Inbreeding, coancestry, and founding clones of apple cultivars released from Korea

Inbreeding and coancestry coefficients were calculated for 20 apple (Malus × domestica Borkh.) cultivars released from Korea using their recorded pedigree information. The overall mean inbreeding coefficient was 0. 034 for all 20 cultivars. Frequently used founding clones were 'Grimes Golden', 'Delicious', 'Ralls Janet', 'Earli Blaze', and 'Esopus Spitzenburg'. Coefficients of coancestry among all 20 cultivars and the above mentioned five founding clones averaged 0. 075, 0. 075, 0. 0075, 0. 069, and 0. 024, respectively. The average coancestry within the apple cultivars released from breeding program was 0. 136 and mean coefficient ranged from 0. 115 to 0. 166, which is comparable to 0. 125 for half-sib relationship. The redundant use of the same parents and their progenies can narrow the genetic base, thereby limiting genetic gain. Strategies are suggested for maintaining and increasing the genetic diversity, as well as for careful examining of pedigrees for future apple breeding in Korea.