Fundamental study on the breeding of blue flowers due to copigments in Japanese garden. Iris ensata Thunb.

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The objective of the present study was to breed blue flowers of Iris ensata. Firstly, genetic analysis was carried out for methylation of delphinidin 3RGac5G.The result showed that methylation of delphinidin 3RGac5G was controlled by a dominant gene, which is symbolized as Mt.Secondly, the cause of bluing effect on the flower color of the bluish purple varieties in malvidin 3RGac5G-petunidin 3RGac5G type was clarified. No particular relationship between colors and pH of flowers among the malvidin 3RGac5G-petunidin 3RGac5G type varieties was recognized. Among these varieties, however, ther was a significant correlation (r=0.887^<**>) between the lambda max and the flavone contents. This suggests that the bluing effect on the flower color of the bluish purple varieties is depended upon the copigmentation between anthocyanins and flavones. Thirdly, the in vitro identification of copigmentation was carried out using anthocyanins, malvidin 3RGac5G,petunidin 3RGac5G and delphinidin 3RGac5G which are major pigments of I.ensata. These anthocyanins brought about copigmentation, i.e., bathochromic shift (bluing effect) of visible lambda max due to increased concentrations of isovitexin, and 32 to 35 nm were estimated as the magnitude (DELTA lambda max) of each shift. In addition, the absorption spectrum of 0.1mM malvidin 3RGac5G,0.07mM petunidin 3RGac5G and 0.7mM isovitexin mixture closely matched those of the fresh outer perianths of the bluish purple varieties, 'Suiten-isshoku', 'Hekikai' and 'Yakonotama' which belong to the malvidin 3RGac5G-petunidin 3RGac5G type of I.ensata. Therefore, these results indicate that the bluing effect on the flower color of the bluish purple varieties is caused by the copigmentation between these anthocyanins and isovitexin. Finally, the breeding strategy of blue flowers due to copigmentation of delphinidin 3RGac5G with isovitexin was discussed.