A team from Okayama University of Science has developed a new wine grape variety, Muscat Shiragai, by crossing a rare wild Shiraga grape with Muscat of Alexandria. This hybrid aims to boost regional revitalization through unique local wine production. The variety has been submitted for official registration in Japan.
Led by Professor Emeritus Takuji Hoshino, researchers at Okayama University of Science (OUS) crossed the endangered Shiraga grape, native only to the Takahashi River basin in Okayama Prefecture, with the Muscat of Alexandria to create Muscat Shiragai. Hoshino, an expert in plant systematics, founded the Institute of Viticulture and Enology at OUS in April 2017. His interest in Shiraga grew during collaboration with Funao Winery in Kurashiki City, leading to a partnership agreement in February 2018 with the city and the winery. This effort aligns with a national initiative for regional revitalization and branding local resources.
By fiscal year 2022, the team produced experimental wines, testing them for sugar levels, acidity, pH, and taste. The promising strain was selected, officially establishing Muscat Shiragai in 2024. Kake Educational Institution and Kurashiki City jointly submitted the registration application to Japan's Ministry of Agriculture, Forestry and Fisheries in December 2024, which became public in June 2025. Full approval is anticipated within four to five years.
At a recent press conference, attendees sampled the grapes, described as "sweet and very delicious," and the wine, noted for its "subtle Muscat aroma and smooth drinking quality." Hoshino shared his vision: "I wanted to create a wine grape that incorporates wild genetic traits. If this grape becomes widely cultivated and its wine contributes to regional revitalization and tourism, that would be the best outcome."
Kurashiki Deputy Mayor Kenji Komatsu expressed enthusiasm: "We are very much looking forward to offering a wine filled with the unique charm that can only be produced in Kurashiki. We also anticipate further research results to refine Muscat Shiragai into an even more sophisticated grape." Funao Winery CEO Kenichiro Miyake added: "With Muscat Shiragai as a branded grape, we hope to create a new high-value red wine identified with Kurashiki as its place of origin. Please look forward to the day when we can bring this to market."
OUS President Hiroyuki Hirano emphasized collaboration: "Collaboration among industry, academia, and government is essential for building innovative local communities. OUS will continue integrating education and research, returning the results to the community, and contributing to solving regional and social issues."
Currently, 20 vines at Funao Winery and OUS produced 41.6 kilograms in 2024. An additional 300 grafted vines were planted at the end of fiscal year 2023, with a goal of over 500 kilograms by 2028-2029. The team is optimizing techniques like leaf removal, fertilization, and irrigation. The Shiraga grape, identified as a new species in 1918 by Tomitaro Makino and named after botanist Jukichi Shiraga, offers high sugar content, low acidity, resistance to fruit cracking, and tolerance to diseases such as black rot and ripe rot.