A survey of active Uq elements in inbred lines by the use of c-ruq tester

We have reported that crosses between 11 inbred lines and the c-ruq tester only produced colorless no-spot F1 kernels, indicating a lack of any active Uq elements in these inbreds (MNL 61:5). In order to determine if there are any Uq activation events as reported by the c-ruq reporter allele, random samples of the colorless no-spot F1 kernels were taken from 7 inbred x c-ruq combinations. These kernels were grown and were tested by backcrossing to the c-ruq tester. The resulting BC1 progeny ears have been examined to generate the accompanying data.
Total number of colorless BC1 progeny kernels
Inbred Number of F1 kernels testeda no-spot few-spot (%) sectored (%)
B14 12 7,133 0 (0) 0 (0)
B37 11 7,761 0 (0) 0 (0)
B73 11 7,756 2 (0.026) 1 (0.013)
B70b 29 11,903 2 (0.017) 3 (0.025)
B70 21 9,880 0 (0) 0 (0)
C123b 24 12,692 2 (0.016) 1 (0.008)
C123 11 5,864 2 (0.034) 0 (0)
187-2b 17 9,161 1 (0.011) 1 (0.011)
187-2 24 14,687 2 (0.014) 0 (0)
C103 9 3,845 1 (0.026) 1 (0.026)
aF1 genotype: c/c-ruq(no Uq);
F1 phenotype: colorless no-spot;
bthe seedling of the inbred has been treated with 30µM 5-aza-2-deoxycytidine

Activation of Uq elements is seen as sectors of spotting in the BC1 progenies of 5 inbreds (B70, B73, C103, C123 and 187-2) with frequencies ranging from 0.8 x 10-4 to 2.5 X 10-4. No such sectors were observed in the BC1 progenies of the other 2 inbreds (B14 and B37). It is noted that this sectoring of c-ruq/Uq spots occurred in BC1 progenies of 3 inbreds after a 30 µM 5-aza-2'-deoxycytidine treatment, but not in the BC1 generation of their untreated sibs.

This study also indicates a lack of active Uq elements in the genome of the inbred B45, which has a C/C genotype (data not shown). In addition, the BC1 progenies of B45 and 2 other maize lines, M14 (wx) and M14 (Wx), are all colorless, completely lacking single-spots or sectors of spots (data not shown).

Yong-Bao Pan and Peter A. Peterson

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

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