Breeding of a new Japanese apricot (Prunus mume Siebold et Zucc.) cultivar 'Okjoo' with high yields.

Japanese apricot (Prunus mume Siebold and Zucc.) is a deciduous tree of the family Rosaceae, and it has long been used as a folk remedy for cough and dyspepsia. A new cultivar 'Okjoo' was developed from a cross between 'Gyokuei' and 'Rinsyu' carried out at the National Institute of Horticultural & Herbal Science in 1993. It was selected for good shape, large size and high yield capacity in 2006, and then it was granted official patent No. 4556 in 2013. It blooms 4 days and 2 days earlier than 'Gyokuer and `Rinsyu', respectively. Its flower petal color is pink, and the pollen amount is negligible. Its S-genotype, determined using Polymerase Chain Reaction with a S-RNase gene-specific primer pair, is S3S6. The average optimum harvest time of 'Okjoo' is late June. The fruit is 'round in shape and its suture is shallow. Average fruit weight is 18.5 g and it contains total soluble solids 7.66 Brix and titratable acidity at 4.81%. Fmk skin color is green. Sometimes only the light side of the fruits seems to develop blush. The incidence levels of scab (Cladosporium carpophilum Thumen) and bacterial shot hole (Xanthomonas arboricola pv. Pruni) are quite low. Consequently, 'Okjoo' seems to be a promising new cultivar for Japanese apricot growers.