UNEVEN SEGREGATION OF CHROMOSOMES - A POSSIBLE SOURCE OF ANEUPLOIDY IN CENCHRUS-CILIARIS (POACEAE, PANICEAE)

Natural populations of Cenchrus ciliaris L. were found to be polyploid s (4x, 5x and 6x). Quadrivalents are occasionally formed during meiosi s. Uneven segregation of chromosomes can be an important factor in the formation of aneuploid specimens in C. ciliaris. Gametes containing a n abnormal chromosome complement can lead to the formation of progeny with new aneuploid chromosome numbers. It is suggested that this meiot ic abnormality in C. ciliaris would account for aneuploid chromosome n umbers such as 2n = 30, 32, 34, 38, 40 and 42, as previously observed. It is further postulated that this species has its own limitations in the functionality of the various aneuploid gametes formed by uneven s egregation of chromosomes. When the ratios, observed during this study , are compared with all the chromosome numbers observed in the past fo r C. ciliaris, it is postulated that this species' functional range is limited to 16 and 20 chromosomes for the tetraploids, whereas for the pentaploids, it is 20 and 25.