Swingle considered it a unique variety related to papeda, and regarded yuzu as a chance seedling of C. ichangensis. However, the allele-sharing test (from the paper "Hybrid Origins of Citrus Varieties Inferred from DNA Marker Analysis of Nuclear and Organelle Genomes"), clearly refutes this proposal, with 31 out of 123 DNA markers not shared between yuzu and C. ichangensis. These observations hypothesized that C. ichangensis could an offspring of an unidentified papeda × lemon, and yuzu might also be an offspring of this unidentified papeda. A highly aromatic, cold-tolerant citrus originating from East Asia and prized primarily for its intense fragrance, complex flavor, and culinary versatility rather than for fresh eating. It occupies a unique position between true citrus and papeda-type citrus, both genetically and horticulturally, and is one of the most important cold-hardy citrus in cultivation. Although native to China, Yuzu was domesticated and refined in Japan, where it became deeply embedded in cuisine, culture, and traditional medicine. It has been cultivated continuously for centuries, making it one of the oldest documented cold-hardy citrus in use.