New Citrus Cultivar ‘Asumi’

Abstract

‘Asumi’ is a new citrus cultivar that was released by the Okitsu Citrus Research Station, National Institute of Fruit Tree Science (presently the Division of Citrus Research, Institute of Fruit Tree and Tea Science), National Agriculture and Research Organization. ‘Asumi’ originated from a cross between ‘Kankitsu Okitsu No.46’ [‘Sweet spring’ (Citrus unshiu × C. hassaku) × ‘Trovita’ orange (C. sinensis)] as seed parent and ‘Harumi’ [‘Kiyomi’ (C. sp.) × Ponkan F-2432 (C. reticulata)] as pollen parent. From 2003, ‘Asumi’was designated Kankitsu Okitsu No.58, and it was included in the ninth citrus selection national trial, which was conducted at 28 prefectural experimental stations and two sites of the National Institute of Fruit Tree Research Station (Okitsu and Kuchinotsu) in Japan. In 2011, it was agreed that Kankitsu Okitsu No.58 was a suitable candidate for a new citrus cultivar. The cultivar was released as ‘Asumi’ in 2012 and was registered as No. 23723 under the Plant Variety Protection and Seed Act of Japan on September 30, 2014. The tree has medium vigor, and its shape is between spreading and upright. Long thorns develop on the branches and the leaves are spindle shaped. ‘Asumi’ is susceptible to citrus canker but not to citrus scab. Alternate bearing of ‘Asumi’ is medium, and preharvest drop of fruit is almost nonexistent. Occurrence of stem pitting caused by the citrus tristeza virus is moderate. The fruit weighs about 170 g and has a compressed shape. Skin color is orange with about 2.3 mm thickness and has smooth surface. Peeling is moderately difficult. The soluble solids content and acidity in the ripe fruit are about 15% and 1.15 g/100 mL, respectively. The fruit contains a few seeds, averaging about 1.5 seeds/fruit. The fruit ripens in early February in Shimizu, Shizuoka, Japan. Since the ripening and harvesting periods are mainly in early February, it is desirable to cultivate the tree in area with relatively warm winters to avoid cold damage. In addition, since ‘Asumi’ has weak resistance against citrus canker, in order to prevent damage, it is recommended to cultivate it in a greenhouse. If cultivated in open fields, it is desirable to select fields that are not exposed to strong winds and to plant windbreak trees around the fields.