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Tonewase
Parents: Norin No.8 (seed parent) and Norin No.1 (pollen parent). Crossed in 1940. Bred by Konosu Testing Site (cross) → Tamai Branch, Saitama Prefectural Agricultural Experiment Station (selection).
Kanto No.41 KAN0000410
Pedigree
Skip the diagram and read the listParents
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Norin No.8 seed parent
Kinki No.15 ・ Late-maturing within the early group; fairly strong blast resistance; medium, slightly long grain; high yield and good quality
Sources: イネ品種データベース検索システム「関東41号（トネワセ）」品種来歴文書
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Norin No.1 pollen parent
Hokuriku No.4 ・ High yielding with good grain quality and eating quality; susceptible to rice blast
Sources: イネ品種データベース検索システム「関東41号（トネワセ）」品種来歴文書
Descendants
Relations are counted along the shortest line of descent. The rows in the diagram follow the order of crosses, so a variety with more than one path down can sit lower in the diagram than its relation here suggests.
Koshihikari's grandmother crossed with its father
"Kanto No.41" was crossed in 1940 at the Konosu Testing Site of the Ministry of Agriculture and Forestry Agricultural Experiment Station, taking "Norin No.8" as the mother and "Norin No.1" as the father; in 1943 the Tamai Branch of the Saitama Prefectural Agricultural Experiment Station received the F3 seed as test material for the Ministry's designated paddy rice breeding trial, and has selected and fixed it since.
The mother is Norin No.8, the father Norin No.1.
Norin No.8 is Koshihikari's maternal grandmother, and Norin No.1 is Koshihikari's father. Tonewase is those two crossed together.
Koshihikari is the child of Norin No.22 (a child of Norin No.8) and Norin No.1, so Tonewase stands to Koshihikari as half sibling and half aunt at once.
The cross was made in 1940, four years before Koshihikari's.
Especially strong against bacterial leaf blight
"Kanto No.41" is an early non-glutinous variety ripening slightly later than "Norin No.1", with especially strong resistance to bacterial leaf blight. Its habit is intermediate, its panicles extremely long compared with "Norin No.1", its grain also relatively large, and its productivity high.
What it was strong against was not blast but bacterial leaf blight.
The same pair of parents produced Koshihikari; this one came out strong against a different disease. Crossing the same two varieties gives different results depending on what the person selecting was watching for.
Destined for "special low-lying wetland"
This line is judged well suited to the special low-lying wetlands where "Norin No.1" had spread, and particularly to the relatively thin-soiled parts of those districts.
Of the land Norin No.1 occupied, it takes the low, wet, thin-soiled part.
Ibaraki and Shizuoka asked for it as a recommended variety from 1960. As with Ishikawa on the page for everything from the same cross as Koshihikari, prefectures were assigning varieties by the character of the land.
Sources disagree
How the seed parent of Norin No.1 is written
- Moritawase, written 森多早生 — イネ品種データベース検索システム 交配系譜図「北陸4号」
- Moritawase, written 森田早稲 — イネ品種データベース検索システム「北陸4号（水稲農林1号）」品種来歴文書
The two spellings appear in the same NARO database, in the pedigree field and in the historical document respectively. We use the pedigree field's spelling and list the other.
How Kamenoo No.4 is written
- 亀の尾4号 — イネ品種データベース検索システム 交配系譜図「陸羽132号」
- 亀ノ尾4号 (the common spelling)
We follow the NARO database. The commonly seen spelling uses a katakana no; we prefer the spelling we can cite.
On naming
Variety names are proper nouns. We use a name in this language only where a published source for it can be cited; otherwise the Japanese name stands.
What we have not yet confirmed
We have not looked below the top twenty
The site covers the twenty most widely planted varieties of the 2024 crop and the varieties that connect them back to Koshihikari. Many descendants exist below that line; we have not yet verified them against primary sources.
The year Masshigura was crossed
Neither Aomori Prefecture's table of recommended-variety characteristics nor the NARO database gives the year Masshigura (Aokei No.138) was crossed. The cross itself, Ou No.341 / Yamagata No.40, and its adoption as a recommended variety in fiscal 2004 are confirmed from primary sources; the year of the cross is not. For the same reason we do not say which parent was the seed parent. On 8 October 2026 we went back to the breeder's own side. The Masshigura page in the variety database of the Aomori Prefectural Industrial Technology Research Center's Agriculture and Forestry Research Institute carries a heading reading “The origin of Masshigura” — with nothing under it. Of the institute's bulletins, only No.42 (2015) onward are online, and the issue that would hold the breeding report for Masshigura is not among them. So the year of the cross is absent from the breeder's own published material as well.
Sources
The source document is in Japanese.
- イネ品種データベース検索システム 交配系譜図「越南17号」 — Institute of Crop Science, NARO ・ primary source ・ accessed 2026-09-10
- イネ品種データベース検索システム「北陸4号（水稲農林1号）」品種来歴文書 — Institute of Crop Science, NARO ・ primary source ・ accessed 2026-09-10
- イネ品種データベース検索システム 交配系譜図「北陸4号」 — Institute of Crop Science, NARO ・ primary source ・ accessed 2026-09-10
- イネ品種データベース検索システム「北陸4号を親とする品種一覧」（全263行） — Institute of Crop Science, NARO ・ primary source ・ accessed 2026-10-01
- イネ品種データベース検索システム 交配系譜図「近畿34号（水稲農林22号）」 — Institute of Crop Science, NARO ・ primary source ・ accessed 2026-10-01
- イネ品種データベース検索システム 交配系譜図「近畿15号（水稲農林8号）」 — Institute of Crop Science, NARO ・ primary source ・ accessed 2026-09-10
- イネ品種データベース検索システム 交配系譜図「陸羽132号」 — Institute of Crop Science, NARO ・ primary source ・ accessed 2026-09-10
- イネ品種データベース検索システム 交配系譜図「陸羽20号」 — Institute of Crop Science, NARO ・ primary source ・ accessed 2026-09-10
- コシヒカリのエピソード1 〜交配から系統の育成まで〜 — Niigata Prefectural Government ・ primary source ・ accessed 2026-09-10
- イネ品種データベース検索システム「近畿15号（水稲農林8号）」品種来歴文書 — Institute of Crop Science, NARO ・ primary source ・ accessed 2026-09-16
- イネ品種データベース検索システム「関東41号（トネワセ）」品種来歴文書 — Institute of Crop Science, NARO ・ primary source ・ accessed 2026-10-01