Genome and chromosome dimensions of Lotus japonicus

Genome and chromosome dimensions were determined using two accessions of Lo tus japonicus, Miyakojima MG-20 and Gifu B-129. The genome sizes of Miyakoj ima and Gifu were determined as 472.1 and 442.8 Mbp, respectively. Both the accessions were diploid (2n=12) and six chromosomes were identified and ch aracterized based on the condensation patterns and the locations of rDNA lo ci. The obvious polymorphism observed in the genome size and the chromosome morphology between the two accessions, revealed specific accumulation of h eterochromatin in Miyakojima or elimination in Gifu. The chromosomes L. jap onicus were numbered according to their length. A quantitative chromosome m ap was also developed by the imaging methods using the digital data of the condensation pattern. 45S rDNA loci were localized on chromosomes A and F, and 5S rDNA locus was localized on chromosome A by fluorescence in situ hyb ridization (FISH). Identification of the chromosome and genome sizes and de velopment of the quantitative chromosome map represent significant contribu tion to the L. japonicus genome project as the basic information.