Karyotypes of 25 Populations of 15 Species in Allium Section Rhiziridium from China

Abstract

Karyotypes of 25 populations of 15 species in Allium section Rhiziridium from China were analyzed to discuss the evolutionary mechanisms of Allium section Rhiziridium and cytogeography of some species. Root tips for the study of mitotic chromosomes were obtained from potted plants and pretreated with paradichlorobenzene at room temperature for 9 hours. After 12-24 hours fixation in 1∶3 acetic-alcohol, the root tips were macerated in 1 mol · L-1 HC1 for 9 minutes at 60℃ and then stained and squashed in carbol fuchsin. Karyotype asymmetry was assessed by As.K%. Results showed that taxa investigated were diploid or tetraploid. Furthermore, the karyotype types were 1A, 2A or 2B according to Stebbins’ karyotype classification. Karyotypes of A.tekesicola, A.tianschanicum, A.beesianum and A.spirale were reported for the first time. Combined with previous karyotype studies, we suggested that: (1) The basic chromosome number of Allium section Rhiziridium from China is x=8. (2) The karyotype types evolutionary trend of Allium section Rhiziridium from China is 1A→2A→2B→2C . (3) Satellite chromosomes of Allium section Rhiziridium from China are varied in numbers and shapes. (4) Polyploidy and chromosome structural rearrangement are two important evolution patterns in Allium section Rhiziridium from China. (5) A.cyaneum and A.nu- tans have exploited new niches through polyploidy and asexual reproduction.