A new red butterhead lettuce (Lactuca sativa L.) with transverse broad elliptic, red leaves, ‘Sun Red Butter’, with late bolting and high yield, was developed from a cross between ‘Jajusangchu’ (red leaf color and half crisp) and ‘Dukseomjeokchukmyeon’ (high yield). The crossing and selection for advanced lines was previously carried out using the pedigree method during the period 2001–2009. The advanced lines were evaluated for yield and adaptability at several locations in Korea (Gangwon-do, Gyeonggi-do, Chungcheongbuk-do, Jeollabuk-do, Gyeongsangnam-do, and Jeju-do) in 2011. The type of matured stage is early and medium butterhead lettuce. The shelf life of ‘Sun Red Butter’ was four weeks longer than that of ‘Germania’ at 4°C. The anthocyanin content of ‘Sun Red Butter’ was lower than that of ‘Germania’ at 11.2 mg/100 g. The BSL (latucin+8-deoxylactucin+lactucopicrin) content of ‘Sun Red Butter’ was higher than that of ‘Germania’ at 32.8 µg/g, DW. The marketable yield of ‘Sun Red Butter’ was higher than that of ‘Germania’ by 67% (at 621.4 g per plant), and ‘Sun Red Butter’ showed a particularly improved yield under high-temperature cultivation in the field. Furthermore, ‘Sun Red Butter’ had better taste characteristics and was crisper and sweeter than ‘Germania’. Therefore, we recommend that the new cultivar ‘Sun Red Butter’ would be suitable for cultivation in spring and fall. Furthermore, this new cultivar could be harvested in a single harvest, as in a head lettuce, and could therefore be managed more efficiently and economically by farmers.

A new lettuce (Lactuca sativa L.) variety ‘Sunny Red Butter’ that belongs to butter-head type has transverse broad elliptical leaf with red color. Crossbreeding of ‘Oriana’ and ‘Cardinale’ was made to obtain seeds of the F1 generation. Subsequent generations were selected using in pedigree methods until 2011, resulting in ‘Sunny Red Butter’. The new variety ‘Sunny Red Butter’ is brown in seeds and the upper part of the leaf is light red and glossy. The leaf stalk is white. It can be harvested from 30 days after planting. The average harvested leaf number is 51 leaves per plant. The average weight is 556.5g per plant, which is 44% higher than a control lettuce variety ‘Germania’. It showed that 30.9 tons/ha production was made in spring, summer, and autumn cultivations for 3 years in 6 areas (Daegwanryeong, Gyeonggi, Chungbuk, Jeonbuk, Gyeongnam, and Jeju) than the control variety ‘Germania’. The shelf-life of ‘Sunny Red Butter’ was 4 weeks for storage at 4℃. Anthocyanin amount (10.3 mg/100g) of ‘Sunny Red Butter’ was lower than that of ‘Germania’. BSL (latucin+8-deoxylactucin+lactucopicrin) amount of ‘Sunny Red Butter’, the bitter ingredients was 26.1 μg/g and higher than BSL amount of ‘Germania’. Leaf hardness of ‘Sunny Red Butter’ was 1,554 kg/cm 2 , which was thicker than ‘Germania’. ‘Sunny Red Butter’ showed better taste (more crispy and sweeter) than ‘Germania’. The new variety ‘Sunny Red Butter’ can be used as lettuce productions during spring and autumn in most area and in summer in highland of Korea.