Abstract
The genus Capsicum is comprised of 5 domesticated and more than 30 wild species. The region of nuclear ribosomal DNA internal transcribed spacers (rDNA-ITS) has widely been used for species identification, but has rarely been used in Capsicum. In this study, the evaluation of genetic diversity and a phylogenetic analysis were conducted using rDNA-ITS of 28 Capsicum accessions, including five domesticated and two wild species. We surveyed six conventional keys of domesticated species and another five traits in Capsicum accessions. Specific morphological characteristics were found in C. annuum, C. baccatum, and C.pubescens. Three subclones of each accession were sequenced, and rDNA-ITS polymorphisms were detected in all accessions excluding C. annuum, suggesting that incomplete concerted evolution occurred in rDNA-ITS of Capsicum. The genetic diversity was evaluated using nucleotide polymorphism and diversity. C. annuum had the lowest genetic diversity of all species in this study. The phylogenetic tree formed a species-specific clade for C. annuum, C. baccatum, and C. pubescens. The C. chinense clade existed in the C. frutescens clade, implying that it was a cultivated variant of C. frutescens. C. chacoense likely belonged to the C. baccatum complex according to its morphologic and genetic features. This study indicated that the rDNA-ITS region can be used for simple identification of domesticated Capsicum species.
Highlights
The genus Capsicum has been cultivated since at least 6000 B.C. by Native Americans [1], and is produced at over 40 million tons per year worldwide [2]
The corolla color was yellow in C. baccatum, white or purple in C. annuum, white or greenish in C. chinense, greenish in C. frutescens and C. eximium, purple in
The C. eximium accession was likely to be misclassified because it is characterized by a purple corolla [35]; this misclassification was inferred from the following phylogenetic analysis based on rDNA-ITS in the present study
Summary
The genus Capsicum has been cultivated since at least 6000 B.C. by Native Americans [1], and is produced at over 40 million tons per year worldwide [2]. Fruits of the genus have good health properties such as stress relief and fat breakdown [3,4]. Capsaicin, which is the main pungent component of Capsicum, has attracted much attention because of beneficial health properties [3,5]. The genus has five domesticated species, C. annuum, C. baccatum, C. chinense, C. frutescens, and. C. pubescens, and more than thirty wild species [6,7]. The origin of the Capsicum genus is postulated to be along the Andes of western to north-western South America [8].
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