Kyoto sake rice: Iwai


There are two varieties of Kyoto-based rice suitable for making sake: Iwai (sake specific rice) and Kyo-no-kagayaki (sake rice).

Kyoto Prefectural Agriculture, Forestry and Fisheries Technology Center Manage, Mr Tetsuya Ashida, and Chief Researcher Mr Toshiyuki Osako were kind enough to grant Sake Experience Japan with an interview. We asked them about the development of Kyo-no-kagayaki and revival of the legendary Iwai.


Kyoto Prefectural Agriculture, Forestry and Fisheries Technology Center’s Agriculture Experiment Center started cultivating rice in 1915. They used the “pure line selection method” to selectively propagate potential rice varieties of both Kyoto and non-Kyoto rice. In 1929, the Center started examining the Nojoho variety of rice. After four years, Iwai was “born” and was listed as “recommended varietyin Kyoto.

Despite Iwai’s high suitability for sake production, it has faced several twists and turns in terms of being listed as “recommended variety”. The production area had increased to 646 hectares by 1936 but the World War II food shortages meant a reprioritisation of eating rice and the crop acreage dropped dramatically. In 1946, Iwai was dropped from the recommended variety list and Kyoto prefecture lost any obligation to supply Iwai seed to farmers. Delisting didn’t completely eradicate the crop, but it was apparent that the variety deteriorated.

Since Iwai was delisted as a recommended rice in 1946, calls have been growing louder for its revival because of higher sake production suitability than other recommended varieties. And, of course, food shortages are no longer a concern. In 1955 it was relisted and in 1962, the crop acreage reached 396 hectares. However it faced delisting again in 1973 because its height was unsuitable for the harvest machines most common at the time. In addition, it loses the grains too easily even prior to threshing, so popularity declined and it was delisted again in 1973. 

Almost twenty years later, the desire to produce Kyoto-origin sake emerged among sake breweries and the second revival of Iwai was completed in 1992. However Kyoto Prefectual Agricultural Research Institute no longer held the rice seed so these were provided by Kyoto Prefectural University.  At the same time of this revival project, research commenced to reduce the plant height from up to 1.2m (compared with the 70cm of the most famous food rice, koshihikari) and achieve heavier senryujyu for better yield. Since 1999, one particular strain has been selected from 18,200 potential candidates as the ideal variety of Iwai. It has a lower height of 1-1.1m and heavier senryujyu than the original.


The perfected Iwai has a similar sake production suitability as the “king “of sake specific rice, Yamadanishiki however it still poses difficulties as a sake specific rice, such as the lower yield of 34kg per acre (compared with food rice Koshihikari’s 50kg per acre) and higher water absorption (higher than Yamadanishiki), requiring more careful production.. 

The Research Department at Kyoto Municipal Institute of Industrial Technology and Culture (KMIITC) has become a center of the project to identify the relationship between rice and sake production methods, with a view to (for example) identifying a scientific link between sake aroma and the rice growing method. We strongly believe that the re-revived Iwai will play an important role in enhancing the potential of Kyoto sake.

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