Linkage of the A locus for the presence of anthocyanin and fs10.1, a major fruit-shape QTL in pepper

The purple color of the foliage, flower and immature fruit of pepper (Capsicum spp.) is a result of the accumulation of anthocyanin pigments in these tissues. The expression of anthocyanins is controlled by the incompletely dominant gene A. We have mapped A to pepper chromosome 10 in a Capsicum annuum (5226) x Capsicum chinense (PI 159234) F-2 population to a genomic region that also controls anthocyanin expression in two other Solanaceous species, tomato and potato, suggesting that variation for tissue-specific expression of anthocyanin pigments in these plants is controlled by an orthologous gene(s). We mapped an additional locus, Fc, for the purple anther filament in an F2 population from a cross of IL 579, a C. chinense introgression line and its recurrent parent 100/63, to the same position as A, suggesting that the two loci are allelic. The two anthocyanin loci were linked to a major quantitative trait locus, fs10.1, for fruit-shape index (ratio of fruit length to fruit width), that also segregated in the F-2 populations. This finding verified the observation of Peterson in 1959 of linkage between fruit color and fruit-shape genes in a cross between round and elongated-fruited parents. The linkage relationship in pepper resembles similar linkage in potato, in which anthocyanin and tuber-shape genes were found linked to each other in a cross of round and elongated-tuber parents. It is therefore possible that the shape pattern of distinct organs such as fruit and tuber in pepper and potato is controlled by a similar gene(s).