CYTOLOGICAL RELATIONSHIPS AMONG EUMELILOTUS SPECIES ANALYZED USING CYTOLOGICAL OBSERVATIONS OF INTERSPECIFIC HYBRIDS OBTAINED BY IN-VITRO CULTURE

Interspecific hybrid plants between Melilotus altissima (yellow flower s) and either M. alba (white flowers) or M. taurica (white flowers) an d between M. suaveolens (yellow flowers) and M. wolgica (white flowers ) which were inviable because of heavy chlorosis, were grown successfu lly by in vitro culture and reached the flowering stage. Pollen fertil ity of hybrid plants between M. altissima and M. alba was about 46% wh ereas hybrids between M. altissima and M. taurica and between M. suave olens and M. wolgica showed about 25% and 18% of pollen fertility, res pectively. All F(1)s did not set any selfed seeds. Observing the pairi ng of chromosomes at metaphase I in the hybrid plants, it was revealed that the genomes of M. altissima and M. alba differ by a reciprocal t ranslocation. This result could account for the partial sterility of p ollen in the F-1 hybrids. On the other hand, hybrid plants between M. altissima and M. taurica and between M. suaveolens and M. wolgica show ed normal pairing of chromosomes though pollen fertility of the hybrid s was very low, suggesting that low pollen fertility was controlled by sterility gene(s). These results demonstrate that M. altissima and 7 other species of the subgenus Eumelilotus share the same chromosomal c onstitution. The only exception, M. alba, differs from the other 8 spe cies by a segmental interchange.