Constitutive heterochromatin DNA polymorphisms in diploid Medicago sativa ssp falcata

A Giemsa C-banding technique was used to study the amount and location of c onstitutive heterochromatin in diploid (2n = 2x = 16) Medicago sativa ssp. falcata (L.) Arcangeli. Most accessions had the standard C-banding pattern with centromeric bands on all the chromosomes and a prominent heterochromat ic band at the nucleolar organizer regions (NOR) of the satellited (SAT) ch romosomes. However, we observed in various accessions that constitutive het erochromatic C-bands can exist at the telomeric ends of all the chromosomes . Interstitial bands occurred on the short arms of all chromosomes except f or chromosome 3 and on the long arms of chromosomes 1, 2, 3, and 6, only. R earranged chromosomes such as isochromosomes have been observed for the sho rt arms of chromosomes 2 and 6. This is the first report on the existence o f C-banding polymorphisms and the detection of putative isochromsomes in th e chromosomes of diploid ssp. falcata which could have contributed to the v ariation observed in cultivated alfalfa.