Genetic analysis of leaf isozymes in citrus.

Abstract

Leaf isozymes of four enzymes in citrus were analyzed using polyacrylamide gel electrophoresis to demonstrate the phylogenic relationship of the cultivars. Two loci for the superoxide dismutase(SOD) (EC1.15.1.1), one locus for the peroxidase (EC 1.11.1.7) and polyphenol oxidase (EC1.10.3.2), respectively were examined. In addition to the two loci of glutamate oxal-acetate transaminase(GOT) (EC2.6.1.1), reported in the former study, a new locus was detected in the present report. These experiments suggest that the mandarin cultivars originated from three genetic sources ; Indian, Chinese, and Japanese ones. Most of the Chinese mandarins including 'Kinokuni' showed identical genotypes, while the 'Ponkan' and 'Dancy tangerine' differed from the Chinese cultivars in their genotypes at the Px locus, and they were assumed to have originated from India as suggested by T. Tanaka. On the other hand, the Japanese mandarins were considered to be genetically affected by the'Chinese mandarins. But some of the Japanese mandarins including 'Yatsushiro' and 'Koji' exhibited genetic effects from Tachibana, the wild type of the mandarin in J.apan. The genotypes of the sweet orange cultivars were homogeneous and similar to those 0L the Chinese mandarins. Sour orange was heterozygous at several loci, and was assumed to be a hybrid between mandarin and pummelo. Among the pummelo cultivars, some heterogeneity was detected at some loci.