NEW JAPANESE PEAR CULTIVAR 'YOUSUI'

Abstract

'Yousui' is a new late maturing, russet-skin type cultivar of Japanese pear, released by the Aichi-ken Agricultural Research Center. This cultivar originated from a cross between 'Niitaka' and 'Kousui' made in 1990. In 2001, 'Yousui' was registered on March 13 under the Seeds and Seedlings Law of Japan. 'Yousui' trees are as vigorous as 'Niitaka' and twigs are thick. The tree form looks like that of 'Niitaka'. The tree exhibits few axillary flower buds on shoot as 'Kousui', but it is easy to maintain flower buds on spurs. It is considered that 'Yousui' is fairly productive as 'Niitaka'. It blooms at the same time as 'Housui', 3 to 4 days later than 'Niitaka'. 'Yousui' is cross-compatible with 'Kousui', 'Housui' and 'Niitaka'. It has large quantities of pollen. 'Yousui' matures between ‘Housui’ and 'Niitaka', late September to early October in Aichi prefecture. Fruit is oblate in shape and the skin is yellowish brown at maturity. Fruit is very large like that of 'Niitaka', about 900g. The flesh is white, soft, juicy and crisp. It is considered superior to 'Niitaka' in these points. Brix values are 14 to 15% in a usual year, 0.5 to 1% higher than 'Niitaka'. pH values are 5.2 to 5.3, less acid than 'Niitaka'. The shelf life is shorter than those of other late maturing cultivars such as 'Niitaka' and 'Shinsei'. The fruit quality remains good for about 15 days when the fruit is kept at room temperature (about 15°C). ‘Yousui’ is resistant to black spot disease (Alternaria alternata Japanese pear pathotype) and pear necrotic spot virus. 'Yousui' may be tolerant to other diseases and insect pests under standard cultivation condition. Furthermore, as for ‘Yousui’, a physiological disorder is not being observed at present.