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United States Department of Agriculture

Agricultural Research Service

Title: Detection of Chromosome Variations in Medicago Sativa

Authors
item Bauchan, Gary
item Hossain, M. - USDA-ARS

Submitted to: Eucarpia Medicago Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 20, 1999
Publication Date: N/A

Interpretive Summary: Though the use of chromosome banding studies we have discovered a number of chromosomal variants of diploid and tetraploid alfalfa. Differences for the number, location and intensity of chromosome bands has been identified among and between accessions. Diploid ssp. falcata chromosomes possess bands primarily at the centromere. M. sativa ssp. coerulea chromosomes contain bands on their short and long arms in addition to the bands located at the centromeres. Studies of tetraploid ssp. falcata has shown that there are many more bands than would be expected. Studies on the nine germplasm sources in the U.S. for cultivated alfalfa, tetraploid ssp. sativa, have shown that the non-dormant germplasm sources have many more bands than the dormant germplasm sources. Chromosome banding has also been used to identify chromosomal abnormalities such as B-chromosomes (an extra chromosome which is smaller than the normal chromosome compliment), isochromosomes (chromosomes that have two chromosome arms which are mirro images of each other attached by a centromere), and magachromosomes (large chromosomes which maybe the result of a translocation). The C-banding technique has become a powerful cytogenetic tool for the study of alfalfa.

Technical Abstract: We have discovered using C-banding a number of chromosomal variants of diploid and tetraploid species of Medicago sativa ssp. coerulea, ssp. sativa, and ssp. falcata. Polymorphisms for the number, location and intensity of C-bands has been identified among and between accessions. Diploid ssp. falcata chromosome posses bands primarily at the centromere. M. sativa ssp. coerulea chromosomes contain bands on their short and long arms in addition to the bands located at the centromeres and NOR. Studies of tetraploid ssp. falcata has shown that there are many more bands than would be expected if tetraploid ssp. falcata is an autotetraploid. Studies on the nine germplasm sources for tetraploid ssp. sativa in the U.S. have shown that the non-dormant germplasm sources have many more bands than the dormant germplasm sources. C-banding has also been used to identify chromosomal abnormalities such as B-chromosomes (an extra chromosome which h is smaller than the normal chromosome compliment), isochromosomes (chromosomes that have two chromosome arms which are mirror images of each other attached by a centromere), and magachromosomes (large chromosomes which maybe the result of a translocation). The C-banding technique has become a powerful cytogenetic tool for the study of Medicago sativa.

Last Modified: 10/20/2014
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