Abstract
Aneuploids cannot be stably preserved by sexual propagation, though they can maintain their genetic identity by asexual propagation. However, it is possible for somaclonal variation to occur during asexual propagation. Surveys taken from 2005 to 2007 showed that there were 26 lines with morphological variations from a total of 114 asexually propagated rice lines. Among these, 12 lines were detected that had either increased or decreased chromosome numbers, while the other 14 lines did not show any changes in chromosome number. Lines with increased chromosome numbers include the following four classes: (1) an extra chromosome was retained, and another normal individual chromosome was increased; (2) an extra chromosome was increased, and the normal chromosome numbers did not change; (3) an extra chromosome was lost, and another chromosome was increased; and (4) the genome was doubled. We studied 543 somatic cells from the 12 lines during mitosis and observed abnormal mitotic behaviors such as chromosome lagging, uneven distribution, and chromosome breakage at anaphase. These results show that abnormal mitotic behavior led to the somaclonal variation in chromosome number. However, cytological variation can only explain a minority of the asexual separated lines.
Published Version
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