Genetic instability

Line S+40 multiple dominant A C R Pr B Pl #1877 Randolph (year 1933); produces a low frequency variation: two cases in 30 generations of the gene C to C-Im.

The aforementioned line, crossed by the activator line A C R Pr gl, gives rise to a new line which has increased mutational frequency of C to C-Im and of other characters. This C-Im mutant character segregates with non-mendelian inheritance, in the following generation segregates in a mendelian form, and in the next generation, in some cases, again segregates in a non-mendelian way.

Other heritable variation appears: A to a; R to r; sh extreme; abortive grains, big grains; small grains; crown crinkle grains; aleurone "Cocoa" colour; very intense sunred colour plant. Other confused heritable variations arise: tillering extreme; slender culm; fasciated culm; abnormal ear insertion; filodium in place of leafs and other abnormal developments.

The aforementioned events do not agree with present mathematical genetics and it could be solved with more knowledge of molecular genetics. In spite of the lack of such knowledge, these natural systems may be a useful source of characters in plant breeding.

Luis B. Mazoti

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

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