Identification of reciprocal translocations observed in several Melilotus species (subgenus Eumelilotus) by interspecific triple crossings

Melilotus alba differs by a reciprocal translocation from 7 other species which are categorized into M. officinalis and M. dentata groups. The two species groups, however, remained to be studied in relation to their cytological relations because of early degeneration of hybrid embryo. Interspecific triple crosses were successfully made in order to examine whether or not the reciprocal translocations observed were of the same origin. When F₁ hybrids between M. alba and M. officinalis group were crossed with M. dentata group, about a half of hybrids plants were heterozygous for a reciprocal translocation while the remaining plants were normal chromosome pairing, showing a segregation ratio of 1:1. This result indicates that reciprocal translocations observed among the three groups are of the same origin. Accordingly, it is expected that M. officinalis group and M. dentata group have the same chromosomal constitutions.