Light-yellow Coloration of Sweet Pea (Lathyrus odoratus L.) Flowers is Caused by Carotenoid and Regulated by a Single Recessive Gene

Abstract

There are light-yellow flower cultivars of sweet pea (Lathyrus odoratus L.), but no deep-yellow ones. Observation of sweet pea flowers under ultraviolet and blue light suggested that carotenoids are responsible for the light-yellow coloration. We carried out both spectroscopic and high-performance liquid chromatography (HPLC) analyses of floral extracts of a light-yellow cultivar, ‘Artemis’, and revealed that the responsible pigments are not flavonoids, but carotenoids, among which acylated lutein is a major component. Because lutein is the pigment responsible for the deep-yellow color of flowers in other plants, we expect to be able to generate deep-yellow flower cultivars of sweet pea. The R and C loci are complementary genes regulating biosynthesis of anthocyanin pigments responsible for the cyanic coloration in sweet pea flowers. In progenies obtained by crossing ‘Artemis’ and a white cultivar, ‘Diana White’, whose genotype is RRcc, the F1 plants had a red flower phenotype only, and the F2 plants had four coloration phenotypes that were white, yellow, red and a combination of yellow and red. Furthermore, the F1 plants, obtained by crossing ‘Artemis’ and another yellow cultivar, ‘Stella’, had a combination of yellow and red flower phenotype only. These data indicate that the genotype of ‘Artemis’ is rrCC and the yellow coloration trait is regulated by a single recessive gene, y, and furthermore, that the y gene is not in linkage with the R or C allele. The theoretical segregation ratio of the F2 plants’ phenotypes obtained by crossing ‘Artemis’ as one parent in the case that Y, R and C loci are independent of each other are presented. We also found some cyanic color cultivars containing higher amounts of carotenoids than ‘Artemis’.