‘Ruby Sweet’ is a new apple (Malus pumila Mill.) with pale-red flesh released by the National Agriculture and Food Research Organization (NARO) Institute of Fruit Tree and Tea Science (NIFTS) in Japan. ‘Ruby Sweet’ originated from a cross between the red-fleshed genotype ‘JP114069’ and ‘Fuji’ that was performed in 1993 at NIFTS, in Morioka, Japan. The tree was initially selected in 2008 based on its red flesh and good fruit quality. It was released as ‘Ruby Sweet’ and registered as No. 24268 under the Plant Variety and Seedling Act of Japan in 2015.
The fruit of ‘Ruby Sweet’ ripens in mid-October in Morioka. The fruit shape is globose to short- globose. It has a mean fruit weight of about 470 g, which is more than 200 g larger than ‘Jonathan’. The skin is red at harvest with stripes. The texture of the flesh is medium-crisp, superior to that of ‘Pink Pearl’. The fruit is moderately juicy, with a mean soluble solids content of 14.7% (significantly higher than that of ‘Pink Pearl’ [12.2 %]) and a titratable acidity of 0.36 g/100 mL (significantly lower than those in ‘Pink Pearl’ [1.20 g/100 mL] and ‘Jonathan’ [0.87 g/100 mL]).
The tree is spreading shape, with medium vigor when grafted on JM7 rootstock, and it blooms 3 day earlier than ‘Jonathan’. Since its S-genotype is S3S9, ‘Ruby Sweet’ is cross-incompatible with ‘Jonagold’ (S2S3S9), but is cross-compatible with other major commercial cultivars such as ‘Fuji’ (S1S9) and ‘Tsugaru’ (S3S7). The resistance level of ‘Ruby Sweet’ to Alternaria leaf spot is resistant to moderately susceptible.