Accumulation of anthocyanin in apples in response to blue light at 450 nm: recommendations for producing quality fruit color under global warming

New apple (Malus domestica Soria) cultivars that can accumulate anthocyanin under nondirective visible light (without UV) and high temperatures will produce apples of good color under global warming conditions. However, how cultivars respond to visible light in terms of anthocyanin production and the role visible light plays in red color development have yet to be thoroughly studied. Accordingly, this study determined the effect of blue light on anthocyanin accumulation in two apple cultivars, 'Jonathan' and 'Fuji, under different temperatures. The results show that blue light of around 450 nm was most effective on anthocyanin accumulation in 'Jonathan' apples. This cultivar produced high amounts of anthocyanin and developed a dark red color under light-emitting diode (LED) blue light at 450 nm at temperatures between 15 degrees -25 degrees C. Even under temperatures as high as 30 degrees C, blue light stimulated anthocyanin production, while its amount was low. These results suggest that this cultivar's trait of responding to blue light at 450 nm could play a regulatory role in developing red color under nondirective visible light conditions, leading to the hypothesis that it may be possible to select new cultivars that easily develop red color under conditions of global warming.