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Title: CONSTITUTIVE HETEROCHROMATIC DNA POLYMORPHISMS IN DIPLOID MEDICAGO SATIVA SSP. FALCATA.

Author
item Bauchan, Gary
item HOSSAIN, M. - UNIVERSITY OF MARYLAND

Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Falcata is a wild relative of alfalfa which is an important source of genes for the improvement of alfalfa. We do not have a chromosomal gene map of falcata thus we utilized chromosome banding techniques to identify the chromosomes of this species. This is the first report of differences in the chromosome bands which were polymorphic between accessions and within accessions. These bands could be the result of hybridization with alfalfa, thus it maybe possible for scientists to identify the regions of the subspecies falcata chromosomes which are transferred to alfalfa. Therefore the locality of important genes on the chromosomes of subspecies falcata can be identified for their transfer to alfalfa for it's improvement.

Technical Abstract: A Giemsa C-banding technique was used to study the amount and location of constitutive heterochromatin in diploid Medicago sativa ssp. falcata (L.) Arcangeli. It was found that most accessions had the typical C-banding pattern with centromeric bands on all the chromosomes and a prominent heterochromatic band at the nucleolar organizer regions (NOR) of the satellited (SAT) chromosomes. However, we observed that constitutive heterochromatic C-bands exist at the terminal ends of all the chromosomes and interstitial bands occur on both the short arm except chromosome 3 and the long arm on only chromosomes 1, 2, 3 and 6. Modified chromosomes such as isochromosomes for the short arms of chromosome 2 and 6 have been observed. B chromosomes have also been detected in two accessions of ssp. falcata. This is the first report on the existence of extensive banding polymorphisms and the detection of isochromsomes in the chromosomes of diploid ssp. falcata which could have contributed to the variation observed in cultivated alfalfa.