Allelic Variation in a Putative Gene Related to Pungency in Pepper (Capsicum spp.)

The compounds called capsaicinoids, responsible for pungency in peppers (Capsicum spp.), exhibit a wide genetic and environmental control variation. Pungency in pepper is an interesting quality trait that requires more knowledge about its genetic control. Up to now, not all the genes involved in the capsaicinoid biosynthetic pathway have been characterized. From previous work, a partial DNA sequence, possibly related to pungency, was identified and using the genome walking technique, a complete DNA sequence was obtained from C. annuum 'Yolo Wonder'. The aim of this work was to study this DNA sequence in several pepper genotypes. The putative gene was sequenced in six genotypes from different species: three model genotypes, one non-pungent C. annuum 'Yolo Wonder' and two pungent, C. annuum 'SCM-334' and C. chinense 'Habanero'; and other three pungent genotypes, selected by their characteristics concerning to pungency trait, C. chinense 'C-158', C. frutescens 'C-126', and C. baccatum 'C-235'. For this purpose, several pairs of primers were designed along the above sequence and they were used to obtain the target DNA sequence. These results showed variability. Among the observed differences, a deletion was found only in the non-pungent genotype, and this result was confirmed when more non-pungent genotypes were studied. Also, several Single Nucleotide Polymorphisms, either genotype-specific or pungent-specific were found. Finally, differences along the upstream DNA sequence region in C. baccatum 'C-235' were observed. The detected allelic variation might be further investigated, to better understand its effect at the phenotypic level of the pungency trait.