A survey and isozyme analysis of wild mandarin, tachibana (Citrus tachibana (Mak.) Tanaka) growing in Japan

Tachibana (Citrus tachibana (Mak.) Tanaka) trees growing in the wild and cultivated in Japan were surveyed and analyzed for their isozyme genes. Many trees were observed in south-western areas from Izu Peninsula, Shizuoka Prefecture to Ishinami, Kushima, Miyazaki Prefecture. Although most of them are cultivated, some are suggested to be wild. Isozyme analysis of the tachibana population clearly demonstrated a difference between the tachibana and mandarin cultivars introduced from China. Almost all tachibana trees examined had CC genotype atPx (peroxidase) locus, while most of the Chinese mandarins are reported to have DD at Px. In addition, an allele A at Got (glutamate oxalacetate transaminase)-2 was unique to the tachibana population. A rare allele T at Got-3, which has not been recorded in any other citrus, was found in some individuals of the tachibana population. A heterogeneity for isozyme genes was also observed in the tachibana population. These findings indicate that tachibana has been genetically isolated from other citrus in the Asian Continent, and is native to Japan. Several natural hybrids between tachibana and cultivated Chinese mandarins were found in the tachibana-growing areas.