The Citrus Mutant Jedae-unshiu Induced by Gamma Irradiation Exhibits a Unique Fruit Shape and Increased Flavonoid Content

Satsuma mandarin (Citrus unshiu Marc. cv. Miyagawa-wase) is the most widely cultivated citrus variety in Korea. Although most varieties are imported from Japan, efforts have focused on developing new domestic varieties. We produced mutants by irradiating C. unshiu Marc. cv. Miyagawa-wase scions with gamma rays and grafting them onto C. unshiu Marc. cv. Miyagawa-wase branches. We compared the characteristics of these mutants with Miyagawa-wase fruit as a control. A mutant line named Jedae-unshiu with a unique fruit shape was selected for investigation in detail. The phenotype of Jedae-unshiu fruit demonstrated vertical troughs on the flavedo, smooth albedo without rough protruding fibers, and good adhesion between peel and flesh. In addition, Jedaeunshiu had thicker peels and higher fruit hardness than the control. Higher levels of hesperetin and narirutin, representative flavonoids, accumulated in the peel and flesh of Jedae-unshiu than those of the control. Cellular-level microscopic observations of the mature fruit peels demonstrated epidermal cell disruption in the control but not in Jedae-unshiu. Our results suggest that Jedae-unshiu has high possibility for development as a good storage variety containing large amounts of flavonoids, in addition to potential for ornamental value due to the unique shape of the fruit.