Abstract
An overview of the metabolic diversity in ripe fruits of a collection of 32 diverse pepper (Capsicum sp.) accessions was obtained by measuring the composition of both semi-polar and volatile metabolites in fruit pericarp, using untargeted LC–MS and headspace GC–MS platforms, respectively. Accessions represented C. annuum, C. chinense, C. frutescens and C. baccatum species, which were selected based on variation in morphological characters, pungency and geographic origin. Genotypic analysis using AFLP markers confirmed the phylogenetic clustering of accessions according to Capsicum species and separated C. baccatum from the C. annuum–C. chinense–C. frutescens complex. Species-specific clustering was also observed when accessions were grouped based on their semi-polar metabolite profiles. In total 88 semi-polar metabolites could be putatively identified. A large proportion of these metabolites represented conjugates of the main pepper flavonoids (quercetin, apigenin and luteolin) decorated with different sugar groups at different positions along the aglycone. In addition, a large group of acyclic diterpenoid glycosides, called capsianosides, was found to be highly abundant in all C. annuum genotypes. In contrast to the variation in semi-polar metabolites, the variation in volatiles corresponded well to the differences in pungency between the accessions. This was particularly true for branched fatty acid esters present in pungent accessions, which may reflect the activity through the acyl branch of the metabolic pathway leading to capsaicinoids. In addition, large genetic variation was observed for many well-established pepper aroma compounds. These profiling data can be used in breeding programs aimed at improving metabolite-based quality traits such as flavour and health-related metabolites in pepper fruits.Electronic supplementary materialThe online version of this article (doi:10.1007/s11306-012-0432-6) contains supplementary material, which is available to authorized users.
Highlights
Pepper (Capsicum spp.) is one of the most important fruit crops worldwide
Our results showed that the diversity of volatile and semi-polar metabolites detected in the accessions separated them according to species and pungency, which correlated well with the phylogenetic relationships measured using amplified fragment length polymorphism (AFLP) molecular markers
3.1 Genetic diversity of Capsicum accessions based on AFLP analysis
Summary
Pepper (Capsicum spp.) is one of the most important fruit crops worldwide. It is cultivated all over the world, primarily in the tropical and subtropical countries. We recently showed that different Capsicum accessions display a large variation in morphological characters as well as in the levels and composition of the above-mentioned health related metabolites (Wahyuni et al 2011). The accessions belong to four widely cultivated species: Capsicum annuum, Capsicum chinense, Capsicum baccatum, and Capsicum frutescens. These four species can be intercrossed and produce fertile hybrids (Pickersgill 1997). Based on the range of capsaicinoid levels the accessions can be categorized into non-pungent, low, mild and highly pungent (Howard and Wildman 2007)
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