C-I changes

C-I has long been used in genetics experiments. The frequent sectoring seen when C-I is used as a male on C C is a common observation. Very likely C-I is a stable insert that only occasionally excises.

In the same isolation plot described in the report on the wx alleles (see wx report), several new C-I alleles have been rescued. There are several classes:

A. C-I-m C-I-m836526/C = Colored with colorless sectors; C-I-m836553/C = Colored with colorless sectors. Both are basic colored alleles that change to colorless (C-I). There is a remote possibility that these are basic c alleles that are mutating to C-I colorless.

B. C: C-I836683, C-I836684, C-I836685, C-I836934, C-I836955, C-1836956, C-I836958, C-I836959, C-I836960, C-I836969, C--I86970. These 11 C derivatives are seemingly stable, but some may belong to the C-I-M category.

C. C-sh: C-sh-836882/C sh = purple colored, shrunken. This is a coincident change from C-I Sh to C sh. The female transmission is normal. As with all the others of this series, each parental source ear was C-I Sh/C-I Sh.

D. C-I-unst: C-I-unst836511, C-I-unst836513, C-I-unst836518, C-I-unst836522,. C-I-unst836524, C-I-unst836811. Each of these alleles is basically C-I that is unstable, giving c_olored sectors. Some show changes to sh and bz indicating multiple loss events. Outcrosses to color lines show heavy loss of the C-I allele.

There are two new sh alleles from the same plot: sh-836660 and sh-836673. Along with the C-sh-836882 allele, the three sh alleles arose in the test plot at the rate of one in 1.3 X 106 kernels, which is a lower frequency for sh than that in the 1975 tests but close to the 1983 report (MNL57:2).

Four new c2-m alleles have been recovered and confirmed: c2-m836018, very fine, low rate; c2-m836019, very fine, low rate; c2-m836024, infrequent spots; c2-m836039, infrequent spots. These four alleles arose out of crossing block C2 C2 X c2 c2 at a rate of one per 4 x 105--a rate close to the rate of the previously rescued five c2-m alleles (MNL57:2).

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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