A New Chromosone Number for the Genus Medicago1
- G. R. Bauchan and
- J. H. Elgin2
Seventy-two accessions of Medicago scutellata (L.) Mill, and 37 accessions of M. rugosa Desr. were screened to determine if diploid forms of these species exist and to observe the morphological variation within the two species. Diploid plants are desirable for crossing with both the diploid and tetraploid forms of M. sativa L. (alfalfa). The somatic chromosome number of 2n–30 was observed in all accessions of M. scutellata and M. rugosa, and no diploid forms were found. Both species contain satellited chromosomes (SAT-chromosomes), M. scutellata has two pairs of SAT-chromosomes and M. rugosa has one pair. The satellites are large and they are located a relatively long distance from the main body of the chromosome, possibly leading to the erroneous chromosome counts of 2n = 32 recorded previously. Meiosis was regular in the microspore mother cells of both species with 15 bivalents forming at metaphase I. On the basis of intraspecific variation, plants of M. scutellata could be separated into three morphological groups: 1) nonvigorous plants that flower approximately 1 month after planting and have one flower per inflorescence, 2) vigorous plants that flower 2 months after planting and have three flowers per inflorescence, and 3) an intermediate group. The way in which these 2n=30 species may have evolved and their potential value in a breeding program are suggested.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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