Amanatsu Sour Orange

Amanatsu, also called Kawano Natsudaidai, is a bud-sport selection of Natsudaidai. The name here refers to the historical Kawano selection; it does not equate that cultivar with the separately documented UCR seedling CRC 3235.^{⁠[2]⁠[10]}

General profiles describe a broad, slightly flattened fruit with a thick, fragrant rind. Kankitsu Labo describes bright-orange peel and juicy flesh, while RyuKoch describes a coarse peel and variable seediness. Their size estimates and season descriptions differ: Kankitsu gives 70–100 mm and February–April harvest, while RyuKoch gives 10–12 cm and late spring to early summer. These are general profiles without an identified accession or measured sample.^⁠[6]⁠[5]

Skandiberg reported 11°Brix in one received fruit labelled Amanatsu and estimated more than 2 dL of juice from a separate later fruit. A follow-up says membranes nearly disappeared during juicing, while the earlier received-fruit report described tough membranes. The orchard and accession are unknown; the follow-up is not counted as a third measured fruit.^{⁠[3]⁠[4]⁠[7]}

Hodgson’s 1967 account places the Kawano limb sport in an Oita orchard around 1905 and says it was named and registered in 1950. RyuKoch instead gives discovery in Tsukumi, Oita, in 1935, citing Wikipedia. The discovery chronology remains unresolved; 1950 is the naming and registration date in Hodgson’s account.^⁠[2]⁠[5]

UCR’s CRC 3235 page records an open-pollinated seedling received as seed in 1957. Its later notes question the accession’s identity. Its necked fruit, seasonal descriptions and other accession traits are excluded from Amanatsu’s trait fields. The page’s reproduced 1986 report of 1–2% acid concerns the named Kawano account; it does not establish a measured CRC 3235 result or a pH value.^⁠[1]

Murai and colleagues studied flower-bud formation in material named Kawano Natsudaidai. Their 1989 abstract reports formation from early November to early February and differences in leaf and bark protein between bearing and non-bearing shoots. In their treatment experiment, GA₃ at 250 ppm inhibited next-season flower set, while BA at 300 ppm had little effect. The accession and field setting are not established by the reviewed English abstract.^⁠[8]

A 2021 study used fungus-inoculated pericarp labelled Kawano-natsudaidai to test plasma disinfection. Its reported D value of 1.88 minutes describes the treatment time for a 90% reduction in viable fungal cells under that laboratory setup. It is a postharvest surface-treatment result, not evidence of inherent disease resistance or ordinary storage performance.^⁠[9]