Cyto genetic studies of carthamus divaricatus with 11 pairs of chromosomes and its relationship to other carthamus species compositae
Estilai, A.; Knowles, P.F.
American Journal of Botany 63(6): 771-782
C. divaricatus (Beg. et Vacc.) Pamp., found only in Libya, has 11 pairs of chromosomes, a new chromosome number in the genus. The species is distinct morphologically. It has yellow, purple and white corollas, yellow pollen, dark-purple striped anthers, horizontal branches and strongly divaricate outer involucral bracts. The terminal portion of the middle involueral bracts is dentate and reddish brown. It is self-incompatible. Meiosis is regular in the different corolla-color types of C. divaricatus and their intraspecific hybrids. C. divaricatus was crossed to 6 spp. [C. tinctorius, C. oxyacantha, C. palaestinus, C. nitidus, C. caeruleus, C. arborescens] with n = 12, to 3 spp. [C. dentatus, C. alexandrinus, C. leucocaulos] with n = 10, to C. lanatus with n = 22, and to 2 spp. [C. baeticus, C. turkestanicus] with n = 32 chromosomes. The morphological characteristics and crossability of the parental species plus the pollen viability, seed-set, and meiotic behavior of the hybrids involving C. divaricatus and other Carthamus species indicated that C. divaricatus is very closely related to species with n = 10, closely related to C. lanatus with n = 22, and less closely related to C. tinctorius with n = 12 chromosomes. C. divaricatus seems to be distantly related to C. nitidus (n = 12). It is proposed that C. divaricatus be included provisionally with 10-chromosome species in Section II. Alternative hypotheses for the development of the 3 basic chromosome numbers are discussed.