New Hybrid Grape ‘Muscat Shiragai’ Debuts in Japan

A team of researchers at the Okayama University of Science has unveiled a novel wine grape variety known as Muscat Shiragai, marking a milestone in hybrid viticulture. The new cultivar pairs the wild Shiraga grape native to the Takahashi River basin in Okayama Prefecture with the globally recognised Muscat of Alexandria. The project was led by Professor Emeritus Takuji Hoshino, a plant systematics expert and founding director of the university’s Institute of Viticulture and Enology.

The wild Shiraga grape is valued for its high sugar content, low acidity and resilience against key vine threats such as black rot and ripe rot, as well as its tolerance to fruit-cracking. These traits made it an ideal candidate to merge with the aromatic profile of Muscat grapes. The collaboration extended to municipal and industry partners—including Funao Winery and the Kurashiki municipality—which signed a regional revitalisation agreement with OUS in early 2018 to support the development of a locally-branded grape variety.

During the 2024 season twenty vines each of Muscat Shiragai were planted at Funao Winery and the university-site vineyard, yielding approximately 41.6 kg of grapes. This initial crop forms the basis for further expansion, with 300 grafted vines planted toward the end of fiscal year 2023 and a target of surpassing 500 kg harvests by the 2028–2029 seasons. Agronomic work is underway to optimise vineyard practices including leaf removal, fertilisation and irrigation tailored to the new variety’s genetics.

Tasting notes from the university and industry partners describe the grapes as “sweet and very delicious” while the resulting wine delivers a “subtle Muscat aroma” and a smooth drinking quality. Deputy Mayor Kenji Komatsu of Kurashiki emphasised the variety’s potential to serve as a signature product of the region: “We are very much looking forward to offering a wine filled with the unique charm that can only be produced in Kurashiki.” Funao Winery’s CEO Kenichiro Miyake added that the aim is to position Muscat Shiragai as a premium branded grape linked to local terroir. OUS President Hiroyuki Hirano stressed that the collaboration between academia, industry and government is vital for building innovative local communities.

The project leadership submitted an official registration application for the new grape variety to the Ministry of Agriculture, Forestry and Fisheries at the end of 2024, and the application has been accepted with full varietal registration expected within four to five years. The strategic intent goes beyond botanical innovation, as the team frames the new grape as a driver of regional economic revitalisation through wine tourism and premium product branding.