Discovery of novel unfunctional pAMT allele pamt(10) causing loss of pungency in sweet bell pepper (Capsicum annuum L.)

Pungency is a characteristic trait of pepper (Capsicum spp.). Two genes, Pun1 and pAMT, are known as determinative factors of pepper pungency. To date, it has been considered that most bell-type sweet peppers (called piman and paprika, in Japan) possess the identical mutated Pun1 allele, pun1, whereas pAMT mutated non-pungent pepper has been found only in non-bell-type pepper. In this study, to reconsider the uniformity of the source of non-pungency in sweet bell pepper and explore new genetic resources, the presence of pun1 was investigated in 26 sweet bell pepper varieties. Among them, a seemingly common sweet bell pepper ‘Color Piman Yellow’ had the intact Pun1, in spite of its non-pungency. Sequencing and linkage analyses revealed that ‘Color Piman Yellow’ possessed a novel mutated pAMT allele, pamt(10), that has a nonsense substitution at the 11th exon responsible for non-pungency. This is the first pAMT mutant to be found in sweet bell pepper. The finding that there was a pAMT mutant in sweet bell pepper suggests the possibility that more pAMT mutants exist unconsciously in other sweet bell peppers. The discovery of a new factor of non-pungency contributes to expanding the genetic diversity of sweet pepper varieties.