Submitted to: Georgia Journal of Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2004
Publication Date: 8/20/2004
Citation: Jarret, R.L., Dang, P.M. 2004. Revisiting the waxy locus and the capsicum annum l. complex. 2004 Georgia Journal of Science 62:117-133.
Interpretive Summary: The USDA genebank in Griffin, GA maintains thousands of varieties of peppers representing various species of Capsicum. The three principal cultivated species of pepper represented in the Griffin genebank are Capsicum annum, C. frutescens and C. chinense. Each of these species has unique fruit and quality characteristics. Plants of the same species can be intercrossed, while those of different species cannot. Hence, scientists request species for their research based on the characteristics presumed to be associated with a particular species, and the presumed ability of that species to be intercrossed. When specific varieties are requested by scientists, it is generally assumed that materials are correctly classified. However, this is not always the case. The three principle species of pepper share many characteristics in common. This makes it difficult, in some instances, to correctly classify these. We evaluated a genetic approach using DNA sequence information to determine if DNA sequence data at the waxy locus could be utilized to classify individual pepper varieties to determine which species they were - Capsicum annuum, C. frutescens or C. chinense. Our results indicated that this approach was useful in identifying varieties of Capscium annuum, but it did not differentiate C. frutescens from C. chinense.
Technical Abstract: Waxy locus introns from 35 accessions of the species comprising the Capsicum annuum complex ©. Annuum C. frutescens and C. chinense, C. baccatum, C. chacoense and C. pubescens were cloned and sequenced. These data were combined with existing GeneBank waxy intron data from the same species, C. tovarii, C. ciliatum, Lycianthes heteroclite, L. lenta, and L. glandulosa in order to determine the phylogenetic relationships within this group of plant materials, and to re-examine the strength of the delimination of the members of the C. annuum complex provided previously by analysis of indel and transition/transversion polymorphisms at this locus. Included in the subject materials analyzed were genotypes of C. annuum, C. chinense and C. frutescens that possessed characteristics presumed to be unique to other species in this complex. PAUP analysis revealed strong support of Capsicum at the genus level. Capsicum ciliatum was sister species to C. tovarii, which was sister species to a clad containing the five cultivated taxa and C. chacoense. The separation of C. baccatum and C. pubescens from the other species was well supported, and the separation of C. annuum from C. chinense and C. frutescens was moderately supported based on bootstrap values. In contrast, no clear separation of C. chinense from C. frutescens was observed.