2022 Volume 87 Issue 2 Pages 113-118
The genus Medicago encompasses several significant and economically important annual and perennial taxa, each possessing distinct cytogenetical characteristics. Existing reports on chromosome numbers and karyology of the genus are quite intriguing and indicate the possible existence of underlying genetic variations. The present investigation on 18 taxa included three Lucerne varieties for the study of their chromosomal complements and karyological evolution. Twelve out of the 18 taxa analyzed were observed to be diploids with ten species having chromosome number of 2n=16 and two, Medicago constricta and M. rigidula contained 2n=14 chromosomes each. The remaining four species showed chromosome numbers of 2n=30 and 2n=32. Nucleolar organizing regions (NORs) have been a characteristic feature of the first pair of chromosomes in all the species analyzed. While the majority of the species analyzed show a basic number of x=8, the polybasic nature of the genus becomes apparent with x=7 and 8 and occurrence of polyploid series with 2n=14, 16, and 32. No heteromorphic pairs were observed in the chromosome complements of any of the analyzed species. This, along with the predominance of submetacentric chromosomes in the karyotypes validates the opinion that no significant structural changes have occurred to alter the karyotypes in the evolution of the genus. In the present study, numerical changes were encountered in M. arborea, M. scutellata, M. rugosa, and all three varieties of M. sativa.
