Yamada Nishiki, long regarded as the premier rice variety for sake brewing and accounting for nearly 40% of Japan’s sake rice production, is facing mounting challenges linked to rising temperatures caused by climate change. Even in Hyogo Prefecture, the birthplace of Yamada Nishiki and home to many sake brewers, there are growing concerns about the future viability of this cultivar.
Hyogo produces about 30% of Japan’s sakamai, or sake rice, with most grains specially cultivated for brewing purposes. A key feature of sake rice is the shinpaku, a white starchy core essential for fermentation. Larger shinpaku cores generally translate to better brewing quality. However, Yamada Nishiki and other popular varieties such as Gohyakumangoku are increasingly affected by warmer summers, which negatively impact rice quality, yield, and brewing suitability.
Experts highlight that when average temperatures in the 20 days following flowering exceed roughly 27 degrees Celsius, rice quality declines. Heat during this critical grain filling stage results in smaller, less translucent grains and a reduced proportion of grains developing a desirable shinpaku core. More importantly, the starch within the shinpaku becomes less susceptible to enzymatic breakdown during fermentation, reducing the amount of fermentable sugar available to yeast and ultimately diminishing sake yield.
To address these issues, Hyogo Prefectural researchers developed Hyogo Sake 85 (HS85), a heat-tolerant rice variety created in 1986 by crossing Yamada Nishiki with a Korean strain selected for its short stalk, disease resistance, and high yield. Officially named in 2017, HS85 was first introduced commercially in 2018 by three designated Hyogo breweries, including the 12th-generation Yamana Shuzo in Tamba.
HS85 demonstrates greater resistance to heat-related damage compared to other regional varieties like Gohyakumangoku and Hyogo Kita Nishiki. It also offers strong resistance to blast fungal disease and improved lodging resistance due to its shorter stalks. Notably, HS85 produces compounds that contribute to the fruity aromas prized in ginjô-style sake. However, fermentation with HS85 tends to proceed faster, requiring brewers to carefully manage temperature control to maintain delicate flavor profiles.
Yamana Shuzo has incorporated HS85 as a standard variety, noting it yields sake with a richer, fuller body and crisper finish compared to Yamada Nishiki. The brewery has even replaced Hyogo Kita Nishiki entirely with HS85 for everyday sake products, citing cleaner flavor profiles and easier dissolution. Other breweries in the region, such as Kinoshita Brewery in Kyoto and Kamonoshō Shuzo in Tamba, have also adopted HS85, with the latter winning a platinum award at the 2025 Kura Master competition for a sake made with the variety.
Despite these benefits, HS85 remains limited in cultivation. As of July 2025, only 17 hectares nationwide were planted with HS85, compared to 4,697 hectares of Yamada Nishiki in Hyogo alone. Researchers attribute this disparity partly to Yamada Nishiki’s entrenched reputation and also challenges in scaling seed production for HS85.
In response to ongoing climate pressures, other regions are exploring heat-tolerant sake rice options. Hiroshima, for example, has begun promoting Moe Ibuki since 2023, while the Hokuriku region is developing varieties resistant to extreme heat.
Looking ahead, Hyogo researchers aim to build the HS85 brand and expand awareness among brewers and consumers, both domestically and internationally, collaborating with trade organizations and industry experts. Takuma Sugimoto of the Awaji Agricultural Technology Institute acknowledges the importance of evolving Yamada Nishiki’s genetics to better withstand warming conditions, envisioning a “Neo-Yamada Nishiki” that integrates enhanced heat resilience.
While Yamada Nishiki remains dominant, Japan’s sake industry is actively adapting to climate change by developing and adopting new rice varieties to secure the future of sake production.