., Richards, C.M., Reeves, P.A., Reilley, A.A., Curto, M.A., Meimberg, H., Ngugi, G., Demissew, S., Abdul Wali, A., Al-Thobhani, M., Simpson, S.A., Varisco, D.M. 2020. Clonal diversity, cultivar traits, geographic dispersal, and the ethnotaxonomy of cultivated Qat (Catha edulis, Celastraceae). Economic Botany. 74:273-297. https://doi.org/10.1007/s12231-020-09501-4.
DOI: https://doi.org/10.1007/s12231-020-09501-4

Interpretive Summary: Studies of the diversity of vegetatively propagated crop species are often hampered by inexact naming conventions whereby a single clone grown in different areas are given separate common names. This report describes the the diversity and ethnotaxonomy of the species Catha edulis a plant with important cultural and economic significance that is consumed daily in eastern Africa. Using micro satellite DNA markers, the study was able to identify the identity geographic distribution and origin of the major cultivated genotypes cultivated in the east African rift region and central Ethiopia. The results help clarify the ongoing domestication process of this species.

Technical Abstract: Farmers and traders have developed a system of names to refer to different qat (Catha edulis)cultivars, using stem color as the primary trait to differentiate them. In this study, we tested if named cultivars from Ethiopia, Kenya, and Yemen represent genetic clusters. We also quantified clonal reproduction and tracked the geographic dispersal of cultivated-qat genotypes. We used microsatellite genotypes of specimens collected from across the major qat growing regions and population-structure analyses to test whether cultivar name, elevation, and/or clonality were associated with a given genetic cluster, genotype,or locus. Specimens were also mapped to determine whether traits,genotypes, or genetic clusters were geographically restricted. The only significant association of genotype to the traits examined was to clonality.Stem color was found to be a plastic trait because specimens of the same genotype have different colored stems. A single cultivar name was often applied to numerous clonal groups and genetic clusters, creating widespread homonymy in the ethnotaxonomy of qat cultivars. The East African Rift in central Ethiopia was found to be a barrier to the exchange of both clonal groups and certain cultivar names. In Kenya, both cultivar names and clonal groups were broadly dispersed geographically. Nearly all of the clonal groups originated from the Mt Kenya/Meru area in central Kenya.