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FISH Chromosome Mapping Allowing Karyotype Analysis in Medicago truncatula Lines Jemalong J5 and R-108-1

¹Laboratoire d' Evolution et Systématique, Centre National de la Recherche Scientifique, URA 2154, Université Paris XI, Bât 362, 91405 Orsay, France; ²Institut des Sciences Végétales, Centre National de la Recherche Scientifique, UPR40, Avenue de la Terrasse, 91198 Gif-sur-Yvette CEDEX, France

Two lines of Medicago truncatula, R-108-1 and Jemalong J5, exhibit differences in their symbiotic properties, morphological markers, and capacity for regeneration and transformation. Using cytogenetic techniques, we detected differences in chromomycin A₃ staining on the two sides of the secondary constriction of the nucleolar chromosome pair of J5 and R-108-1, while DAPI (4′, 6-diamidino-2-phenylindole) staining revealed no differences between the two lines. FISH (fluorescent in situ hybridization) analysis showed a difference between J5 and R-108-1 for the same 5S rRNA genes; three loci were found in J5 but only two loci in R-108-1. However, for the 18S-5.8S-26S rDNA genes only a single locus was found in both lines. Based on these analyses, a karyotype for the two lines was established.