A research team led by Professor Emeritus Takuji Hoshino of Okayama University of Science (OUS) has successfully cultivated a new wine grape variety called “Muscat Shiragai.” The hybrid was produced by crossing the wild Shiraga grape, a species native only to the Takahashi River basin in Okayama Prefecture, with Muscat of Alexandria. The group has already submitted the new variety for registration with Japan’s Ministry of Agriculture, Forestry and Fisheries (MAFF), and the application has been formally accepted.
At a press event hosted by OUS, Professor 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.”
Inspiration From a Rare Wild Grape
Professor Hoshino, an expert in plant systematics, founded the Institute of Viticulture and Enology at OUS in April 2017. During his collaboration with Funao Winery in Kurashiki City, he became interested in the Shiraga grape, a rare and endangered wild species found only in specific parts of Okayama Prefecture. This discovery sparked the idea of developing an original, locally bred wine grape by combining Shiraga with Muscat of Alexandria.
To bring the idea to life, OUS signed a comprehensive partnership agreement in February 2018 with Kurashiki City and Funao Winery. The collaboration became part of a national initiative focused on regional revitalization and the “branding of local resources,” positioning the project as both a scientific and cultural effort.
By fiscal year 2022, the team had produced wines from several experimental breeding lines. Each was tested for sugar levels, acidity, pH, and overall taste. After years of refinement, the most promising strain was chosen, and “Muscat Shiragai” was officially established as a new variety in 2024.
The registration application was jointly submitted by Kake Educational Institution and Kurashiki City in December 2024 and was made public in June 2025. Full approval and registration are expected to be completed within the next four to five years.
A Warm Reception at the Press Conference
The press conference included key representatives such as Kurashiki Deputy Mayor Kenji Komatsu, Funao Winery CEO Kenichiro Miyake, and OUS President Hiroyuki Hirano. Attendees sampled both the Muscat Shiragai grapes and the wine made from them. The fruit was described as “sweet and very delicious,” while the wine impressed tasters with its “subtle Muscat aroma and smooth drinking quality.”
Deputy Mayor Komatsu expressed optimism: “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.”
CEO 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.”
President Hirano noted: “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.”
At present, 20 Muscat Shiragai vines are being cultivated at both Funao Winery and the OUS vineyard, producing 41.6 kilograms of grapes in 2024. In addition, 300 grafted vines were planted at the end of fiscal year 2023. The goal is to harvest more than 500 kilograms by 2028-2029. The research team is also refining vineyard management techniques, such as leaf removal, fertilization, and irrigation, to further enhance grape quality.
The Legacy of the Shiraga Grape
The Shiraga grape was first identified as a new species in 1918 by renowned botanist Tomitaro Makino. Its Japanese name honors Jukichi Shiraga, a botanist from Niimi City who discovered the plant. This wild grape is known for its naturally high sugar content, low acidity, and resistance to fruit cracking, as well as its tolerance to diseases such as black rot and ripe rot.
