Plant having blue flower color and breeding method therefor

A method of creating a plant with a blue flower color, the method comprising the step of transforming the cells of the plant to express a Campanula-derived flavonoid 3′,5′-hydroxylase transgene (CamF3′5′H) and a Clitoria-derived anthocyanin 3′,5′-O-glucosyltransferase transgene (CtA3′5′GT) so that delphinidin-based anthocyanins having glycosyl-residues at both the 3′- and 5′-positions of the anthocyanin B-ring coexist with a flavone glycoside or flavonol glycoside in the cells of the plant,

• wherein the transformation is carried out by:
• introducing the Clitoria-derived anthocyanin 3′,5′-O-glucosyltransferase transgene into the cells of the plant;
• further introducing the Campanula-derived flavonoid 3′,5′-hydroxylase transgene into the cells of the plant when the cells of the plant do not accumulate any delphinidin-based anthocyanins;
• and
• further optionally introducing a flavone synthase transgene or a flavonol synthase transgene into the cells of the plant when the cells of the plant do not accumulate any flavone glycosides or flavonol glycosides,
• wherein the plant is rose, lily, carnation, dahlia, Phalaenopsis aphrodite, or chrysanthemum,
• wherein the delphinidin-based anthocyanins having glycosyl groups at both the 3′- and 5′-positions of the anthocyanin B-ring and the flavone glycoside or the flavonol glycoside coexist in a quantity ratio of 1:5 to 1:10, and wherein the intravacuolar pH in the cells of the plant is 5.2 to 6.4.