抄録
A detailed cytological analysis of different genera of the family Cruciferae has been carried out in order to find out the role of structural differences in the phylogeny of Brassica and the allied genera. The genera studied grow wild and cultivated throughout India. The present study reveals that several chromosome numbers exist within the group of Brassica. But inspite of difference in chromosome number that there is a relationship between different genera, is quite obvious as evidence from the karyotype. The basic chromosome number for Brassica which has been assumed to be 6 is probable and intricate relationship between different genomes of this group has been suggested. The new chromosome number of Senebiera pinnatifida has been noted as n=8. An interesting correlation between diploid and polyploid species along with their ecology has been observed in Cardamine hirsuta collected from different altitude of the Himalayas has been discussed. A particular type of cytotype has been observed in Nasturtium indicum with n=12 to 24 chromosomes. The presence of 12 chromosomes in the genus Nasturtium may suggest that in the tribe Arabideae too, the basic type should be 6 as in Brassiceae.
On the basis of previous and present observation, it has been claimed that aneuploidy and diminution in chromosome size have played a significant role in evolution. But such diminution must have occurred within each of the tribes independently evolving from a common basic type. The lower or higher numbers might have had their origin from such a basic set and the diversification in number and structure of chromosomes must have evolved in parallel lines from a common basic ancestor.
