Study of the compounds responsible for pungency trait in pepper (Capsicum spp.): Analytical techniques and genetic and molecular analysis

One of the important quality attributes of pepper (Capsicum spp.) is pungency, which is caused by the presence of a group of alkaloids known as capsaicinoids. The two major capsaicinoids are capsaicin and dihydrocapsaicin. In this work, three different aspects related to pungency trait have been studied: (i) determination and quantification of some of the compounds responsible for pungency; (ii) gene action that controls the inheritance of some individual capsaicinoids; and (iii) some genetic sequences related to capsaicinoid biosynthesis.;A liquid chromatography-electrospray ionization/time of flight mass spectrometry method has been developed and validated for the determination of capsaicin and dihydrocapsaicin in pepper fruit extracts. The developed method has been applied to the identification and quantification, with high selectivity, sensitivity, and sufficient reproducibility, of capsaicin and dihydrocapsaicin in fruit extracts from different Capsicum genotypes and the contents of both capsaicinoids varied largely. The quantitative inheritance of capsaicin and dihydrocapsaicin contents in fruits has been studied in an intraspecific cross of Capsicum annuum L. across two environments, spring and summer. Capsaicin and dihydrocapsaicin contents varied largely among generations, and these did not respond similarly in producing these capsaicinoids when their fruits were grown in spring and summer. Heterosis for the pungency trait was found and a transgressive segregation occurred. Also, the type of gene action was a model with epistatic effects, varying between capsaicin and dihydrocapsaicin.;During the analysis of expressed sequences tag related to capsaicinoid biosynthesis, a SNP associated with pungency and an additional sequence possibly also relate to such trait have been identified. This SNP marker was associated with phenotypic pungent character in eight Capsicum tested species. The genetic sequence, where the SNP is located, showed 100% homology with a partial sequence, named Catf2. The characterization of a large and diverse number of Capsicum genotypes, belonging to several species, by their pungent phenotype and for the presence of Pun1 and Catf2 revealed the existence of several pungent genotypes where the Pun1 allele was not detected, whereas the Catf2 partial sequence and the associated pungent SNP it was present.