INTERSPECIFIC CROSSES INVOLVING ALFALFA. V. MEDICAGO SAXATILIS × M. SATIVA WITH REFERENCE TO M. CANCELLATA AND M. RHODOPAEA
M. saxatilis M.B. (2n = 48) could be crossed with tetraploid (2n = 32) as well as with hexaploid (2n = 48) M. sativa L. Pentaploid (2n = 40) hybrids tended to give progeny with fewer than 40 chromosomes; progenies from the hexaploid F1 tended to stabilize at hexaploid level with some fluctuations around it. At meiotic AI the hexaploid F1 showed two to five laggards in 21% of cells observed, and at AII there were 45% cells with irregular chromosome separation. M. saxatilis could be easily crossed with M. cancellata M.B. Tri-species hybrids involving M. saxatilis and M. sativa on one hand and M. cancellata or M. rhodopaea Velen. on the other hand were obtained. It is assumed that M. saxatilis has the genomic constitution S1S1 XXXX where S1 denotes homologous chromosome sets closely related to those of M. sativa s.l. The X chromosome sets probably have been derived from M. rhodopaea.