A new lettuce (Lactuca sativa L.) with elliptic and dark green leaves, ‘Sambokhacheong’, which is tolerant to tipburn with good yield, was developed from a cross between ‘Meokchima’ (dark red leaves) and ‘Yeoreumcheongchima’ (high yield, green leaves). The crossing and selection for advanced lines was conducted by the pedigree method in 2006-2012. The advanced lines were evaluated for yield and adaptability at several locations in Korea (Gangwon-do, Gyeonggi-do, Chungcheongbuk-do, Chungcheongnam-do, Jeollabuk-do, Gyeongnam-do, and Jeju-do) over three years starting from 2015. The evaluations revealed that this lettuce was early- and medium-maturing leaf lettuce, with a shelf-life of four weeks at 4 ℃, longer than that of ‘Yeoreumcheongchima’. ‘Sambokhacheong’ showed no symptoms of tipburn during hot seasons in the southern parts of South Korea compared ‘Yeoreumcheongchima’. The content of bitter sesquiterpene lactones (latucin, latucin+8-deoxylactucin+lactucopicrin) of ‘Sambokhacheong’ at 57.16 (μg/g, dry weight) was higher than that of ‘Yeoreumcheongchima’. Compared with ‘Yeoreumcheongchima’, the marketable yield of ‘Sambokhacheong’ was 2% higher (at 551 g per plant) and showed late bolting at 111 days after sowing in the summer cultivation season. Its leaves are better, crispier, and sweeter than those of ‘Yeoreumcheongchima’. Therefore, we recommend the new cultivar ‘Sambokhacheong’ for cultivation in hot seasons (Registration No. 6915).

A cultivar of lettuce (Lactuca sativa L.) with sharply large oval and purple leaf, ‘Jahokmaschima’, which has late bolting and a high yield, was developed from a cross between ‘Bulkkoch’ (dark red leaf color and early bolting) and ‘Cheongpung’ (high yield). The cross and selection for advanced lines was conducted by the pedigree method between 2005 and 2011. The advanced lines were evaluated for yield and adaptability at six locations in Korea (Gangwon-do, Gyeonggi-do, Chungcheongbuk-do, Jeollabuk-do, Gyeongnam-do, and Jeju-do) for 3 years until 2014. The ‘Jahokmaschima’ lettuce has a gray seed color, and the leaf type of the matured stage is a large oval leaf, leaf no. 67 per plant, and late bolting. In particular, the ‘Jahokmaschima’ has good resistant to tip burn in the growth period. The anthocyanin and vitamin C content of ‘Jahokmaschima’ were lower than those of ‘Tomallin’, at 4.05 mg/100g and 27.7 mg/100g, respectively. The BSL (bitter sesquiterpene lactones; latucin, 8-deoxylactucin, and lactucopicrin) content of ‘Jahokmaschima’ was lower than that of ‘Tomallin’, at 2.120 µg/g DW. Compared with ‘Tomallin’, the marketable yield of ‘Jahokmaschima’ was 1% higher (at 374 g per plant) and particularly improved late in bolting in high temperature cultivation in the field. The shelf-life of ‘Jahokmaschima’ was similar to ‘Tomallin’ at 4ºC. Furthermore, it tasted better, and was crispier and sweeter than ‘Tomallin’. Thus, we recommend that the new cultivar ‘Jahokmaschima’ is suitable for cultivation in spring and fall.

‘Hyesun’, a new cultivar of leaf lettuce (Lactuca sativa L.) with sharply wrinkled oval and red leaf, produced by a cross between 'Nongjeockchima’ (red leaf color) and ‘Jeockchima’ (high yield) has late bolting and high yield in the field. The cross and selection for advanced lines had been done by the pedigree method from 2002 to 2008. The ‘Hyesun’ has gray seed color and medium elliptic leaves. The yield and adaptability of the advanced lines were evaluated at several locations of Korea (Gangwon-do, Gyeonggi-do, Chungcheongbuk-do, Jeollabuk-do, Gyeongnam-do, and Jeju-do) for 3 years (from 2009 to 2012). The type of maturity of ‘Hyesun’ is early-medium. The leaf hardness of ‘Hyesun’ is a 1,237kg/cm², which is not thicker than ‘Yeolpungeokchima’. The anthocyanin content of 'Hyesun' is a 88.32mg/100g, which is lower than that of ‘Yeolpungeockchima’. The BSL (Bitter Sesquiterpene Lactones, latucin + 8-deoxylactucin + lactucopicrin) content of ‘Hyesun’ is a 5.0ug/g of DW, which is lower than that of ‘Yeolpungeockchima’. Compared to ‘Yeolpungeockchima’, marketable yield of ‘Hyesun’ was higher by 7% (at 381g per plant) and the bolting time of ‘Hyesun’ was remarkably delayed under high temperature cultivation in the field. The shelf-life of ‘Hyesun’ was four weeks longer than ‘Yeolpungeockchima’ at 4°C. Furthermore, because ‘Hyesun’ is more crispy and sweeter than ‘Yeolpungeockchima’, ‘Hyesun’ has the better taste. So, we recommend that the new cultivar ‘Hyesun’ can be suitable for cultivation in both spring and fall season.

A new lettuce cultivar ‘Misun’ (Lactuca sativa L.) with wrinkled traverse narrow elliptic and deep red leaf, which has late bolting and high yield. It was developed from a cross between ‘Yeoreum Jeocgchima’ (deep red leaf color) and ‘Yeoreum dukseomjeokchukmyeon’ (high yield). The cross and selection for advanced lines had been done by the pedigree method from 2001 to 2008. The advanced lines were evaluated for yield and adaptability at several locations in Korea (Gangwon-do, Gyeonggi-do, Chungcheongbuk-do, Jeollabuk-do, Gyeongnam-do, and Jeju-do) from 2009 to 2011 year. The ‘Misun’ has gray seed color and traverse narrow elliptic leaves. The shelf-life of ‘Misun’ was four weeks longer than ‘Dukseomjeokchukmyeon’ at 4°C. The anthocyanin content of ‘Misun’ (88.32 mg/100 g) was higher than that of ‘Dukseomjeokchukmyeon’(74.78 mg/100g). The BSL (latucin+8-deoxylactucin+lactucopicrin) content of ‘Misun’ (5.0 ug/g, DW) is lower than that of ‘Dukseomjeokchukmyeon’ (12.0 ug/g, DW). Compared to ‘Dukseomjeokchukmyeon’, marketable yield of ‘Misun’(289 g per plant) was 11% higher than that of it, showed good yield in fall season cultivation and has particularly improved expression of red leaf color at high temperature cultivation in the field. Furthermore, its taste is better, more crispy, and sweeter than those of ‘Dukseomjeokchukmyeon’. Thus, this new cultivar ‘Misun’ can be suitable for cultivation in low temperature during spring and fall season season.