Isozyme and DNA Analyses of Local Citrus Germplasm on Amami Islands, Japan

Abstract

Genetic relationships among local Citrus accessions on the Amami islands, Japan, were evaluated using isozyme, random amplified polymorphic DNA (RAPD) and cleaved amplified polymorphic sequence (CAPS) of chloroplast DNA (cpDNA) analyses. Four loci were detected for three enzymes examined in isozyme analysis. Four and three kinds of genotypes were detected in glutamate oxaloacetate transminase (GOT)-1 and GOT-2, respectively. At least six genotypes were observed in peroxidase (PX). All accessions showed the same genotype except for one accession of superoxide dismutase (SOD)-3. In general, accessions that belong to the same species or type showed identical genotypes; however, some diversity of genotypes was observed within the same species and type. On the basis of the RAPD data, genetic relationships were assessed using NJ cluster analysis. From this result, accessions could be classified into three major clusters, A, B, and C. Cluster A included C. nobilis (Kunenbo), C. keraji (‘Keraji-Kikaijima’ and Kabuchii), C. oto (Oto), ‘Keraji-Kakeromajima’, and ‘Oto-Okinoerabujima’. Cluster B included only control accessions. Cluster C could be divided into four subclusters as follows: subcluster C. depressa (Shiikuwasha), some Sour orange relatives such as ‘Fusuu’ and ‘Kusa’, ‘Kikaimikan-Okinoerabujima’, and ‘Shimamikan’. Accessions were classified into three types in cpDNA analysis. Type I included C. nobilis (Kunenbo), C. keraji (‘Keraji-Kikaijima’ and Kabuchii), C. oto (Oto), ‘Keraji-Kakeromajima’, ‘Oto-Okinoerabujima’, and C. rokugatsu. Type II was composed of C. depressa (Shiikuwasha), ‘Kikaimikan-Okinoerabujima’, ‘Kusa’, and ‘Shiikuu’. Type III consisted of only ‘Shimamikan’. All mandarin accessions that were determined to belong to cluster A in RAPD analysis were included in type I of cpDNA analysis. Meanwhile, mandarins in types II and III in cpDNA analysis consisted of accessions in cluster C of RAPD analysis.