FISH karyotype of nine alfalfa cultivars displayed by oligo-FISH

Cultivated alfalfa (Medicago sativa L.) is one of the most important forage crops grown all over the world. The karyotype of cultivated alfalfa based on fluorescence in situ hybridization (FISH) pattern is rarely reported. In this study, the oligonucleotide FISH (Oligo-FISH) karyotype pattern of alfalfa was obtained using probes Oligo-MsTR1, Oligo-MsCR3, Oligo-E180, 5S rDNA and 18S–26S rDNA. The results showed that 5S rDNA and 18S–26S rDNA signal distributions were conserved. Moreover, the signal patterns of the probes Oligo-E180, Oligo-MsTR1, and Oligo-MsCR3 displayed polymorphism on part of the alfalfa chromosomes. Chromosome 11 exhibits 6 variants, showing the highest polymorphism, and chromosomes 1 and 12 display 5 polymorphisms, indicating higher genetic diversity between these chromosomes. Chromosomes 3, 4, and 16 are conserved and show monomorphic, illustrating the lower genetic diversity among these three chromosomes. The level of genetic diversity can provide a theoretical basis for alfalfa hybrid breeding. In addition, the FISH karyotype of cultivated alfalfa chromosomes constructed in this study provides a reference for future analysis of alfalfa genetic stocks.