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A research group led by Professor Emeritus Takuji Hoshino of Okayama University of Science (OUS) has successfully developed a new wine grape variety named "Muscat Shiragai," created by crossing the wild species Shiraga grape—native only to the Takahashi River basin in Okayama Prefecture—with Muscat of Alexandria. The group has filed for new variety registration with Japan's Ministry of Agriculture, Forestry and Fisheries (MAFF), and the application was formally accepted.

At a press conference held on July 4 at OUS, Professor Emeritus Hoshino stated, "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."

Professor Hoshino specializes in plant systematics. In April 2017, he became the founding director of the Institute of Viticulture and Enology at OUS. While collaborating with representatives of Funao Winery in Kurashiki City, he turned his attention to the Shiraga grape, a rare and endangered wild species found only in limited areas of Okayama Prefecture.

This inspired the idea of creating a uniquely "Okayama-born" wine grape by hybridizing it with Muscat of Alexandria. In February 2018, OUS signed a comprehensive cooperation agreement with Kurashiki City and Funao Winery, launching the project as part of a national government–recognized regional revitalization initiative to promote "branding of local resources."

By fiscal year 2022, wines were being brewed from different breeding lines and evaluated for sugar content, acidity, pH, and taste, leading to the selection of promising strains. Drawing on these trial results, the new "Muscat Shiragai" variety was finalized in 2024. The official application for new variety registration was jointly filed by Kake Educational Institution and Kurashiki City in December 2024 and was publicly announced in June 2025. The official registration is expected within four to five years.

The press conference, held at the Presentation Room in OUS Building A1, was attended by Kurashiki Deputy Mayor Kenji Komatsu, Funao Winery CEO Kenichiro Miyake, and OUS President Hiroyuki Hirano. Participants sampled the Muscat Shiragai grapes and wine, which were well received—described as "sweet and very delicious" for the fruit, and "with a subtle Muscat aroma and smooth drinking quality" for the wine.

Deputy Mayor Komatsu commented, "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."

Currently, 20 vines are cultivated at Funao Winery and the OUS vineyard, yielding 41.6 kilograms in 2024. An additional 300 grafted vines were planted at the end of fiscal year 2023, with a goal of harvesting more than 500 kilograms by 2028–2029. The team also plans to optimize practices such as leaf removal, fertilization, and irrigation to further improve quality.

The Shiraga grape was first described as a new species in 1918 by botanist Tomitaro Makino. Its Japanese name derives from Jukichi Shiraga, a botanist from Niimi City who discovered it. The species is known for its high sugar content, low acidity, resistance to fruit cracking, and tolerance to black rot and ripe rot.