Forward mutation frequency of Bt in the presence of Mu

To date, the effect of Mu on the forward mutation rate of a specific locus has not been measured. In 1979 two isolation plots were set up. In one the female rows were a2 bt and the pollen rows were a purple aleurone Bt Mu stock. In the second plot the female rows also were a2 bt but the male rows were a purple aleurone Bt non-Mu stock. The frequency of bt seeds with colored aleurone in both of these plots was:
bt Total Freq. of bt
Mu 37 255,347 14.5 x 10-5
non-Mu 7 205,242 3.4 x 10-5

contingency X2 = 16-4109 (P .01 = 6.635)

There is about a fourfold higher mutation frequency in the Mu line. This difference is significant as determined by a 2 x 2 contingency X2 test. Although Mu seems to increase the forward mutation frequency of Bt the increase for this one locus is much less than the increase in the overall foward mutation frequency for seedling mutants, which is about 50-fold. This suggests that not all loci are equally sensitive to Mu.

Donald S. Robertson

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

Return to the MNL 55 On-Line Index
Return to the Maize Newsletter Index
Return to the Maize Genome Database Page