Analytical Evaluation of Capsicum Germplasm Resources for Genetic Improvement of Aroma and Flavor In Pepper Fruit

Capsicum germplasm includes five domesticated species and 25 wild species.  C. annuum is widely grown worldwide and includes the economically important sweet bell pepper.  Related germplasm resources offer rich diversity for genetic improvement of C. annuum.  Introgression of novel fruit flavor attributes from domesticated and wild species affords new opportunities to improve pepper fruit flavor.  We have identified Capsicum accessions with unique aroma and flavor attributes.  A gas chromatography (GC)-mass spectroscopy-olfactory detection system was utilized to characterize fruit aroma volatiles, and GC-flame ionization detection was used for quantification of TMS sugars and organic acids.  Over 150 volatiles have been identified in selected accessions, half of which have not been characterized previously in fruit of C. annuum.  Some accessions with unique flavor attributes were distinct from other accessions, particularly C. annuum cultivars, in having relatively high concentrations of various esters with fruity, floral or uncharacterized aromas, sesqueterpenes with woody, spicy, herbal and uncharacterized aromas and relatively polar volatiles some of which had malodorous odors.  Many individual volatiles, mostly aldehydes, ketones and alcohols, having ethereal or green-grassy aromas and two pyrazines having ginseng or bell pepper aromas were present in all accessions evaluated.  Concentrations of most volatiles decreased during fruit ripening whereas 1-penten-3-ol, 3-pentanone, 1-hexanol and (E)-2-hexen-1-ol increased.  Preliminary evaluations indicate variations in the concentrations of ascorbic, citric, malic, oxalic, fumaric, pyroglutamic, and/or shikimic acids, and sucrose, glucose and fructose.  Genes that influence flavor quality in Capsicum are being identified by analysis of intra- and inter-specific populations.  Phenotypic characterization of over 250 Capsicum accessions and select inbred backcross populations should provide breeding material for development of C. annuum stocks with enhanced fruit flavor.