Parental diagnosis of satsuma mandarin (Citrus unshiu Marc.) revealed by nuclear and cytoplasmic markers

Satsuma mandarins (Citrus unshiu Marc.) are the predominant cultivated citrus variety in Japan. Clarification of its origin would prove valuable for citrus taxonomy and mandarin breeding programs; however, current information is limited. We applied genome-wide genotyping using a 384 citrus single nucleotide polymorphism (SNP) array and MARCO computer software to investigate the satsuma mandarin parentage. Genotyping data from 206 validated SNPs were obtained to evaluate 67 citrus varieties and lines. A total of five parent-offspring relationships were newly found by MARCO based on the 206 SNP genotypes, indicating that 'Kishuu mikan' type mandarins (Citrus kinokuni hort. ex Tanaka accession 'Kishuu mikan' and 'Nanfengmiju') and 'Kunenbo' type mandarins (Citrus nobilis Lour. var. kunip Tanaka accession 'Kunenbo' and 'Bendiguangju') are possible parents of the satsuma mandarin. Moreover, cleaved amplified polymorphic sequences analysis showed that the genotypes of four regions in chloroplast DNA of 'Kishuu mikan' type mandarins were identical to that of the satsuma mandarin. Considering the historical background, satsuma mandarins may therefore derive from an occasional cross between a 'Kishuu mikan' type mandarin seed parent (derivative or synonym of 'Nanfengmiju') and a 'Kunenbo' type mandarin pollen parent (derivative or synonym of 'Bendiguangju').