Accumulation of carotenoids in a novel citrus cultivar 'Seinannohikari' during the fruit maturation

In the present study, carotenoid metabolism was investigated in the fruits of a novel citrus cultivar, 'Seinannohikari' (Citrus spp.). During the maturation, β,β-xanthophylls were accumulated rapidly with β-cryptoxanthin being the dominant carotenoid compound in the flavedo and juice sacs of 'Seinannohikari'. In the juice sacs of mature fruits, 'Seinannohikari' accumulated high amount of carotenoids, especially β-cryptoxanthin. The content of β-cryptoxanthin in the juice sacs of 'Seinannohikari' was approximately 2.5 times of that in 'Miyagawa-wase' (Citrus unshiu), which is one of its parental cultivars, at the mature stage. Gene expression results showed that the massive accumulation of β-cryptoxanthin might be attributed to the higher expression of carotenoid biosynthetic genes (CitPSY, CitPDS, CitZDS, CitLCYb2, CitHYb, and CitZEP), and lower expression of carotenoid catabolic genes (CitNCED2 and CitNCED3) in the juice sacs of 'Seinannohikari'.