AOBPreview originally published online on January 13, 2005
Annals of Botany 2005 95(4):601-608; doi:10.1093/aob/mci062
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Annals of Botany 95/4 © Annals of Botany Company 2005; all rights reserved
Inter- and Intra-specific Variation among Five Erythroxylum Taxa Assessed by AFLP
1 USDA ARS PSI ACSL, 10300 Baltimore Avenue, BARC-W, Beltsville, MD 20705, USA
* For correspondence. E-mail johnsone{at}ba.ars.usda.gov
Received: 5 March 2004 Returned for revision: 23 September 2004 Accepted: 15 November 2004 Published electronically: 13 January 2005
Background and Aims The four cultivated Erythroxylum taxa (E. coca var. coca, E. novogranatense var. novogranatense, E. coca var. ipadu and E. novogranatense var. truxillense) are indigenous to the Andean region of South America and have been cultivated for folk-medicine and, within the last century, for illicit cocaine production. The objective of this research was to assess the structure of genetic diversity within and among the four cultivated alkaloid-bearing taxa of Erythroxylum in the living collection at Beltsville Agricultural Research Center.
Methods Amplified fragment length polymorphism (AFLP) fingerprinting was performed in 86 Erythroxylum accessions using a capillary genotyping system. Cluster analysis, multidimensional scaling (MDS) and analysis of molecular variance (AMOVA) were used to assess the pattern and level of genetic variation among and within the taxa.
Key Results A clear distinction was revealed between E. coca and E. novogranatense. At the intra-specific level, significant differentiation was observed between E. c. var. coca and E. c. var. ipadu, but the differentiation between E. n. var. novogranatense and E. n. var. truxillense was negligible. Erythroxylum c. var. ipadu had a significantly lower amount of diversity than the E. c. var. coca and is genetically different from the E. c. var. ipadu currently under cultivation in Colombia, South America.
Conclusions There is a heterogeneous genetic structure among the cultivated Erythroxylum taxa where E. coca and E. novogranatense are two independent species. Erythroxylum coca var. coca is most likely the ancestral taxon of E. c. var. ipadu and a founder effect may have occurred as E. c. var. ipadu moved from the eastern Andes in Peru and Bolivia into the lowland Amazonian basin. There is an indication of artificial hybridization in coca grown in Colombia.
Key words: Erythroxylum coca var. coca, Erythroxylum coca var. ipadu, Erythroxylum novogranatense var. novogranatense, Erythroxylum novogranatense var. truxillense, AFLP markers, genetic variation, cultivated coca, DNA fingerprinting, cocaine, tropical plants